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Balasar Ö, Kadıoğlu Yılmaz B, Başdemirci M, Koçak Eker H, Eser Çavdartepe B, Şimşek L, Tunçez E, Duymuş F. Assessment of Pathogenic Variants in the PAH Gene and Genotype-Phenotype Correlation in Phenylketonuria Patients from Turkey. Biochem Genet 2024:10.1007/s10528-024-10892-5. [PMID: 39039323 DOI: 10.1007/s10528-024-10892-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2024] [Accepted: 07/17/2024] [Indexed: 07/24/2024]
Abstract
This study aims to determine the allele and genotype frequency, evaluate genotype-phenotype correlation and contribute to the spectrum of pathogenic variants in the PAH gene. Ninety-three individuals diagnosed with PKU were included in the study. Next-generation sequencing was utilized for detecting variants in the PAH gene. Copy Number Variations in patients without biallelic pathogenic variant were investigated by Multiplex Ligation-dependent Probe Amplification method. Genotype-phenotype correlations and genotype-based phenotype predictions were examined by comparing molecular test results with BIOPKUdb database. The clinical distributions of the patients were as follows: classic PKU 21% (n = 19), mild PKU 3% (n = 3), and mild hyperphenylalaninemia 76% (n = 71), respectively. Thirty-nine distinct variants and 70 distinct genotypes were found in patients. The most frequently observed variant was p.(Ala300Ser) (13.9%) and the most frequently observed genotype was p.[Ala300Ser];[Ala300Ser] (5.6%). Compound heterozygous genotypes (%69) were more prevalent than homozygous genotypes. A novel variant, c.441+4A>C, was observed. Predicted metabolic phenotypes in the database showed consistency with patient phenotypes (n = 33/41). BH4 responsiveness showed partial consistency with database predictions (n = 13/25). Establishing genotype-phenotype correlations can facilitate personalized management approaches. Overall, this study contributes to understanding the genetic basis and clinical course of PKU.
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Affiliation(s)
- Özgür Balasar
- Department of Medical Genetics, Konya City Hospital, Akabe Quarter, Adane Cevreyolu Street, 42020, Konya, Turkey.
| | - Banu Kadıoğlu Yılmaz
- Department of Pediatric Metabolism, Faculty of Medicine, Selçuk University, Konya, Turkey
| | - Müşerref Başdemirci
- Department of Medical Genetics, Konya City Hospital, Akabe Quarter, Adane Cevreyolu Street, 42020, Konya, Turkey
| | - Hatice Koçak Eker
- Department of Medical Genetics, Konya City Hospital, Akabe Quarter, Adane Cevreyolu Street, 42020, Konya, Turkey
| | - Büşra Eser Çavdartepe
- Department of Medical Genetics, Konya City Hospital, Akabe Quarter, Adane Cevreyolu Street, 42020, Konya, Turkey
| | - Levent Şimşek
- Department of Medical Genetics, Konya City Hospital, Akabe Quarter, Adane Cevreyolu Street, 42020, Konya, Turkey
| | - Ebru Tunçez
- Department of Medical Genetics, Konya City Hospital, Akabe Quarter, Adane Cevreyolu Street, 42020, Konya, Turkey
| | - Fahrettin Duymuş
- Department of Medical Genetics, Konya City Hospital, Akabe Quarter, Adane Cevreyolu Street, 42020, Konya, Turkey
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Alavanda C, Ceylan Eİ, Kılavuz S, Çıkı K. Comprehensive analyses of phenylalanine hydroxylase variants and phenotypic characteristics of patients in the eastern region of Türkiye. J Pediatr Endocrinol Metab 2024; 37:543-552. [PMID: 38706300 DOI: 10.1515/jpem-2024-0091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2024] [Accepted: 04/17/2024] [Indexed: 05/07/2024]
Abstract
OBJECTIVES Phenylalanine hydroxylase (PAH) is predominantly a hepatic enzyme that catalyzes phenylalanine (Phe) into tyrosine, which is the rate-limiting step in Phe catabolism. Biallelic variants in the PAH gene cause PAH enzyme deficiency. Phenylketonuria (PKU) is an autosomal recessive disorder that causes neurologic, behavioral, and dermatological findings. PKU could be divided clinically into three types based on the blood Phe levels: classic phenylketonuria (cPKU), mild-moderate phenylketonuria (mPKU), and mild hyperphenylalaninemia (MHP). This study aimed to determine the phenotypic and genotypic characteristics of Turkish PKU patients in the eastern region of Türkiye. METHODS Demographic characteristics, serum Phe levels, treatments, and PAH variants of 163 patients with PKU and hyperphenylalaninemia (HPA) were retrospectively evaluated. Blood Phe levels of the patients were analyzed with the high-performance liquid chromatography method. For PAH gene analysis, next-generation sequencing was performed. RESULTS Of the 163 patients included in the study, 38 (23.3 %) had cPKU, 16 (9.8 %) had mPKU, and 109 (66.9 %) had MHP. Homozygous variants in the PAH gene were detected in 66 (40.5 %) of the patients, while compound heterozygous variants were detected in 97 (59.5 %) patients. Two novel and 35 recurrent variants in the PAH gene were detected. Of the two novel variants, one was missense (p.Phe351Leu) and the other was frameshift (p.Met276Cysfs*65). The most frequently detected variants were p.Thr380Met (18 %), p.Arg261Gln (16.8 %), and p.Ala300Ser (12.8 %). All patients with the homozygous c.1066-11G>A variant exhibited cPKU phenotype. The c.898G>T (p.Ala300Ser), c.1139C>T (p.Thr380Met), and c.1208C>T (p.Ala403Val) variants were statistically related to mild phenotype. On the other hand, c.592_613del (p.Tyr198Serfs*136), c.1028A>G (p.Tyr343Cys), and c.782G>A (p.Arg261Gln) variants were more frequently detected in the cPKU group. CONCLUSIONS Our study, conducted with patients from the eastern region of Türkiye, demonstrates the genetic heterogeneity in the Turkish population. Simultaneously, our research contributes to genotype-phenotype correlation and expands the genotypic spectrum by identifying novel variants.
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Affiliation(s)
- Ceren Alavanda
- Department of Medical Genetics, Van Research and Training Hospital, Van, Türkiye
| | - Emine İpek Ceylan
- Department of Medical Genetics, Van Research and Training Hospital, Van, Türkiye
- Department of Medical Genetics, Dr Abdurrahman Yurtaslan Ankara Oncology Education and Research Hospital, Ankara, Türkiye
| | - Sebile Kılavuz
- Division of Child Nutrition and Metabolism, Department of Pediatrics, School of Medicine, Marmara University, İstanbul, Türkiye
- Division of Child Nutrition and Metabolism, Department of Pediatrics, Van Research and Training Hospital, Van, Türkiye
| | - Kısmet Çıkı
- Division of Child Nutrition and Metabolism, Department of Pediatrics, Van Research and Training Hospital, Van, Türkiye
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Shyam R, Sekhar Panda H, Mishra J, Jyoti Panda J, Kour A. Emerging biosensors in Phenylketonuria. Clin Chim Acta 2024; 559:119725. [PMID: 38734223 DOI: 10.1016/j.cca.2024.119725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 05/07/2024] [Accepted: 05/08/2024] [Indexed: 05/13/2024]
Abstract
Phenylketonuria (PKU) is an autosomal recessive metabolic disorder resulting from deficient phenylalanine hydroxylase (PAH) enzyme activity, leading to impaired phenylalanine (Phe) metabolism. This condition can lead to intellectual disability, epilepsy, and behavioural issues. Treatment typically involves strict dietary restrictions on natural protein intake, supplemented with chemically manufactured protein substitutes containing amino acids other than Phe. Various approaches, including casein glycomacropeptide (GMP), tetrahydrobiopterin (BH4), phenylalanine ammonia-lyase (PAL) therapy, large neutral amino acid (LNAA) supplementation, enzyme therapy, gene therapy, and medical therapies, aim to prevent Phe transport in the brain to potentially treat PKU. Although newborn screening programs and early dietary interventions have enhanced outcomes of the potential treatment strategies, limitations still persist in this direction. These involve potent accuracy concerns in diagnosis due to the existence of antibiotics in blood of PKU patients, affecting growth of the bacteria in the bacterial inhibition assay. Monitoring involves complex methods for instance, mass spectrometry and high-pressure liquid chromatography, which involve shortcomings such as lengthy protocols and the need for specialized equipment. To address these limitations, adaptable testing formats like bio/nano sensors are emerging with their cost-effectiveness, biodegradability, and rapid, accurate, and sensitive detection capabilities, offering promising alternatives for PKU diagnosis. This review provides insights into current treatment and diagnostic approaches, emphasizing on the potential applications of the diverse sensors intended for PKU diagnosis.
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Affiliation(s)
- Ritika Shyam
- University Institute of Pharma Sciences, Chandigarh University, Gharuan, Mohali, Punjab 140413, India
| | | | - Jibanananda Mishra
- School of Biosciences, RIMT University, Mandi Gobindgarh, Punjab 147301, India
| | - Jiban Jyoti Panda
- Institute of Nanoscience and Technology, Mohali, Punjab 140306, India.
| | - Avneet Kour
- University Institute of Pharma Sciences, Chandigarh University, Gharuan, Mohali, Punjab 140413, India.
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Kadıoğlu Yılmaz B, Bağcı Z. Delays in Newborn Screening for Phenylketonuria from Birth to Diagnosis and Factors Affecting This. CHILDREN (BASEL, SWITZERLAND) 2024; 11:571. [PMID: 38790566 PMCID: PMC11120001 DOI: 10.3390/children11050571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2024] [Revised: 04/12/2024] [Accepted: 05/08/2024] [Indexed: 05/26/2024]
Abstract
This study aims to evaluate the process of neonatal phenylketonuria (PKU) screening from birth to admission to the pediatric metabolism polyclinic, determining delays in the screening program and the factors influencing them. This study was conducted during 2021-2023. Blood collection dates, results, and probable parameters causing delays in the screening program were recorded. This study included 118 infants. Admission time to the polyclinic was (mean ± SD) 25.2 ± 12.6 days (min-max: 3.4-78.9 days). Admission time was significantly high for refugees, those whose parents were consanguineous, and those who had more heel-prick blood samples taken (p < 0.001, p = 0.005, and p < 0.001, respectively). The first heel-prick blood phenylalanine (phe) level was significantly negatively correlated with the admission time (p < 0.001). Patients' admission time whose first blood phe level < 240 μmol/L was statistically significantly higher than in those with ≥240 μmol/L (p < 0.001). We determined that there were delays in PKU screening from birth to admission to the polyclinic. Being a refugee, the presence of consanguineous marriages, the increase in the number of heel-prick tests, and blood phe levels at a range of 120-240 μmol/L were the factors that played a role in this delay. Taking steps to reduce the impact of these parameters can prevent delays in newborn PKU screening and increase the success of the screening program.
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Affiliation(s)
- Banu Kadıoğlu Yılmaz
- Department of Pediatric Metabolism, Konya City Hospital, University of Health Sciences, Konya 42020, Türkiye
- Department of Pediatric Nutrition and Metabolism, Faculty of Medicine, Selçuk University, Konya 42250, Türkiye
| | - Zafer Bağcı
- Department of Pediatrics, Konya City Hospital, University of Health Sciences, Konya 42020, Türkiye;
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Çıkı K, Yıldız Y, Kahraman AB, Özgül RK, Coşkun T, Dursun A, Tokatlı A, Sivri S. Predictors of eventual requirement of phenylalanine-restricted diet in young infants with phenylalanine hydroxylase deficiency initially managed with sapropterin monotherapy. Mol Genet Metab 2023; 140:107706. [PMID: 37837865 DOI: 10.1016/j.ymgme.2023.107706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Revised: 10/02/2023] [Accepted: 10/02/2023] [Indexed: 10/16/2023]
Abstract
BACKGROUND Phenylalanine (Phe)-restricted diet is associated with lower quality of life for patients with phenylketonuria (PKU), and a concern for caregivers of recently-diagnosed infants. Sapropterin is an oral drug used as an alternative or adjunct to dietary treatment. We have observed that some of the young infants initially managed successfully with sapropterin monotherapy have required dietary treatment in long-term follow-up. We aimed to determine the baseline factors associated with future initiation of dietary treatment in these patients. METHODS Data were obtained retrospectively from the medical records of 80 PKU patients started on sapropterin monotherapy before 3 months of age between 2011 and 2021. RESULTS The patients were followed for a median of 3.9 years (Q1-Q3: 2.5-5.75 years). Sapropterin was tapered down and discontinued in 5 patients (6.3%) as their Phe levels remained below 360 μmol/L without treatment. Sapropterin monotherapy was sufficient in 62 patients (77.5%), while 13 (16.2%) required dietary treatment. Phe and tyrosine (Tyr) levels, and Phe:Tyr ratios differed significantly among the patients maintained on sapropterin monotherapy and those started on dietary treatment, but the Phe:Tyr ratio at diagnosis was the most important independent baseline variable (OR: 1.61, 95% CI: 1.15-2.27, p = 0.006), with Phe:Tyr ratio at diagnosis >5.25 associated with dietary treatment (sensitivity: 90.0%, specificity: 81.8%). Genotypic phenotype value (GPV), unavailable at baseline, was also associated with dietary treatment (median GPV 9.2 vs. 3.8, p = 0.006), but some genotypes were not specific to the final treatment modality. DISCUSSION We propose that the Phe:Tyr ratio at diagnosis is an important indicator to predict dietary requirement in young infants initially managed with sapropterin monotherapy.
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Affiliation(s)
- Kısmet Çıkı
- Division of Pediatric Metabolism, Department of Pediatrics, Faculty of Medicine, Hacettepe University, Ankara, Turkey.
| | - Yılmaz Yıldız
- Division of Pediatric Metabolism, Department of Pediatrics, Faculty of Medicine, Hacettepe University, Ankara, Turkey.
| | - Ayça Burcu Kahraman
- Division of Pediatric Metabolism, Department of Pediatrics, Faculty of Medicine, Hacettepe University, Ankara, Turkey.
| | - R Köksal Özgül
- Hacettepe University Institute of Child Health, Ankara, Turkey.
| | - Turgay Coşkun
- Division of Pediatric Metabolism, Department of Pediatrics, Faculty of Medicine, Hacettepe University, Ankara, Turkey.
| | - Ali Dursun
- Division of Pediatric Metabolism, Department of Pediatrics, Faculty of Medicine, Hacettepe University, Ankara, Turkey.
| | - Ayşegül Tokatlı
- Division of Pediatric Metabolism, Department of Pediatrics, Faculty of Medicine, Hacettepe University, Ankara, Turkey.
| | - Serap Sivri
- Division of Pediatric Metabolism, Department of Pediatrics, Faculty of Medicine, Hacettepe University, Ankara, Turkey.
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Ajami N, Soleimani A, Jafarzadeh‐Esfehani R, Hasanpour M, Rashid Shomali R, Abbaszadegan MR. Mutational landscape of phenylketonuria in Iran. J Cell Mol Med 2023; 27:2457-2466. [PMID: 37525467 PMCID: PMC10468661 DOI: 10.1111/jcmm.17865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 06/11/2023] [Accepted: 06/28/2023] [Indexed: 08/02/2023] Open
Abstract
To date more than 1000 different variants in the PAH gene have been identified in patients with phenylketonuria (PKU). In Iran, several studies have been performed to investigate the genetics bases of the PKU in different parts of the country. In this study, we have analysed and present an update of the mutational landscape of the PAH gene as well as the population genetics and frequencies of detected variants for each cohort. Published articles on PKU mutations in Iran were identified through a comprehensive PubMed, Google Scholar, Web of Science (ISI), SCOPUS, Elsevier, Wiley Online Library and SID literature search using the terms: "phenylketonuria", "hyperphenylalaninemia", and "PKU" in combination with "Iran", "Iranian population", "mutation analysis", and "Molecular genetics". Among the literature-related to genetics of PKU, 18 studies were on the PKU mutations. According to these studies, in different populations of Iran 1497 patients were included for mutation detection that resulted in detection of 129 different mutations. Results of genetic analysis of the different cohorts of Iranian PKU patients show that the most prevalent mutation in Iran is the pathogenic splice variant c.1066-11G > A, occurring in 19.54% of alleles in the cohort. Four other common mutations were p.Arg261Gln, p.Pro281Leu, c.168 + 5G > C and p.Arg243Ter (8.18%, 6.45%, 5.88% and 3.7%, respectively). One notable feature of the studied populations is its high rate of consanguineous marriages. Considering this feature, determining the prevalent PKU mutations could be advantageous for designing screening and diagnostic panels in Iran.
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Affiliation(s)
- Naser Ajami
- Department of Medical Genetics and Molecular Medicine, School of MedicineMashhad University of Medical SciencesMashhadIran
- Medical Genetics Research Center, School of MedicineMashhad University of Medical SciencesMashhadIran
| | - Anvar Soleimani
- Department of Medical Microbiology, College of Health SciencesCihan University‐ SulaimaniyaSulaimaniyaIraq
| | - Reza Jafarzadeh‐Esfehani
- Blood Borne Infections Research Center, Academic Center for EducationCulture and Research (ACECR)‐ Khorasan RazaviMashhadIran
| | - Mojtaba Hasanpour
- Department of Biology, Faculty of SciencesUniversity of GuilanRashtIran
| | - Romina Rashid Shomali
- Reproductive Health Research Center, Department of Obstetrics and Gynecology, Alzahra HospitalGuilan University of Medical SciencesRashtIran
| | - Mohammad Reza Abbaszadegan
- Department of Medical Genetics and Molecular Medicine, School of MedicineMashhad University of Medical SciencesMashhadIran
- Immunology Research CenterMashhad University of Medical SciencesMashhadIran
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Alghamdi MA, O'Donnell‐Luria A, Almontashiri NA, AlAali WY, Ali HH, Levy HL. Classical phenylketonuria presenting as maternal PKU syndrome in the offspring of an intellectually normal woman. JIMD Rep 2023; 64:312-316. [PMID: 37701331 PMCID: PMC10494492 DOI: 10.1002/jmd2.12384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 07/06/2023] [Accepted: 07/11/2023] [Indexed: 09/14/2023] Open
Abstract
Phenylketonuria (PKU) is an autosomal recessive inborn error of metabolism resulting from a deficiency of phenylalanine hydroxylase (PAH). If untreated by dietary restriction of phenylalanine intake, impaired postnatal cognitive development results from the neurotoxic effects of excessive phenylalanine (Phe). Signs and symptoms include severe intellectual disability and behavior problems with a high frequency of seizures and variable microcephaly. Maternal PKU syndrome refers to fetal damage resulting in congenital abnormalities when the mother has untreated PKU during pregnancy. Here, we report an intellectually normal 32-year-old female who presented with recurrent pregnancy loss and two neonatal deaths with congenital heart disease, microcephaly, intrauterine growth restriction, and respiratory distress. She was diagnosed with PKU through exome sequencing performed for carrier testing with a homozygous pathogenic variant in the PAH gene, c.169_171del, p.(Glu57del) that is associated with classical PKU. Consistent with the genetic finding, she had a markedly increased plasma phenylalanine concentration of 1642 μmol/L (normal <100). This case demonstrates that recurrent pregnancy loss due to untreated maternal PKU may present as an initial finding in otherwise unsuspected classical PKU and illustrates that extreme degrees of variable expressivity may occur in classical PKU. Moreover, this case illustrates the value of genomic sequencing of women who experience recurrent pregnancy loss or neonatal anomalies.
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Affiliation(s)
- Malak Ali Alghamdi
- Harvard Medical SchoolBostonMassachusettsUSA
- Medical Genetic Division, Pediatric DepartmentCollege of Medicine, King Saud UniversityRiyadhSaudi Arabia
- Program in Medical and Population GeneticsBroad Institute of MIT and HarvardCambridgeMassachusettsUSA
| | - Anne O'Donnell‐Luria
- Harvard Medical SchoolBostonMassachusettsUSA
- Program in Medical and Population GeneticsBroad Institute of MIT and HarvardCambridgeMassachusettsUSA
- Division of Genetics and GenomicsBoston Children's HospitalBostonMassachusettsUSA
| | - Naif A. Almontashiri
- Center for Genetics and Inherited Diseases (CGID)Taibah UniversityMadinahSaudi Arabia
| | - Wajeih Y. AlAali
- Dr. Sulaiman Al Habib Medical GroupArryan HospitalRiyadhSaudi Arabia
| | - Hebatallah H. Ali
- Research Center, College of MedicineKing Saud UniversityRiyadhSaudi Arabia
| | - Harvey L. Levy
- Harvard Medical SchoolBostonMassachusettsUSA
- Program in Medical and Population GeneticsBroad Institute of MIT and HarvardCambridgeMassachusettsUSA
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Khalil A, Amin E, Alrafay SSE, Khalifa OA. The effects of a self-learning package on mothers' knowledge and practices towards caring for their children with phenylketonuria. J Med Life 2023; 16:215-219. [PMID: 36937487 PMCID: PMC10015575 DOI: 10.25122/jml-2022-0258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 12/06/2022] [Indexed: 03/21/2023] Open
Abstract
The objective of this study was to evaluate the effect of a self-learning package on mothers' knowledge and practices towards caring for their children with phenylketonuria. A pre/post quasi-experimental study was conducted, including 128 mothers of children diagnosed with phenylketonuria. A specifically designed and validated questionnaire was used to evaluate mothers' knowledge and reported practices toward their children before and after participating in the educational program. There was a highly positive association between knowledge and reported practice (.674 and .398). The self-learning package had a positive impact on mothers' knowledge and practices. Consequently, educational programs should be provided to all mothers of newly diagnosed cases to improve their children's adherence to the therapeutic regimen.
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Affiliation(s)
- Amira Khalil
- Pediatric Nursing Department, Faculty of Nursing, Ain Shams University, Cairo, Egypt
- Corresponding Author: Amira Khalil, Pediatric Nursing Department, Faculty of Nursing, Ain Shams University, Cairo, Egypt. E-mail:
| | - Eman Amin
- Pediatric Nursing Department, Faculty of Nursing, Ain Shams University, Cairo, Egypt
| | | | - Ola Ali Khalifa
- Medical Genetics Department, Faculty of Medicine, Ain Shams University, Cairo, Egypt
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Elhawary NA, AlJahdali IA, Abumansour IS, Elhawary EN, Gaboon N, Dandini M, Madkhali A, Alosaimi W, Alzahrani A, Aljohani F, Melibary EM, Kensara OA. Genetic etiology and clinical challenges of phenylketonuria. Hum Genomics 2022; 16:22. [PMID: 35854334 PMCID: PMC9295449 DOI: 10.1186/s40246-022-00398-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 07/08/2022] [Indexed: 02/08/2023] Open
Abstract
This review discusses the epidemiology, pathophysiology, genetic etiology, and management of phenylketonuria (PKU). PKU, an autosomal recessive disease, is an inborn error of phenylalanine (Phe) metabolism caused by pathogenic variants in the phenylalanine hydroxylase (PAH) gene. The prevalence of PKU varies widely among ethnicities and geographic regions, affecting approximately 1 in 24,000 individuals worldwide. Deficiency in the PAH enzyme or, in rare cases, the cofactor tetrahydrobiopterin results in high blood Phe concentrations, causing brain dysfunction. Untreated PKU, also known as PAH deficiency, results in severe and irreversible intellectual disability, epilepsy, behavioral disorders, and clinical features such as acquired microcephaly, seizures, psychological signs, and generalized hypopigmentation of skin (including hair and eyes). Severe phenotypes are classic PKU, and less severe forms of PAH deficiency are moderate PKU, mild PKU, mild hyperphenylalaninaemia (HPA), or benign HPA. Early diagnosis and intervention must start shortly after birth to prevent major cognitive and neurological effects. Dietary treatment, including natural protein restriction and Phe-free supplements, must be used to maintain blood Phe concentrations of 120-360 μmol/L throughout the life span. Additional treatments include the casein glycomacropeptide (GMP), which contains very limited aromatic amino acids and may improve immunological function, and large neutral amino acid (LNAA) supplementation to prevent plasma Phe transport into the brain. The synthetic BH4 analog, sapropterin hydrochloride (i.e., Kuvan®, BioMarin), is another potential treatment that activates residual PAH, thus decreasing Phe concentrations in the blood of PKU patients. Moreover, daily subcutaneous injection of pegylated Phe ammonia-lyase (i.e., pegvaliase; PALYNZIQ®, BioMarin) has promised gene therapy in recent clinical trials, and mRNA approaches are also being studied.
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Affiliation(s)
- Nasser A. Elhawary
- grid.412832.e0000 0000 9137 6644Department of Medical Genetics, College of Medicine, Umm Al-Qura University, P.O. Box 57543, Mecca, 21955 Saudi Arabia
| | - Imad A. AlJahdali
- grid.412832.e0000 0000 9137 6644Department of Community Medicine, College of Medicine, Umm Al-Qura University, P.O. Box 57543, Mecca, 21955 Saudi Arabia
| | - Iman S. Abumansour
- grid.412832.e0000 0000 9137 6644Department of Medical Genetics, College of Medicine, Umm Al-Qura University, P.O. Box 57543, Mecca, 21955 Saudi Arabia
| | - Ezzeldin N. Elhawary
- grid.123047.30000000103590315Faculty of Medicine, MS Genomic Medicine Program, University of Southampton, Southampton General Hospital, Southampton, UK
| | - Nagwa Gaboon
- grid.7269.a0000 0004 0621 1570Department of Clinical Genetics, Faculty of Medicine, Ain Shams University, Cairo, Egypt
| | - Mohammed Dandini
- Department of Laboratory and Blood Bank, Maternity and Children Hospital, Mecca, Saudi Arabia
| | - Abdulelah Madkhali
- grid.415254.30000 0004 1790 7311Department of Pathology and Laboratory Medicine, King Abdulaziz Medical City, Ministry of National Guard Health Affairs, Riyadh, Saudi Arabia
| | - Wafaa Alosaimi
- Department of Hematology, Maternity and Children Hospital, Mecca, Saudi Arabia
| | - Abdulmajeed Alzahrani
- Department of Laboratory and Blood Bank at Maternity and Children Hospital, Mecca, Saudi Arabia
| | - Fawzia Aljohani
- Department of Pediatric Clinics, Maternity and Children Hospital, King Salman Medical City, Madinah, Saudi Arabia
| | - Ehab M. Melibary
- grid.412832.e0000 0000 9137 6644Department of Medical Genetics, College of Medicine, Umm Al-Qura University, P.O. Box 57543, Mecca, 21955 Saudi Arabia
| | - Osama A. Kensara
- grid.412832.e0000 0000 9137 6644Department of Clinical Nutrition, Faculty of Applied Medical Sciences, Umm Al-Qura University, Jeddah, Saudi Arabia
- Department of Biochemistry, Batterjee Medical College, Jeddah, Saudi Arabia
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Ozturk FN, Akin Duman T. An update of the mutation spectrum of phenylalanine hydroxylase (PAH) gene in the population of Turkey. J Pediatr Endocrinol Metab 2022; 35:663-668. [PMID: 35405047 DOI: 10.1515/jpem-2021-0556] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 03/09/2022] [Indexed: 11/15/2022]
Abstract
Phenylketonuria (PKU) is an autosomal recessive disorder of phenylalanine metabolism, mostly caused by PAH gene variants. The aim of this study was to identify the frequency of PAH gene variants in Turkish population with PKU. In 433 patients with PKU, PAH gene was examined using next generation sequencing (NGS) method. IVS10- 11G>A, p.R261Q, p.A300S, p.A403V, and p.T380 variants, which are the most common variants in this study, constituted 45,9% of the variants in our study. Nine novel variants p.A34V, K73Qfs*4, R157H, R261S, p.T266I, p.S310P, T328A, p.F351I, and K363N were identified. This study determines the most common PAH variants in Turkey and shows that PKU can be screened before marriage with the screening kits. Identification of the PAH gene variant spectrum is important for early diagnosis, understanding molecular mechanisms, clinical follow-up, treatment, and genetic counseling. And the novel variants found this study are important for further studies.
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Affiliation(s)
- Fatma Nihal Ozturk
- Department of Medical Genetics, Istanbul Haseki Training and Research Hospital, Istanbul, Turkey
| | - Tugba Akin Duman
- Department of Medical Genetics, Istanbul Haseki Training and Research Hospital, Istanbul, Turkey
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11
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Çınar M, Kılıç Yıldırım G, Kocagil S, Çilingir O. Spectrum of PAH gene mutations and genotype-phenotype correlation in patients with phenylalanine hydroxylase deficiency from Turkey. J Pediatr Endocrinol Metab 2022; 35:639-647. [PMID: 35355500 DOI: 10.1515/jpem-2022-0047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 03/07/2022] [Indexed: 11/15/2022]
Abstract
OBJECTIVES The aim of our study was to define the genotype-phenotype correlations of mutations in the PAH gene among the Turkey's Central Anatolian region. METHODS Demographic characteristics of 108 patients with hyperphenylalaninemia (HPA) and 94 patients whose diagnosis was confirmed by PAH gene analysis (Sanger DNA Sequence Analysis and Next-Generation Sequencing) were determined retrospectively. Blood phenylalanine levels were analyzed using the high-performance liquid chromatography method. RESULTS Mild HPA-not-requiring-treatment (NT) was found in 50.9% of the patients, and a classical phenylketonuria (PKU) phenotype was found in 25.9%. Forty-seven types of variants were identified. The predominant variants were p.Ala403Val (9.9%), p.Ala300Ser (9.4%), and c.1066-11G>A (splicing) (9.4%). Missense mutations accounted for 68% of mutations and attenuated the clinical impact; splice variations were found in 14.8% of cases with severe features. The p.Thr380Met allele was specific to the mild HPA-NT group. The c.1066-11G>A (splicing) allele was associated with classical PKU, whereas the p.Arg408Trp allele was linked to severe symptoms. Three variations of unknown clinical significance were discovered: c.706+4A>T (splicing), c.843-5T>C (splicing), and p.Thr323=. Of these variants, the patient who was homozygous for the c.843-5T>C (splicing) allele related to the classical PKU phenotype. 70% of the patients who underwent tetrahydrobiopterin (BH4) test were responsive. Phenotypes that responded to BH4 treatment were mostly mild phenotypes. CONCLUSIONS The PAH genotype is the main factor that determines the phenotype of PKU. Establishing the relationship between the identified genetic mutations and phenotypic characteristics will provide very important data for each patient in terms of the specific management style.
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Affiliation(s)
- Müge Çınar
- Pediatrics, Bozüyük State Hospital, Bilecik, Turkey
| | - Gonca Kılıç Yıldırım
- Department of Paediatrics, Eskisehir Osmangazi University Faculty of Medicine, Division of Child Nutrition and Metabolism, Eskisehir, Turkey
- Eskisehir Osmangazi University Faculty of Medicine, Meselik Campuse, Odunpazari, Turkey
| | - Sinem Kocagil
- Eskisehir Osmangazi University Faculty of Medicine, Meselik Campuse, Odunpazari, Turkey
- Department of Genetics and Genomics Medicine, Eskisehir Osmangazi University Faculty of Medicine, Eskisehir, Turkey
| | - Oğuz Çilingir
- Eskisehir Osmangazi University Faculty of Medicine, Meselik Campuse, Odunpazari, Turkey
- Department of Genetics and Genomics Medicine, Eskisehir Osmangazi University Faculty of Medicine, Eskisehir, Turkey
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12
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Alibakhshi R, Mohammadi A, Salari N, Khamooshian S, Kazeminia M, Moradi K. Spectrum of PAH gene mutations in 1547 phenylketonuria patients from Iran: a comprehensive systematic review. Metab Brain Dis 2021; 36:767-780. [PMID: 33625639 DOI: 10.1007/s11011-021-00698-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Accepted: 02/16/2021] [Indexed: 12/12/2022]
Abstract
As one of the highest prevalence rates in the world, the prevalence of Phenylketonuria (PKU) in Iran has been estimated at 16.5 per 100,000 neonates. The objective of this study was to evaluate the spectrum and frequency of mutations of the phenylalanine hydroxylase (PAH) gene in Iranian PKU patients. A systematic review was carried out on previous studies on PAH gene mutations in Iranian PKU patients. A complete search was carried out on the on-line databases of Scopus, Web of Science, PubMed/Medline, ProQuest, Science Direct, Magiran, SID and the search engine Google Scholar. The keywords of Phenylketonuria, PKU, Phenylalanine Hydroxylase, PAH, and Iran, as well as their Persian equivalents, in all possible combinations were used. Finally, a total of 21 eligible articles with a sample size of 1547 Iranian PKU patients, published between 2003 and 2020, were included in our systematic review. A total of 129 different PAH gene mutations including, IVS10-11G > A (c.1066-11G > A) (19.23%), p.R261Q (c.782G > A) (7.63%), p.P281L (c.842C > T) (6.24%), IVS2 + 5G > C (c.168 + 5G > C) (5.75%), p.R243* (c.727C > T) (3.59%), IVS9 + 5G > A (c.969 + 5G > A) (2.84%), p.R176* (c.526C > T) (2.42%), p.Lys363Nfs*37 (c.1089delG) (2.13%), IVS11 + 1G > C (c.1199 + 1G > C) (2.07%) and p.L48S (c.143 T > C) (2.04%) were identified. The spectrum and frequency of mutations observed in Iran were closer to those observed in the Mediterranean countries. Our results are valuable in planning panel-based studies in provinces with incomplete data on PAH gene mutations. This study is a good reference for genetic counselors and physicians who advise couples in making decisions to maintain or terminate a pregnancy.
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Affiliation(s)
- Reza Alibakhshi
- Department of Biochemistry, School of Medicine, Kermanshah University of Medical Sciences, Parastar Street, Kermanshah, Kermanshah Province, Iran
| | - Aboozar Mohammadi
- Student Research Committee, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Nader Salari
- Department of Biostatistics, School of Health, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Sahand Khamooshian
- Student Research Committee, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Mohsen Kazeminia
- Student Research Committee, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Keivan Moradi
- Department of Biochemistry, School of Medicine, Kermanshah University of Medical Sciences, Parastar Street, Kermanshah, Kermanshah Province, Iran.
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13
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Phenylketonuria Diagnosis by Massive Parallel Sequencing and Genotype-Phenotype Association in Brazilian Patients. Genes (Basel) 2020; 12:genes12010020. [PMID: 33375644 PMCID: PMC7824641 DOI: 10.3390/genes12010020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 12/21/2020] [Accepted: 12/22/2020] [Indexed: 12/04/2022] Open
Abstract
Phenylketonuria (PKU) is a common inborn error of amino acid metabolism in which the enzyme phenylalanine hydroxylase, which converts phenylalanine to tyrosine, is functionally impaired due to pathogenic variants in the PAH gene. Thirty-four Brazilian patients with a biochemical diagnosis of PKU, from 33 unrelated families, were analyzed through next-generation sequencing in the Ion Torrent PGM™ platform. Phenotype–genotype correlations were made based on the BioPKU database. Three patients required additional Sanger sequencing analyses. Twenty-six different pathogenic variants were identified. The most frequent variants were c.1315+1G>A (n = 8/66), c.473G>A (n = 6/66), and c.1162G>A (n = 6/66). One novel variant, c.524C>G (p.Pro175Arg), was found in one allele and was predicted as likely pathogenic by the American College of Medical Genetics and Genomics (ACMG) criteria. The molecular modeling of p.Pro175Arg indicated that this substitution can affect monomers binding in the PAH tetramer, which could lead to a change in the stability and activity of this enzyme. Next-generation sequencing was a fast and effective method for diagnosing PKU and is useful for patient phenotype prediction and genetic counseling.
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14
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Jafarzadeh-Esfehani R, Vojdani S, Hashemian S, Mirinezhad M, Pourafshar M, Forouzanfar N, Zargari S, Jaripour ME, Sadr-Nabavi A. Genetic variants of the phenylalanine hydroxylase gene in patients with phenylketonuria in the northeast of Iran. J Pediatr Endocrinol Metab 2020; 33:355-359. [PMID: 32069237 DOI: 10.1515/jpem-2019-0351] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 01/06/2020] [Indexed: 11/15/2022]
Abstract
Background Phenylketonuria (PKU) is a common metabolic disorder with great burden if left untreated or undiagnosed. Genetic variations in the phenylalanine hydroxylase (PAH) gene may be widely varied across different regions of a country. By knowing the most common mutations, diagnostic work-ups will be offered sooner and with lower costs for patients. The present study defines the most common genetic variations in the PAH gene in Khorasan province of Iran. Methods The present cross-sectional study took place in Khorasan province of Iran within a 6-year period starting from 2012 to 2018. Every patient who had been referred as suspicious PKU cases or referred for prenatal diagnosis was included in the present study. Results A total number of 122 individuals with a mean age of 26.22 years were enrolled in the present study. The most frequent genetic variations in the PAH gene were c.1066-11G > A and c.143 T > C. Exon 7 carried the most genetic variations compared to any single exon. Also, three patients had compound heterozygous status for c.727 C > T/c.1066-11 G > A in exon 7 and 11 of the PAH gene. Conclusions Mutations in the PAH gene are widely varied among different populations, and our results confirmed this fact. Determination of the most prevalent mutations and polymorphisms in each region will reduce the time and cost of diagnosing such preventable diseases and will therefore reduce the disease burden.
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Affiliation(s)
- Reza Jafarzadeh-Esfehani
- Department of Medical Genetics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Samaneh Vojdani
- Department of Medical Genetics, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Somayyeh Hashemian
- Department of Pediatric Diseases, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Mohammadreza Mirinezhad
- Department of Medical Genetics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | | | - Narjes Forouzanfar
- Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
| | - Selma Zargari
- Department of Medical Genetics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | | | - Ariane Sadr-Nabavi
- Department of Medical Genetics, Faculty of Medicine, Mashhad University of Medical Sciences, Azadi Square, Mashhad, Iran.,Academic Center for Education, Culture and Research (ACECR)-Khorasan Razavi, Mashhad, Iran, Phone: 09155570305, 05138827046
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15
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Gundorova P, Kuznetsova IA, Agladze D, Margvelashvili L, Kldiashvili E, Kvlividze O, Kutsev SI, Polyakov AV. Molecular-Genetic Study of Phenylketonuria in Patients from Georgia. RUSS J GENET+ 2019. [DOI: 10.1134/s1022795419080064] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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16
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Su Y, Wang H, Rejiafu N, Wu B, Jiang H, Chen H, A X, Qian Y, Li M, Lu Y, Ren Y, Li L, Zhou W. The molecular epidemiology of hyperphenylalaninemia in Uygur population: incidence from newborn screening and mutational spectra. ANNALS OF TRANSLATIONAL MEDICINE 2019; 7:258. [PMID: 31355225 DOI: 10.21037/atm.2019.05.16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Background Neonatal hyperphenylalaninemia (HPA) screening did not begin until 2009 in the Uygur population because of poor medical and economic conditions. This study intended to investigate HPA incidence rate and characterize mutation spectrum of phenylalanine hydroxylase (PAH) gene within the Uygur population. Methods Cross-sectional data of National Direct Reporting System database from 2009 to 2016 were used to calculate incidence rate. All HPA positive newborns were diagnosed and confirmed by Sanger sequencing. A low Phe diet was implemented. Results A total of 580,608 Uygur neonates were screened, 111 were diagnosed with HPA with an incidence rate of 1:5,230, 58 different mutations in PAH gene were detected. Eight novel variants were found, including two nonsense mutations (L11*, L197*), two splicing mutations (IVS12-2A > C, IVS13-1G > A), one frameshift mutation (K115 > Hfs) and three missense mutations (E368K, E370G, D435V), distributing in twenty patients. A104D was the most frequent mutation in this study, and the other hot spot of R413P was found in 4 patients in a same Uygur village with a carrier rate of 1:2.1. Conclusions This is the first study to investigate HPA incidence rate in the Uygur population. Our study highlights regional differences in PAH genotypes and mutation rates.
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Affiliation(s)
- Yajie Su
- Department of Neonatology, People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi 830001, China
| | - Huijun Wang
- Shanghai Key Laboratory of Birth Defects, Children's Hospital of Fudan University, Shanghai 201102, China
| | - Nuerya Rejiafu
- Department of Neonatology, People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi 830001, China
| | - Bingbing Wu
- Shanghai Key Laboratory of Birth Defects, Children's Hospital of Fudan University, Shanghai 201102, China.,Key Laboratory of Neonatal Diseases, Ministry of Health, Shanghai 201102, China
| | - Haili Jiang
- Department of Neonatology, People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi 830001, China
| | - Hongbo Chen
- Shanghai Key Laboratory of Birth Defects, Children's Hospital of Fudan University, Shanghai 201102, China
| | - Xian A
- Department of Neonatology, People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi 830001, China
| | - Yanyan Qian
- Shanghai Key Laboratory of Birth Defects, Children's Hospital of Fudan University, Shanghai 201102, China
| | - Mingzhu Li
- Department of Neonatology, People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi 830001, China
| | - Yulan Lu
- Shanghai Key Laboratory of Birth Defects, Children's Hospital of Fudan University, Shanghai 201102, China
| | - Yan Ren
- Department of Neonatology, People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi 830001, China
| | - Long Li
- Department of Neonatology, People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi 830001, China
| | - Wenhao Zhou
- Shanghai Key Laboratory of Birth Defects, Children's Hospital of Fudan University, Shanghai 201102, China.,Key Laboratory of Neonatal Diseases, Ministry of Health, Shanghai 201102, China
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17
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Yan Y, Zhang C, Jin X, Zhang Q, Zheng L, Feng X, Hao S, Gao H, Ma X. Mutation spectrum of PAH gene in phenylketonuria patients in Northwest China: identification of twenty novel variants. Metab Brain Dis 2019; 34:733-745. [PMID: 30747360 DOI: 10.1007/s11011-019-0387-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 01/20/2019] [Indexed: 10/27/2022]
Abstract
This study was performed to analyze the mutational spectrum of the phenylalanine hydroxylase (PAH) gene in phenylketonuria (PKU) patients in Northwest China, to identify mutational hot spots, and to determine the correlation between variants and clinical phenotypes of PKU. A large cohort of 475 PKU families in Northwest China was enrolled to analyze PAH gene variants using Sanger sequencing, Multiplex ligation-dependent probe amplification (MLPA), and gap-PCR. Bioinformatics software was used to predict the pathogenicity of novel variants and analyze the correlations between PAH gene variants and phenotypes of PKU patients. A total of 895 variants were detected in the 950 alleles of 475 patients with PKU (detection rate: 94.21%), 20 of which were novel variants. Other 108, previously known variants, were also identified, with the three most frequent variants being p.Arg243Gln (14.00%), c.611A > G (5.58%), and p.Tyr356* (4.95%). Seven different large deletion/duplication variants were identified by the MLPA method, including the large deletion c.-4163_-406del3758 with high frequency. A correlation analysis between patient phenotype and gene variant frequency showed that p.Arg53His and p.Gln419Arg were correlated with mild hyperphenylalaninemia (MHP). In conclusion, the mutational spectrum underlying PKU in Northwest China was established for the first time. Functional analysis of 20 novel PAH gene variants enriched the PAH gene mutational spectrum. Correlation analysis between variants frequencies in compound heterozygous patients and phenotype severity is helpful for phenotypic prediction.
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Affiliation(s)
- Yousheng Yan
- Graduate School of Peking Union Medical College, Beijing, 100730, China
- National Research Institute for Health and Family Planning, No. 12 Dahuisi Road, Beijing, 100081, China
- Gansu Province Medical Genetics Center, Gansu Province Maternal and Child Health Care Hospital, Lanzhou, 730050, China
| | - Chuan Zhang
- Gansu Province Medical Genetics Center, Gansu Province Maternal and Child Health Care Hospital, Lanzhou, 730050, China
| | - Xiaohua Jin
- Graduate School of Peking Union Medical College, Beijing, 100730, China
- National Research Institute for Health and Family Planning, No. 12 Dahuisi Road, Beijing, 100081, China
| | - Qinhua Zhang
- Gansu Province Medical Genetics Center, Gansu Province Maternal and Child Health Care Hospital, Lanzhou, 730050, China
| | - Lei Zheng
- Gansu Province Medical Genetics Center, Gansu Province Maternal and Child Health Care Hospital, Lanzhou, 730050, China
| | - Xuan Feng
- Gansu Province Medical Genetics Center, Gansu Province Maternal and Child Health Care Hospital, Lanzhou, 730050, China
| | - Shengju Hao
- Gansu Province Medical Genetics Center, Gansu Province Maternal and Child Health Care Hospital, Lanzhou, 730050, China
| | - Huafang Gao
- Graduate School of Peking Union Medical College, Beijing, 100730, China.
- National Research Institute for Health and Family Planning, No. 12 Dahuisi Road, Beijing, 100081, China.
| | - Xu Ma
- Graduate School of Peking Union Medical College, Beijing, 100730, China.
- National Research Institute for Health and Family Planning, No. 12 Dahuisi Road, Beijing, 100081, China.
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Muntau AC, Adams DJ, Bélanger-Quintana A, Bushueva TV, Cerone R, Chien YH, Chiesa A, Coşkun T, de Las Heras J, Feillet F, Katz R, Lagler F, Piazzon F, Rohr F, van Spronsen FJ, Vargas P, Wilcox G, Bhattacharya K. International best practice for the evaluation of responsiveness to sapropterin dihydrochloride in patients with phenylketonuria. Mol Genet Metab 2019; 127:1-11. [PMID: 31103398 DOI: 10.1016/j.ymgme.2019.04.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 03/14/2019] [Accepted: 04/13/2019] [Indexed: 12/26/2022]
Abstract
Phenylketonuria (PKU) is an inherited metabolic disease caused by phenylalanine hydroxylase (PAH) deficiency. As the resulting high blood phenylalanine (Phe) concentration can have detrimental effects on brain development and function, international guidelines recommend lifelong control of blood Phe concentration with dietary and/or medical therapy. Sapropterin dihydrochloride is a synthetic preparation of tetrahydrobiopterin (6R-BH4), the naturally occurring cofactor of PAH. It acts as a pharmacological chaperone, reducing blood Phe concentration and increasing dietary Phe tolerance in BH4-responsive patients with PAH deficiency. Protocols to establish responsiveness to sapropterin dihydrochloride vary widely. Two meetings were held with an international panel of clinical experts in PKU management to develop recommendations for sapropterin dihydrochloride response testing. At the first meeting, regional differences and similarities in testing practices were discussed based on guidelines, a literature review, outcomes of a global physician survey, and case reports. Statements developed based on the discussions were sent to all participants for consensus (>70% of participants) evaluation using a 7-level rating system, and further discussed during the second meeting. The experts recommend sapropterin dihydrochloride response testing in patients with untreated blood Phe concentrations of 360-2000 μmol/L, except in those with two null mutations. For neonates, a 24-h sapropterin dihydrochloride loading test is recommended; responsiveness is defined as a decrease in blood Phe ≥30%. For older infants, children, adolescents, and adults, a test duration of ≥48 h or a 4-week trial is recommended. The main endpoint for a 48-h to 7-day trial is a decrease in blood Phe, while improved Phe tolerance is the endpoint to be assessed during a longer trial. Longer trials may not be feasible in some locations due to lack of reimbursement for hospitalization, while a 4-week trial may not be possible due to limited access to sapropterin dihydrochloride or public health regulation. A 48-h response test should be considered in pregnant patients who cannot achieve blood Phe ≤360 μmol/L with a Phe-restricted diet. Durability of response and clinical benefits of sapropterin dihydrochloride should be assessed over the long term. Harmonization of protocols is expected to improve identification of responders and comparability of test results worldwide.
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Affiliation(s)
- Ania C Muntau
- University Children's Hospital, University Medical Center Hamburg Eppendorf, Hamburg, Germany.
| | - Darius J Adams
- Atlantic Health System, Morristown Medical Center, Morristown, NJ, USA.
| | | | - Tatiana V Bushueva
- National Medical Research Center of Children's Health of the Ministry of Health of the Russian Federation, Moscow, Russia.
| | - Roberto Cerone
- G. Gaslini Institute, University of Genova, Genova, Italy.
| | | | - Ana Chiesa
- Centro de Investigaciones Endocrinologicas "Dr Cesar Bergadá" CEDIE, CONICET, Hospital de Niños Ricardo Gutierrez, Fundacion de Endocrinologia Infantil, Buenos Aires, Argentina.
| | - Turgay Coşkun
- Hacettepe University Faculty of Medicine, Ankara, Turkey.
| | - Javier de Las Heras
- Hospital Universitario de Cruces, Biocruces Health Research Institute and University of the Basque Country UPV/EHU, Vizcaya, Spain.
| | - François Feillet
- Children's University Hospital, CHU Brabois, Vandoeuvre les Nancy, France.
| | - Rachel Katz
- Ann and Robert Lurie Children's Hospital of Chicago, Chicago, IL, USA.
| | | | - Flavia Piazzon
- Associação de Pais e Amigos dos Excepcionais de São Paulo (APAE DE SÃO PAULO), São Paulo, SP, Brazil.
| | - Fran Rohr
- Boston Children's Hospital, Boston, MA, USA.
| | - Francjan J van Spronsen
- Beatrix Children's Hospital, University Medical Center of Groningen, University of Groningen, Groningen, the Netherlands.
| | - Paula Vargas
- Hospital Materno Infantil Presidente Vargas, Porto Alegre, RS, Brazil.
| | - Gisela Wilcox
- University of Manchester & Salford Royal NHS Foundation Trust, Salford, UK.
| | - Kaustuv Bhattacharya
- Genetic Metabolic Disorders Service, University of Sydney, Children's Hospital Westmead Clinical School, Sydney, NSW, Australia.
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Genotypes of 2579 patients with phenylketonuria reveal a high rate of BH4 non-responders in Russia. PLoS One 2019; 14:e0211048. [PMID: 30668579 PMCID: PMC6342299 DOI: 10.1371/journal.pone.0211048] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 12/30/2018] [Indexed: 12/12/2022] Open
Abstract
Phenylalanine hydroxylase (PAH) deficiency is responsible for most cases of phenylketonuria (PKU). Furthermore, numerous studies on BH4-sensitive PAH deficiency have been conducted. To date, BH4, a cofactor of PAH, has not been used to treat PKU in Russia.Genotype data of patients with PKU can be used to predict their sensitivity to BH4 therapy. A cohort of 2579 patients with PKU from Russia was analyzed for 25 common PAH gene mutations using custom allele-specific multiplex ligation-dependent probe amplification-based technology. A mutation detection rate of 84.1% chromosomes was accomplished. Both pathogenic alleles were identified in 73.1% of patients. The most frequent pathogenic variants were p.Arg408Trp (50.9%), p.Arg261Gln (5.3%), p.Pro281Leu (3.5%), IVS12+1G>A (3.1%), IVS10-11G>A (2.6%), and p.Arg158Leu (2.4%). The exact boundaries of a PAH exon 5 deletion were defined as EX5del4154ins268 (c.442-2913_509+1173del4154ins268). Severe phenotypes prevailed in the cohort, and classical PKU was observed in 71.8% cases. Due to the genotype-based prediction, 55.9% of the probands were non-responders to the BH4-treatment, and 20.2% were potential responders. Analysis of genotype data is useful to predict BH4 response in PKU patients. The high rate of non-responders among Russian patients was due to the high allele frequency of severe PAH mutations.
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Garbade SF, Shen N, Himmelreich N, Haas D, Trefz FK, Hoffmann GF, Burgard P, Blau N. Allelic phenotype values: a model for genotype-based phenotype prediction in phenylketonuria. Genet Med 2018; 21:580-590. [DOI: 10.1038/s41436-018-0081-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Accepted: 05/31/2018] [Indexed: 02/08/2023] Open
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Wasim M, Awan FR, Khan HN, Tawab A, Iqbal M, Ayesha H. Aminoacidopathies: Prevalence, Etiology, Screening, and Treatment Options. Biochem Genet 2017; 56:7-21. [PMID: 29094226 DOI: 10.1007/s10528-017-9825-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 09/18/2017] [Indexed: 12/26/2022]
Abstract
Inborn errors of metabolism (IEMs) are a group of inherited metabolic disorders which are caused by mutations in the specific genes that lead to impaired proteins or enzymes production. Different metabolic pathways are perturbed due to the deficiency or lack of enzymes. To date, more than 500 IEMs have been reported with most of them being untreatable. However, fortunately 91 such disorders are potentially treatable, if diagnosed at an earlier stage of life. IEMs have been classified into different categories and one class of IEMs, characterized by the physiological disturbances of amino acids is called as aminoacidopathies. Out of 91 treatable IEM, thirteen disorders are amino acid related. Aminoacidopathies can be detected by chromatography and mass spectrometry based analytical techniques (e.g., HPLC, GC-MS, LC-MS/MS) for amino acid level changes, and through genetic assays (e.g., PCR, TaqMan Genotyping, DNA sequencing) at the mutation level in the corresponding genes. Hence, this review is focused to describe thirteen common aminoacidopathies namely: Phenylketonuria (PKU), Maple Syrup Urine Disease (MSUD), Homocystinuria/Methylene Tetrahydrofolate Reductase (MTHFR) deficiency, Tyrosinemia type II, Citrullinemia type I and type II, Argininosuccinic aciduria, Carbamoyl Phosphate Synthetase I (CPS) deficiency, Argininemia (arginase deficiency), Hyperornithinemia-Hyperammonemia-Homocitrullinuria (HHH) syndrome, N-Acetylglutamate Synthase (NAGS) deficiency, Ornithine Transcarbamylase (OTC) deficiency, and Pyruvate Dehydrogenase (PDH) complex deficiency. Furthermore, the etiology, prevalence and commonly used analytical techniques for screening of aminoacidopathies are briefly described. This information would be helpful to researchers and clinicians especially from developing countries to initiate newborn screening programs for aminoacidopathies.
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Affiliation(s)
- Muhammad Wasim
- Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE) / [Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad], Jhang Road, P.O. Box. 577, Faisalabad, 38000, Pakistan
| | - Fazli Rabbi Awan
- Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE) / [Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad], Jhang Road, P.O. Box. 577, Faisalabad, 38000, Pakistan.
| | - Haq Nawaz Khan
- Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE) / [Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad], Jhang Road, P.O. Box. 577, Faisalabad, 38000, Pakistan
| | - Abdul Tawab
- Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE) / [Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad], Jhang Road, P.O. Box. 577, Faisalabad, 38000, Pakistan
| | - Mazhar Iqbal
- Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE) / [Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad], Jhang Road, P.O. Box. 577, Faisalabad, 38000, Pakistan
| | - Hina Ayesha
- DHQ Hospital, Faisalabad Medical University, Faisalabad, Pakistan
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22
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Liu N, Huang Q, Li Q, Zhao D, Li X, Cui L, Bai Y, Feng Y, Kong X. Spectrum of PAH gene variants among a population of Han Chinese patients with phenylketonuria from northern China. BMC MEDICAL GENETICS 2017; 18:108. [PMID: 28982351 PMCID: PMC5629770 DOI: 10.1186/s12881-017-0467-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 09/27/2017] [Indexed: 12/14/2022]
Abstract
Background Phenylketonuria (PKU), which primarily results from a deficiency of phenylalanine hydroxylase (PAH), is one of the most common inherited inborn errors of metabolism that impairs postnatal cognitive development. The incidence of various PAH variations differs by race and ethnicity. The aim of the present study was to characterize the PAH gene variants of a Han population from Northern China. Methods In total, 655 PKU patients and their families were recruited for this study; each proband was diagnosed both clinically and biochemically with phenylketonuria. Subjects were sequentially screened for single-base variants and exon deletions or duplications within PAH via direct Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA). Results A spectrum of 174 distinct PAH variants was identified: 152 previously documented variants and 22 novel variants. While single-base variants were distributed throughout the 13 exons, they were particularly concentrated in exons 7 (33.3%), 11 (14.2%), 6 (13.2%), 12 (11.0%), 3 (10.4%), and 5 (4.4%). The predominant variant was p.Arg243Gln (17.7%), followed by Ex6-96A > G (8.3%), p.Val399 = (6.4%), p.Arg53His (4.7%), p.Tyr356* (4.7%), p.Arg241Cys (4.6%), p.Arg413Pro (4.6%), p.Arg111* (4.4%), and c.442-1G > A (3.4%). Notably, two patients were also identified as carrying de novo variants. Conclusion The composition of PAH gene variants in this Han population from Northern China was distinct from those of other ethnic groups. As such, the construction of a PAH gene variant database for Northern China is necessary to lay a foundation for genetic-based diagnoses, prenatal diagnoses, and population screening. Electronic supplementary material The online version of this article (10.1186/s12881-017-0467-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ning Liu
- Genetics and Prenatal Diagnosis Center, The First Affiliated Hospital of Zhengzhou University, Henan Engineering Research Center for Gene Editing of Human Genetic Disease, Jianshe Rd, Erqi District, Zhengzhou, Henan, 450052, People's Republic of China
| | - Qiuying Huang
- State Key Laboratory of Cellular Stress Biology, State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, Engineering Research Centre of Molecular Diagnostics, Ministry of Education, School of Life Sciences, Xiamen University, Xiangan Rd, Xiangan District, Xiamen, Fujian, 361102, People's Republic of China
| | - Qingge Li
- State Key Laboratory of Cellular Stress Biology, State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, Engineering Research Centre of Molecular Diagnostics, Ministry of Education, School of Life Sciences, Xiamen University, Xiangan Rd, Xiangan District, Xiamen, Fujian, 361102, People's Republic of China
| | - Dehua Zhao
- Neonatal Screening Center, The Third Affiliated Hospital of Zhengzhou University, Kangfu Rd, Erqi District, Zhengzhou, Henan, 450052, People's Republic of China
| | - Xiaole Li
- Neonatal Screening Center, The Third Affiliated Hospital of Zhengzhou University, Kangfu Rd, Erqi District, Zhengzhou, Henan, 450052, People's Republic of China
| | - Lixia Cui
- Neonatal Screening Center, Zhengzhou Maternity and Child Care Hospital, Jinshui Rd, Jinshui District, Zhengzhou, Henan, 450012, People's Republic of China
| | - Ying Bai
- Genetics and Prenatal Diagnosis Center, The First Affiliated Hospital of Zhengzhou University, Henan Engineering Research Center for Gene Editing of Human Genetic Disease, Jianshe Rd, Erqi District, Zhengzhou, Henan, 450052, People's Republic of China
| | - Yin Feng
- Genetics and Prenatal Diagnosis Center, The First Affiliated Hospital of Zhengzhou University, Henan Engineering Research Center for Gene Editing of Human Genetic Disease, Jianshe Rd, Erqi District, Zhengzhou, Henan, 450052, People's Republic of China
| | - Xiangdong Kong
- Genetics and Prenatal Diagnosis Center, The First Affiliated Hospital of Zhengzhou University, Henan Engineering Research Center for Gene Editing of Human Genetic Disease, Jianshe Rd, Erqi District, Zhengzhou, Henan, 450052, People's Republic of China.
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23
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Gundorova P, Stepanova AA, Bushueva TV, Belyashova EY, Zinchenko RA, Amelina SS, Kutsev SI, Polyakov AV. Genotyping of patients with phenylketonuria from different regions of Russia for determining BH4 responsiveness. RUSS J GENET+ 2017. [DOI: 10.1134/s1022795417060060] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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24
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Shen N, Heintz C, Thiel C, Okun JG, Hoffmann GF, Blau N. Co-expression of phenylalanine hydroxylase variants and effects of interallelic complementation on in vitro enzyme activity and genotype-phenotype correlation. Mol Genet Metab 2016; 117:328-35. [PMID: 26803807 DOI: 10.1016/j.ymgme.2016.01.004] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 01/09/2016] [Indexed: 02/04/2023]
Abstract
BACKGROUND In phenylketonuria (PKU) patients, the combination of two phenylalanine hydroxylase (PAH) alleles is the main determinant of residual enzyme activity in vivo and in vitro. Inconsistencies in genotype-phenotype correlations have been observed in compound heterozygous patients and a particular combination of two PAH alleles may produce a phenotype that is different from the expected one, possibly due to interallelic complementation. METHODS A dual eukaryotic vector system with two distinct PAH proteins N-terminally fused to different epitope tags was used to investigate the co-expression of PAH alleles reported in patients with inconsistent phenotypes. PAH variant proteins were transiently co-transfected in COS-7 cells. PAH activity was measured by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS), and protein expression was measured by Western blot. Genotypes were compared with predicted PAH activity from the PAH locus-specific database (PAHvdb) and with phenotypes and tetrahydrobiopterin (BH4) responsiveness from more than 10,000 PKU patients (BIOPKU database). RESULTS Through the expression and co-expression of 17 variant alleles we demonstrated that interallelic interaction could be both positive and negative. The co-expressions of p.[I65T];[R261Q] (19.5% activity; predicted 43.5%) and p.[I65T];[R408W] (15.0% vs. 26.8% activity) are examples of genotypes with negative interallelic interaction. The co-expressions of p.[E178G];[Q232E] (55.0% vs.36.4%) and p.[P384S];[R408W] (56.1% vs. 40.8%) are examples of positive subunit interactions. Inconsistencies of PAH residual enzyme activity in vitro and of PKU patients' phenotypes were observed as well. The PAH activity of p.[R408W];[A300S] is 18.0% of the wild-type activity; however, 88% of patients with this genotype exhibit mild hyperphenylalaninemias (MHPs). CONCLUSION The co-expression of two distinct PAH variants revealed possible dominance effects (positive or negative) by one of the variants on residual PAH activity as a result of interallelic complementation.
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Affiliation(s)
- Nan Shen
- Dietmar-Hopp Metabolic Center, University Children's Hospital, Department of General Pediatrics, Heidelberg, Germany
| | - Caroline Heintz
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, MA, United States
| | - Christian Thiel
- Dietmar-Hopp Metabolic Center, University Children's Hospital, Department of General Pediatrics, Heidelberg, Germany
| | - Jürgen G Okun
- Dietmar-Hopp Metabolic Center, University Children's Hospital, Department of General Pediatrics, Heidelberg, Germany
| | - Georg F Hoffmann
- Dietmar-Hopp Metabolic Center, University Children's Hospital, Department of General Pediatrics, Heidelberg, Germany
| | - Nenad Blau
- Dietmar-Hopp Metabolic Center, University Children's Hospital, Department of General Pediatrics, Heidelberg, Germany.
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25
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Jeannesson-Thivisol E, Feillet F, Chéry C, Perrin P, Battaglia-Hsu SF, Herbeth B, Cano A, Barth M, Fouilhoux A, Mention K, Labarthe F, Arnoux JB, Maillot F, Lenaerts C, Dumesnil C, Wagner K, Terral D, Broué P, de Parscau L, Gay C, Kuster A, Bédu A, Besson G, Lamireau D, Odent S, Masurel A, Guéant JL, Namour F. Genotype-phenotype associations in French patients with phenylketonuria and importance of genotype for full assessment of tetrahydrobiopterin responsiveness. Orphanet J Rare Dis 2015; 10:158. [PMID: 26666653 PMCID: PMC5024853 DOI: 10.1186/s13023-015-0375-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 12/08/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Mutations in Phenylalanine Hydroxylase (PAH) gene cause phenylketonuria. Sapropterin (BH4), the enzyme cofactor, is an important therapeutical strategy in phenylketonuria. However, PAH is a highly polymorphic gene and it is difficult to identify BH4-responsive genotypes. We seek here to improve prediction of BH4-responsiveness through comparison of genotypes, BH4-loading test, predictions of responsiveness according to the literature and types and locations of mutations. METHODS A total of 364 French patients among which, 9 % had mild hyperphenylalaninemia, 17.7 % mild phenylketonuria and 73.1 % classical phenylketonuria, benefited from a 24-hour BH4-loading test and had the PAH gene sequenced and analyzed by Multiplex Ligation Probe Amplification. RESULTS Overall, 31.6 % of patients were BH4-responsive. The number of different mutations found was 127, including 26 new mutations. The mutations c.434A > T, c.500A > T, c.529G > C, c.1045 T > G and c.1196 T > C were newly classified as being BH4-responsive. We identified 261 genotypes, among which 46 were newly recognized as being BH4-responsive. Even though patients carry 2 responsive alleles, BH4-responsiveness cannot be predicted with certainty unless they present mild hyperphenylalaninemia. BH4-responsiveness cannot be predicted in patients carrying one responsive mutation only. In general, the milder the phenotype is, the stronger the BH4-response is. Almost exclusively missense mutations, particularly in exons 12, 11 and 8, are associated with BH4-responsiveness and any other type of mutation predicts a negative response. CONCLUSIONS This study is the first of its kind, in a French population, to identify the phenotype associated with several combinations of PAH mutations. As others, it highlights the necessity of performing simultaneously BH4 loading test and molecular analysis in monitoring phenylketonuria patients.
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Affiliation(s)
- Elise Jeannesson-Thivisol
- Reference Center for Inherited Metabolic Diseases, University Hospital of Nancy, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France
- INSERM U954, Department of Nutrition-Genetics-Environmental Risk Exposure, University of Lorraine, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France
| | - François Feillet
- Reference Center for Inherited Metabolic Diseases, University Hospital of Nancy, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France
- INSERM U954, Department of Nutrition-Genetics-Environmental Risk Exposure, University of Lorraine, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France
| | - Céline Chéry
- Reference Center for Inherited Metabolic Diseases, University Hospital of Nancy, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France
- INSERM U954, Department of Nutrition-Genetics-Environmental Risk Exposure, University of Lorraine, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France
| | - Pascal Perrin
- Reference Center for Inherited Metabolic Diseases, University Hospital of Nancy, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France
- INSERM U954, Department of Nutrition-Genetics-Environmental Risk Exposure, University of Lorraine, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France
| | - Shyue-Fang Battaglia-Hsu
- Reference Center for Inherited Metabolic Diseases, University Hospital of Nancy, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France
- INSERM U954, Department of Nutrition-Genetics-Environmental Risk Exposure, University of Lorraine, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France
| | - Bernard Herbeth
- Reference Center for Inherited Metabolic Diseases, University Hospital of Nancy, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France
- INSERM U954, Department of Nutrition-Genetics-Environmental Risk Exposure, University of Lorraine, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France
| | - Aline Cano
- Reference Center for Inherited Metabolic Diseases, Timone Hospital, Marseille, France
| | - Magalie Barth
- Department of Biochemistry and Genetics, Angers University Hospital, Angers, France
| | - Alain Fouilhoux
- Reference Center for Inherited Metabolic Diseases, Hospices Civils de Lyon, Bron, France
| | - Karine Mention
- Reference Center for Inherited Metabolic Diseases, Jeanne de Flandres Hospital, Lille, France
| | - François Labarthe
- Department of Pediatric Medicine, Clocheville Hospital, Tours, France
| | - Jean-Baptiste Arnoux
- Reference Center for Inherited Metabolic Diseases, Necker-Enfants Malades Hospital, Paris, France
| | - François Maillot
- Department of Internal Medicine, Tours University Hospital, Tours, France
| | | | - Cécile Dumesnil
- Pediatric Hematology and Oncology, Rouen University-Hospital, Rouen, France
| | - Kathy Wagner
- Department of Pediatrics, Lenval Hospital, Nice, France
| | - Daniel Terral
- Department of Pediatrics, Hotel-Dieu Hospital, Clermont-Ferrand, France
| | - Pierre Broué
- Department of Pediatric Hepatology and Metabolic Diseases, Children Hospital, Toulouse, France
| | | | - Claire Gay
- Department of Pediatrics, Saint-Etienne University-Hospital, Saint-Etienne, France
| | - Alice Kuster
- Pediatric Department, Nantes University Hospital, Nantes, France
| | - Antoine Bédu
- Neonatology Department, Mère-Enfant Hospital, Limoges, France
| | - Gérard Besson
- Department of Neurology, University Hospital of Grenoble, Grenoble, France
| | - Delphine Lamireau
- Department of Pediatrics, Pellegrin-Enfants Hospital, Bordeaux, France
| | - Sylvie Odent
- Department of Clinical Genetics, Rennes University Hospital, Rennes, France
| | - Alice Masurel
- Department of Medical Genetics, Dijon University-Hospital, Dijon, France
| | - Jean-Louis Guéant
- Reference Center for Inherited Metabolic Diseases, University Hospital of Nancy, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France
- INSERM U954, Department of Nutrition-Genetics-Environmental Risk Exposure, University of Lorraine, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France
| | - Fares Namour
- Reference Center for Inherited Metabolic Diseases, University Hospital of Nancy, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France.
- INSERM U954, Department of Nutrition-Genetics-Environmental Risk Exposure, University of Lorraine, 9 ave Forêt de Haye, BP 184, 54511, Vandoeuvre-lès-Nancy, France.
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Bayat A, Yasmeen S, Lund A, Nielsen JB, Møller LB. Mutational and phenotypical spectrum of phenylalanine hydroxylase deficiency in Denmark. Clin Genet 2015; 90:247-51. [PMID: 26542770 DOI: 10.1111/cge.12692] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Revised: 10/16/2015] [Accepted: 11/03/2015] [Indexed: 11/30/2022]
Abstract
We describe the genotypes of the complete cohort, from 1967 to 2014, of phenylketonuria (PKU) patients in Denmark, in total 376 patients. A total of 752 independent alleles were investigated. Mutations were identified on 744 PKU alleles (98.9%). In total, 82 different mutations were present in the cohort. The most frequent mutation c.1315+1G>A (IVS12+1G>A) was found on 25.80% of the 744 alleles. Other very frequent mutations were c.1222C>T (p.R408W) (16.93%) and c.1241A>G (p.Y414C) (11.15%). Among the identified mutations, five mutations; c.532G>A (p.E178K), c.730C>T (p.P244S), c.925G>A (p.A309T), c.1228T>A (p.F410I), and c.1199+4A>G (IVS11+4A>G) have not been reported previously. The metabolic phenotypes of PKU are classified into four categories; 'classical PKU', 'moderate PKU', 'mild PKU' and 'mild hyperphenylalaninemia'. In this study, we assigned the phenotypic outcome of three of the five novel mutations and furthermore six not previously classified mutations to one of the four PKU categories.
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Affiliation(s)
- A Bayat
- Clinical Genetic Clinic, Kennedy Center, Copenhagen University Hospital, Glostrup, Denmark.,Department of Pediatrics Hvidovre Hospital Kettegård Alle 30, 2650 Hvidovre, Denmark
| | - S Yasmeen
- Clinical Genetic Clinic, Kennedy Center, Copenhagen University Hospital, Glostrup, Denmark
| | - A Lund
- Clinical Genetic Clinic, Centre for Inherited Metabolic Diseases, Copenhagen University Hospital, Copenhagen, Denmark
| | - J B Nielsen
- Clinical Genetic Clinic, Kennedy Center, Copenhagen University Hospital, Glostrup, Denmark
| | - L B Møller
- Department of Science, Systems and Models (NSM), Roskilde University, DK 4000 Roskilde, Denmark
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27
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Tao J, Li N, Jia H, Liu Z, Li X, Song J, Deng Y, Jin X, Zhu J. Correlation between genotype and the tetrahydrobiopterin-responsive phenotype in Chinese patients with phenylketonuria. Pediatr Res 2015; 78:691-9. [PMID: 26322415 PMCID: PMC4700046 DOI: 10.1038/pr.2015.167] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2015] [Accepted: 06/17/2015] [Indexed: 01/30/2023]
Abstract
BACKGROUND A growing body of research has suggested that tetrahydrobiopterin (BH4) responsive phenotype can be predicted by the phenylalanine hydroxylase (PAH) genotype in patients with phenylketonuria (PKU), but data concerning the association between genotype and BH4 responsiveness are scarce in China. METHODS A total of 165 PKU patients from China who had undergone a 24-h loading test with BH4 administration were recruited. Genotyping was performed by the next-generation sequencing (NGS) technique. Using the predicted residual PAH activity, we analyzed the association between genotype and BH4-responsiveness. RESULTS Among the 165 patients, 40 patients (24.24%) responded to BH4. A total of 74 distinct mutations were observed, including 13 novel mutations. The mutation p.R241C was most frequently associated with response. Two known mutations (p.A322T and p.Q419R) and two novel mutations (p.L98V and IVS3-2A>T) were first reported as responsive to BH4. Residual PAH activity of at least 12.5% was needed for responsive genotypes. CONCLUSION Genotype-based predictions of BH4-responsiveness are only for selecting potential responders. Accordingly, it is necessary to test potential responders with a long-term BH4 challenge.
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Affiliation(s)
- Jing Tao
- National Centre for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sichuan, China
- West China School of Public Health, Sichuan University, Sichuan, China
| | - Nana Li
- National Centre for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sichuan, China
- Laboratory of Molecular Epidemiology for Birth Defects, West China Second University Hospital, Sichuan University, Sichuan, China
| | - Haitao Jia
- BGI-Shenzhen, Shenzhen, Guangdong, China
| | - Zhen Liu
- National Centre for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sichuan, China
- Laboratory of Molecular Epidemiology for Birth Defects, West China Second University Hospital, Sichuan University, Sichuan, China
| | - Xiaohong Li
- National Centre for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sichuan, China
- Laboratory of Molecular Epidemiology for Birth Defects, West China Second University Hospital, Sichuan University, Sichuan, China
| | | | - Ying Deng
- National Centre for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sichuan, China
- Laboratory of Molecular Epidemiology for Birth Defects, West China Second University Hospital, Sichuan University, Sichuan, China
| | - Xi Jin
- National Centre for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sichuan, China
- Laboratory of Molecular Epidemiology for Birth Defects, West China Second University Hospital, Sichuan University, Sichuan, China
| | - Jun Zhu
- National Centre for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sichuan, China
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28
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Li N, Jia H, Liu Z, Tao J, Chen S, Li X, Deng Y, Jin X, Song J, Zhang L, Liang Y, Wang W, Zhu J. Molecular characterisation of phenylketonuria in a Chinese mainland population using next-generation sequencing. Sci Rep 2015; 5:15769. [PMID: 26503515 PMCID: PMC4621502 DOI: 10.1038/srep15769] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 10/01/2015] [Indexed: 11/28/2022] Open
Abstract
Phenylketonuria (PKU) is an inherited autosomal recessive disorder of phenylalanine metabolism, mainly caused by a deficiency of phenylalanine hydroxylase (PAH). The incidence of various PAH mutations differs among race and ethnicity. Here we report a spectrum of PAH mutations complied from 796 PKU patients from mainland China. The all 13 exons and adjacent intronic regions of the PAH gene were determined by next-generation sequencing. We identified 194 different mutations, of which 41 are not reported before. Several mutations reoccurred with high frequency including p.R243Q, p.EX6-96A > G, p.V399V, p.R241C, p.R111*, p.Y356*, p.R413P, and IVS4-1G > A. 76.33% of mutations were localized in exons 3, 6, 7, 11, 12. We further compared the frequency of each mutation between populations in northern and southern China, and found significant differences in 19 mutations. Furthermore, we identified 101 mutations that are not reported before in Chinese population, our study thus broadens the mutational spectrum of Chinese PKU patients. Additionally, 41 novel mutations will expand and improve PAH mutation database. Finally, our study offers proof that NGS is effective, reduces screening times and costs, and facilitates the provision of appropriate genetic counseling for PKU patients.
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Affiliation(s)
- Nana Li
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec. 3 No. 20, South RenMin Road, Chengdu, Sichuan, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, West China Second University Hospital, Sichuan University, Sec. 3 No. 20, South RenMin Road, Chengdu, Sichuan, China
| | - Haitao Jia
- BGI-Shenzhen, Building No. 11, Beishan Industrial Zone, Yantian District, Shenzhen, Guangdong China
| | - Zhen Liu
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec. 3 No. 20, South RenMin Road, Chengdu, Sichuan, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, West China Second University Hospital, Sichuan University, Sec. 3 No. 20, South RenMin Road, Chengdu, Sichuan, China
| | - Jing Tao
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec. 3 No. 20, South RenMin Road, Chengdu, Sichuan, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, West China Second University Hospital, Sichuan University, Sec. 3 No. 20, South RenMin Road, Chengdu, Sichuan, China
| | - Song Chen
- BGI-Shenzhen, Building No. 11, Beishan Industrial Zone, Yantian District, Shenzhen, Guangdong China
| | - Xiaohong Li
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec. 3 No. 20, South RenMin Road, Chengdu, Sichuan, China.,Laboratory of Molecular Epidemiology for birth defect, West China Institute of Women and Children's Health, Sichuan University, Chengdu, China
| | - Ying Deng
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec. 3 No. 20, South RenMin Road, Chengdu, Sichuan, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, West China Second University Hospital, Sichuan University, Sec. 3 No. 20, South RenMin Road, Chengdu, Sichuan, China
| | - Xi Jin
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec. 3 No. 20, South RenMin Road, Chengdu, Sichuan, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, West China Second University Hospital, Sichuan University, Sec. 3 No. 20, South RenMin Road, Chengdu, Sichuan, China
| | - Jiaping Song
- BGI-Shenzhen, Building No. 11, Beishan Industrial Zone, Yantian District, Shenzhen, Guangdong China
| | - Liangtao Zhang
- BGI-Shenzhen, Building No. 11, Beishan Industrial Zone, Yantian District, Shenzhen, Guangdong China
| | - Yu Liang
- BGI-Shenzhen, Building No. 11, Beishan Industrial Zone, Yantian District, Shenzhen, Guangdong China
| | - Wei Wang
- BGI-Shenzhen, Building No. 11, Beishan Industrial Zone, Yantian District, Shenzhen, Guangdong China
| | - Jun Zhu
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec. 3 No. 20, South RenMin Road, Chengdu, Sichuan, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, West China Second University Hospital, Sichuan University, Sec. 3 No. 20, South RenMin Road, Chengdu, Sichuan, China.,Laboratory of Molecular Epidemiology for birth defect, West China Institute of Women and Children's Health, Sichuan University, Chengdu, China
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29
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Trunzo R, Santacroce R, D'Andrea G, Longo V, De Girolamo G, Dimatteo C, Leccese A, Bafunno V, Lillo V, Papadia F, Margaglione M. Phenylalanine hydroxylase deficiency in south Italy: Genotype-phenotype correlations, identification of a novel mutant PAH allele and prediction of BH4 responsiveness. Clin Chim Acta 2015; 450:51-5. [PMID: 26210745 DOI: 10.1016/j.cca.2015.07.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 07/13/2015] [Accepted: 07/14/2015] [Indexed: 10/23/2022]
Abstract
We investigated the mutation spectrum of the phenylalanine hydroxylase gene (PAH) in a cohort of patients from 33 Italian PKU families. Mutational screening of the known coding region, including conventional intron splice sites, was performed by direct sequencing of the patients' genomic DNA. Thirty-three different disease causing mutations were identified in our patient group, including 19 missense, 6 splicing, 3 nonsense, 5 deletions, with a detection rate of 100%. The most prevalent mutation was the IVS10-11G>A, accounting for 12.1% of PKU alleles studied. Other frequent mutations were: p.R261Q (9.1%), p.P281L (7.6%), and p.R408W (6.1%). We also identified one novel missense mutation, p.H290Q. A spectrum of 31 different genotypes was observed and a genotype based predictions of BH4-responsiveness were assessed. Among all genotypes, 13 were predicted to be BH4-responsive represented by thirteen PKU families. In addition, genotype-phenotype correlations were performed. This study reveals the importance of a full genotyping of PKU patients and the prediction of BH4-responsiveness, not only because of the definitive diagnosis and prediction of the optimal diet, but also to point out those patients that could benefit from new therapeutic approach. They may potentially benefit from BH4 therapy which, combined with a less strict diet, or eventually in special cases as monotherapy, may contribute to reduce nutritional deficiencies and minimize neurological and psychological dysfunctions.
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Affiliation(s)
- Roberta Trunzo
- Genetica Medica, Dipartimento di Medicina Clinica e Sperimentale, Università degli Studi di Foggia, Italy.
| | - Rosa Santacroce
- Genetica Medica, Dipartimento di Medicina Clinica e Sperimentale, Università degli Studi di Foggia, Italy
| | - Giovanna D'Andrea
- Genetica Medica, Dipartimento di Medicina Clinica e Sperimentale, Università degli Studi di Foggia, Italy
| | - Vittoria Longo
- Genetica Medica, Dipartimento di Medicina Clinica e Sperimentale, Università degli Studi di Foggia, Italy
| | - Giuseppe De Girolamo
- Genetica Medica, Dipartimento di Medicina Clinica e Sperimentale, Università degli Studi di Foggia, Italy
| | - Claudia Dimatteo
- Genetica Medica, Dipartimento di Medicina Clinica e Sperimentale, Università degli Studi di Foggia, Italy
| | - Angelica Leccese
- Genetica Medica, Dipartimento di Medicina Clinica e Sperimentale, Università degli Studi di Foggia, Italy
| | - Valeria Bafunno
- Genetica Medica, Dipartimento di Medicina Clinica e Sperimentale, Università degli Studi di Foggia, Italy
| | | | | | - Maurizio Margaglione
- Genetica Medica, Dipartimento di Medicina Clinica e Sperimentale, Università degli Studi di Foggia, Italy
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Gemperle-Britschgi C, Iorgulescu D, Mager MA, Anton-Paduraru D, Vulturar R, Thöny B. A novel common large genomic deletion and two new missense mutations identified in the Romanian phenylketonuria population. Gene 2015; 576:182-8. [PMID: 26481238 DOI: 10.1016/j.gene.2015.10.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Revised: 06/02/2015] [Accepted: 10/12/2015] [Indexed: 10/22/2022]
Abstract
The mutation spectrum for the phenylalanine hydroxylase (PAH) gene was investigated in a cohort of 84 hyperphenylalaninemia (HPA) patients from Romania identified through newborn screening or neurometabolic investigations. Differential diagnosis identified 81 patients with classic PAH deficiency while 3 had tetrahydropterin-cofactor deficiency and/or remained uncertain due to insufficient specimen. PAH-genetic analysis included a combination of Sanger sequencing of exons and exon–intron boundaries, MLPA and NGS with genomic DNA, and cDNA analysis from immortalized lymphoblasts. A diagnostic efficiency of 99.4% was achieved, as for one allele (out of a total of 162 alleles) no mutation could be identified. The most prevalent mutation was p.Arg408Trp which was found in ~ 38% of all PKU alleles. Three novel mutations were identified, including the two missense mutations p.Gln226Lys and p.Tyr268Cys that were both disease causing by prediction algorithms, and the large genomic deletion EX6del7831 (c.509 + 4140_706 + 510del7831) that resulted in skipping of exon 6 based on PAH-cDNA analysis in immortalized lymphocytes. The genomic deletion was present in a heterozygous state in 12 patients, i.e. in ~ 8% of all the analyzed PKU alleles, and might have originated from a Romanian founder.
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Affiliation(s)
- Corinne Gemperle-Britschgi
- Division of Clinical Chemistry and Biochemistry, Department of Pediatrics, University of Zürich, Zürich, Switzerland
| | - Daniela Iorgulescu
- Center of Newborn Screening, Department of Pediatrics, Institute for Mother and Child Care, Bucharest, 120 Lacul Tei Blv., 020395, Romania
| | - Monica Alina Mager
- "I. Hatieganu" University of Medicine and Pharmacy - Cluj-Napoca, Department of Neurology, Romania
| | - Dana Anton-Paduraru
- "Gr.T.Popa" University of Medicine and Pharmacy, Newborn Screening Center Iasi, 3rd Clinic of Pediatrics, Romania
| | - Romana Vulturar
- "I.Hatieganu" University of Medicine and Pharmacy - Cluj-Napoca, Department of Molecular Sciences, Cluj-Napoca, Romania; Cognitive Neuroscience Laboratory, Babes-Bolyai University - Cluj-Napoca, Romania.
| | - Beat Thöny
- Division of Clinical Chemistry and Biochemistry, Department of Pediatrics, University of Zürich, Zürich, Switzerland; Division of Metabolism, Department of Pediatrics, University of Zurich, Steinwiesstrasse 75, Zurich CH-8032, Switzerland; Neuroscience Centre Zürich, University of Zürich, Zürich, Switzerland; Neuroscience Centre Zürich, ETH Zürich (ZNZ), Zürich, Switzerland; Children's Research Centre (CRC), Zürich, Switzerland.
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31
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Pimentel FB, Alves RC, Oliva-Teles MT, Costa ASG, Fernandes TJR, Almeida MF, Torres D, Delerue-Matos C, Oliveira MBPP. Targeting specific nutrient deficiencies in protein-restricted diets: some practical facts in PKU dietary management. Food Funct 2015; 5:3151-9. [PMID: 25277724 DOI: 10.1039/c4fo00555d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Among aminoacidopathies, phenylketonuria (PKU) is the most prevalent one. Early diagnosis in the neonatal period with a prompt nutritional therapy (low natural-protein and phenylalanine diet, supplemented with phenylalanine-free amino acid mixtures and special low-protein foods) remains the mainstay of the treatment. Data considering nutrient contents of cooked dishes is lacking. In this study, fourteen dishes specifically prepared for PKU individuals were analysed, regarding the lipid profile and iron and zinc contents. These dishes are poor sources of essential nutrients like Fe, Zn or n-3 fatty acids, reinforcing the need for adequate supplementation to cover individual patients' needs. This study can contribute to a more accurate adjustment of PKU diets and supplementation in order to prevent eventual nutritional deficiencies. This study contributes to a better understanding of nutrient intake from PKU patients' meals, showing the need for dietary supplementation.
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Affiliation(s)
- Filipa B Pimentel
- REQUIMTE/Departamento de Ciências Químicas, Faculdade de Farmácia da Universidade do Porto, Rua de Jorge Viterbo Ferreira no. 228, 4050-313 Porto, Portugal
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32
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Vela-Amieva M, Abreu-González M, González-del Angel A, Ibarra-González I, Fernández-Lainez C, Barrientos-Ríos R, Monroy-Santoyo S, Guillén-López S, Alcántara-Ortigoza MA. Phenylalanine hydroxylase deficiency in Mexico: genotype-phenotype correlations, BH4 responsiveness and evidence of a founder effect. Clin Genet 2015; 88:62-7. [PMID: 24941924 DOI: 10.1111/cge.12444] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 06/13/2014] [Accepted: 06/16/2014] [Indexed: 11/27/2022]
Abstract
The mutational spectrum of the phenylalanine hydroxylase gene (PAH) in Mexico is unknown, although it has been suggested that PKU variants could have a differential geographical distribution. Genotype-phenotype correlations and genotype-based predictions of responsiveness to tetrahydrobiopterin (BH4 ) have never been performed. We sequenced the PAH gene and determined the geographic origin of each allele, mini-haplotype associated, genotype-phenotype correlations and genotype-based prediction of BH4 responsiveness in 48 Mexican patients. The mutational spectrum included 34 variants with c.60+5G>T being the most frequent (20.8%) and linked to haplotype 4.3 possibly because of a founder effect and/or genetic drift. Two new variants were found c.1A>T and c.969+6T>C. The genotype-phenotype correlation was concordant in 70.8%. The genotype-based prediction to BH4 -responsiveness was 41.7%, this information could be useful for the rational selection of candidates for BH4 testing and therapy.
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Affiliation(s)
- M Vela-Amieva
- Laboratorio de Errores Innatos del Metabolismo y Tamiz, Instituto Nacional de Pediatría, Secretaría de Salud, México
| | - M Abreu-González
- Programa de Maestría y Doctorado en Ciencias Biológicas, Facultad de Ciencias, Universidad Nacional Autónoma de México, México D.F., México
| | - A González-del Angel
- Laboratorio de Biología Molecular, Departamento de Genética Humana, Instituto Nacional de Pediatría, Secretaría de Salud, México
| | - I Ibarra-González
- Unidad de Genética de la Nutrición, Instituto de Investigaciones Biomédicas, UNAM - Instituto Nacional de Pediatría, Secretaría de Salud, México
| | - C Fernández-Lainez
- Laboratorio de Errores Innatos del Metabolismo y Tamiz, Instituto Nacional de Pediatría, Secretaría de Salud, México
| | - R Barrientos-Ríos
- Laboratorio de Biología Molecular, Departamento de Genética Humana, Instituto Nacional de Pediatría, Secretaría de Salud, México
| | - S Monroy-Santoyo
- Laboratorio de Errores Innatos del Metabolismo y Tamiz, Instituto Nacional de Pediatría, Secretaría de Salud, México
| | - S Guillén-López
- Laboratorio de Errores Innatos del Metabolismo y Tamiz, Instituto Nacional de Pediatría, Secretaría de Salud, México
| | - M A Alcántara-Ortigoza
- Laboratorio de Biología Molecular, Departamento de Genética Humana, Instituto Nacional de Pediatría, Secretaría de Salud, México
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33
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Danecka MK, Woidy M, Zschocke J, Feillet F, Muntau AC, Gersting SW. Mapping the functional landscape of frequent phenylalanine hydroxylase (PAH) genotypes promotes personalised medicine in phenylketonuria. J Med Genet 2015; 52:175-85. [PMID: 25596310 DOI: 10.1136/jmedgenet-2014-102621] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
BACKGROUND In phenylketonuria, genetic heterogeneity, frequent compound heterozygosity, and the lack of functional data for phenylalanine hydroxylase genotypes hamper reliable phenotype prediction and individualised treatment. METHODS A literature search revealed 690 different phenylalanine hydroxylase genotypes in 3066 phenylketonuria patients from Europe and the Middle East. We determined phenylalanine hydroxylase function of 30 frequent homozygous and compound heterozygous genotypes covering 55% of the study population, generated activity landscapes, and assessed the phenylalanine hydroxylase working range in the metabolic (phenylalanine) and therapeutic (tetrahydrobiopterin) space. RESULTS Shared patterns in genotype-specific functional landscapes were linked to biochemical and pharmacological phenotypes, where (1) residual activity below 3.5% was associated with classical phenylketonuria unresponsive to pharmacological treatment; (2) lack of defined peak activity induced loss of response to tetrahydrobiopterin; (3) a higher cofactor need was linked to inconsistent clinical phenotypes and low rates of tetrahydrobiopterin response; and (4) residual activity above 5%, a defined peak of activity, and a normal cofactor need were associated with pharmacologically treatable mild phenotypes. In addition, we provide a web application for retrieving country-specific information on genotypes and genotype-specific phenylalanine hydroxylase function that warrants continuous extension, updates, and research on demand. CONCLUSIONS The combination of genotype-specific functional analyses with biochemical, clinical, and therapeutic data of individual patients may serve as a powerful tool to enable phenotype prediction and to establish personalised medicine strategies for dietary regimens and pharmacological treatment in phenylketonuria.
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Affiliation(s)
- Marta K Danecka
- Department of Molecular Pediatrics, Dr. von Hauner Children's Hospital, Ludwig-Maximilians-University, Munich, Germany
| | - Mathias Woidy
- Department of Molecular Pediatrics, Dr. von Hauner Children's Hospital, Ludwig-Maximilians-University, Munich, Germany
| | - Johannes Zschocke
- Division of Human Genetics, Medical University Innsbruck, Innsbruck, Austria
| | - François Feillet
- Department of Pediatrics, Hôpital d'Enfants Brabois, CHU Nancy, Vandoeuvre les Nancy, France
| | - Ania C Muntau
- University Children's Hospital, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Søren W Gersting
- Department of Molecular Pediatrics, Dr. von Hauner Children's Hospital, Ludwig-Maximilians-University, Munich, Germany
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Abstract
Detection of individuals with phenylketonuria (PKU), an autosomal recessively inherited disorder in phenylalanine degradation, is straightforward and efficient due to newborn screening programs. A recent introduction of the pharmacological treatment option emerged rapid development of molecular testing. However, variants responsible for PKU do not all suppress enzyme activity to the same extent. A spectrum of over 850 variants, gives rise to a continuum of hyperphenylalaninemia from very mild, requiring no intervention, to severe classical PKU, requiring urgent intervention. Locus-specific and genotypes database are today an invaluable resource of information for more efficient classification and management of patients. The high-tech molecular methods allow patients' genotype to be obtained in a few days, especially if each laboratory develops a panel for the most frequent variants in the corresponding population.
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Affiliation(s)
- Nenad Blau
- Division of Inborn Metabolic Diseases, University Children's Hospital, Im Neuenheimer Feld 430, 69120 Heidelberg, Germany
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Muntau AC, Leandro J, Staudigl M, Mayer F, Gersting SW. Innovative strategies to treat protein misfolding in inborn errors of metabolism: pharmacological chaperones and proteostasis regulators. J Inherit Metab Dis 2014; 37:505-23. [PMID: 24687294 DOI: 10.1007/s10545-014-9701-z] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 02/19/2014] [Accepted: 02/24/2014] [Indexed: 10/25/2022]
Abstract
To attain functionality, proteins must fold into their three-dimensional native state. The intracellular balance between protein synthesis, folding, and degradation is constantly challenged by genetic or environmental stress factors. In the last ten years, protein misfolding induced by missense mutations was demonstrated to be the seminal molecular mechanism in a constantly growing number of inborn errors of metabolism. In these cases, loss of protein function results from early degradation of missense-induced misfolded proteins. Increasing knowledge on the proteostasis network and the protein quality control system with distinct mechanisms in different compartments of the cell paved the way for the development of new treatment strategies for conformational diseases using small molecules. These comprise proteostasis regulators that enhance the capacity of the proteostasis network and pharmacological chaperones that specifically bind and rescue misfolded proteins by conformational stabilization. They can be used either alone or in combination, the latter to exploit synergistic effects. Many of these small molecule compounds currently undergo preclinical and clinical pharmaceutical development and two have been approved: saproterin dihydrochloride for the treatment of phenylketonuria and tafamidis for the treatment of transthyretin-related hereditary amyloidosis. Different technologies are exploited for the discovery of new small molecule compounds that belong to the still young class of pharmaceutical products discussed here. These compounds may in the near future improve existing treatment strategies or even offer a first-time treatment to patients suffering from nowadays-untreatable inborn errors of metabolism.
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Affiliation(s)
- Ania C Muntau
- Department of Molecular Pediatrics, Dr von Hauner Children's Hospital, Ludwig Maximilians University, Lindwurmstrasse 4, 80337, Munich, Germany,
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36
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Camp KM, Parisi MA, Acosta PB, Berry GT, Bilder DA, Blau N, Bodamer OA, Brosco JP, Brown CS, Burlina AB, Burton BK, Chang CS, Coates PM, Cunningham AC, Dobrowolski SF, Ferguson JH, Franklin TD, Frazier DM, Grange DK, Greene CL, Groft SC, Harding CO, Howell RR, Huntington KL, Hyatt-Knorr HD, Jevaji IP, Levy HL, Lichter-Konecki U, Lindegren ML, Lloyd-Puryear MA, Matalon K, MacDonald A, McPheeters ML, Mitchell JJ, Mofidi S, Moseley KD, Mueller CM, Mulberg AE, Nerurkar LS, Ogata BN, Pariser AR, Prasad S, Pridjian G, Rasmussen SA, Reddy UM, Rohr FJ, Singh RH, Sirrs SM, Stremer SE, Tagle DA, Thompson SM, Urv TK, Utz JR, van Spronsen F, Vockley J, Waisbren SE, Weglicki LS, White DA, Whitley CB, Wilfond BS, Yannicelli S, Young JM. Phenylketonuria Scientific Review Conference: state of the science and future research needs. Mol Genet Metab 2014; 112:87-122. [PMID: 24667081 DOI: 10.1016/j.ymgme.2014.02.013] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 02/25/2014] [Accepted: 02/26/2014] [Indexed: 01/17/2023]
Abstract
New developments in the treatment and management of phenylketonuria (PKU) as well as advances in molecular testing have emerged since the National Institutes of Health 2000 PKU Consensus Statement was released. An NIH State-of-the-Science Conference was convened in 2012 to address new findings, particularly the use of the medication sapropterin to treat some individuals with PKU, and to develop a research agenda. Prior to the 2012 conference, five working groups of experts and public members met over a 1-year period. The working groups addressed the following: long-term outcomes and management across the lifespan; PKU and pregnancy; diet control and management; pharmacologic interventions; and molecular testing, new technologies, and epidemiologic considerations. In a parallel and independent activity, an Evidence-based Practice Center supported by the Agency for Healthcare Research and Quality conducted a systematic review of adjuvant treatments for PKU; its conclusions were presented at the conference. The conference included the findings of the working groups, panel discussions from industry and international perspectives, and presentations on topics such as emerging treatments for PKU, transitioning to adult care, and the U.S. Food and Drug Administration regulatory perspective. Over 85 experts participated in the conference through information gathering and/or as presenters during the conference, and they reached several important conclusions. The most serious neurological impairments in PKU are preventable with current dietary treatment approaches. However, a variety of more subtle physical, cognitive, and behavioral consequences of even well-controlled PKU are now recognized. The best outcomes in maternal PKU occur when blood phenylalanine (Phe) concentrations are maintained between 120 and 360 μmol/L before and during pregnancy. The dietary management treatment goal for individuals with PKU is a blood Phe concentration between 120 and 360 μmol/L. The use of genotype information in the newborn period may yield valuable insights about the severity of the condition for infants diagnosed before maximal Phe levels are achieved. While emerging and established genotype-phenotype correlations may transform our understanding of PKU, establishing correlations with intellectual outcomes is more challenging. Regarding the use of sapropterin in PKU, there are significant gaps in predicting response to treatment; at least half of those with PKU will have either minimal or no response. A coordinated approach to PKU treatment improves long-term outcomes for those with PKU and facilitates the conduct of research to improve diagnosis and treatment. New drugs that are safe, efficacious, and impact a larger proportion of individuals with PKU are needed. However, it is imperative that treatment guidelines and the decision processes for determining access to treatments be tied to a solid evidence base with rigorous standards for robust and consistent data collection. The process that preceded the PKU State-of-the-Science Conference, the conference itself, and the identification of a research agenda have facilitated the development of clinical practice guidelines by professional organizations and serve as a model for other inborn errors of metabolism.
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Affiliation(s)
- Kathryn M Camp
- Office of Dietary Supplements, National Institutes of Health, Bethesda, MD 20982, USA.
| | - Melissa A Parisi
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | | | - Gerard T Berry
- Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
| | - Deborah A Bilder
- Department of Psychiatry, University of Utah, Salt Lake City, UT 84108, USA.
| | - Nenad Blau
- University Children's Hospital, Heidelberg, Germany; University Children's Hospital, Zürich, Switzerland.
| | - Olaf A Bodamer
- University of Miami Miller School of Medicine, Miami, FL 33136, USA.
| | - Jeffrey P Brosco
- University of Miami Mailman Center for Child Development, Miami, FL 33101, USA.
| | | | | | - Barbara K Burton
- Ann and Robert H. Lurie Children's Hospital of Chicago, Chicago, IL 60611, USA.
| | - Christine S Chang
- Agency for Healthcare Research and Quality, Rockville, MD 20850, USA.
| | - Paul M Coates
- Office of Dietary Supplements, National Institutes of Health, Bethesda, MD 20982, USA.
| | - Amy C Cunningham
- Tulane University Medical School, Hayward Genetics Center, New Orleans, LA 70112, USA.
| | | | - John H Ferguson
- Office of Rare Diseases Research, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20982, USA.
| | | | | | - Dorothy K Grange
- Washington University School of Medicine, St. Louis Children's Hospital, St. Louis, MO 63110, USA.
| | - Carol L Greene
- University of Maryland School of Medicine, Baltimore, MD 21201, USA.
| | - Stephen C Groft
- Office of Rare Diseases Research, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20982, USA.
| | - Cary O Harding
- Oregon Health & Science University, Portland, OR 97239, USA.
| | - R Rodney Howell
- University of Miami Miller School of Medicine, Miami, FL 33136, USA.
| | | | - Henrietta D Hyatt-Knorr
- Office of Rare Diseases Research, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20982, USA.
| | - Indira P Jevaji
- Office of Research on Women's Health, National Institutes of Health, Bethesda, MD 20817, USA.
| | - Harvey L Levy
- Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
| | - Uta Lichter-Konecki
- George Washington University, Children's National Medical Center, Washington, DC 20010, USA.
| | | | | | | | | | - Melissa L McPheeters
- Vanderbilt Evidence-based Practice Center, Institute for Medicine and Public Health, Nashville, TN 37203, USA.
| | - John J Mitchell
- McGill University Health Center, Montreal, Quebec H3H 1P3, Canada.
| | - Shideh Mofidi
- Maria Fareri Children's Hospital of Westchester Medical Center, Valhalla, NY 10595, USA.
| | - Kathryn D Moseley
- University of Southern California Keck School of Medicine, Los Angeles, CA 90033, USA.
| | - Christine M Mueller
- Office of Orphan Products Development, U.S. Food and Drug Administration, Silver Spring, MD 20993, USA.
| | - Andrew E Mulberg
- Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD 20993, USA.
| | - Lata S Nerurkar
- Office of Rare Diseases Research, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20982, USA.
| | - Beth N Ogata
- University of Washington, Seattle, WA 98195, USA.
| | - Anne R Pariser
- Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD 20993, USA.
| | - Suyash Prasad
- BioMarin Pharmaceutical Inc., San Rafael, CA 94901, USA.
| | - Gabriella Pridjian
- Tulane University Medical School, Hayward Genetics Center, New Orleans, LA 70112, USA.
| | | | - Uma M Reddy
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | | | | | - Sandra M Sirrs
- Vancouver General Hospital, University of British Columbia, Vancouver V5Z 1M9, Canada.
| | | | - Danilo A Tagle
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Susan M Thompson
- The Children's Hospital at Westmead, Sydney, NSW 2145, Australia.
| | - Tiina K Urv
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Jeanine R Utz
- University of Minnesota, Minneapolis, MN 55455, USA.
| | - Francjan van Spronsen
- University of Groningen, University Medical Center of Groningen, Beatrix Children's Hospital, Netherlands.
| | - Jerry Vockley
- University of Pittsburgh, Pittsburgh, PA 15224, USA.
| | - Susan E Waisbren
- Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
| | - Linda S Weglicki
- National Institute of Nursing Research, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Desirée A White
- Department of Psychology, Washington University, St. Louis, MO 63130, USA.
| | | | - Benjamin S Wilfond
- Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, WA 98101, USA.
| | | | - Justin M Young
- The Young Face, Facial Plastic and Reconstructive Surgery, Cumming, GA 30041, USA.
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Ho G, Alexander I, Bhattacharya K, Dennison B, Ellaway C, Thompson S, Wilcken B, Christodoulou J. The Molecular Bases of Phenylketonuria (PKU) in New South Wales, Australia: Mutation Profile and Correlation with Tetrahydrobiopterin (BH4) Responsiveness. JIMD Rep 2013; 14:55-65. [PMID: 24368688 DOI: 10.1007/8904_2013_284] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 11/20/2013] [Accepted: 11/22/2013] [Indexed: 12/24/2022] Open
Abstract
Phenylketonuria (PKU) is an autosomal recessive inborn error of phenylalanine metabolism predominantly caused by mutations in the phenylalanine hydroxylase (PAH) gene. Mutation screening was carried out in a large cohort of PKU patients from New South Wales, Australia. Pathogenic mutations were identified in 99% of the alleles screened, with the two most common mutations (p.R408W and IVS12+1G>A) accounting for 30.7% of alleles. Most individuals were compound heterozygotes for previously reported mutations, but four novel mutations (c.163+1G>T, c.164-2A>G, c.461A>T [p.Y154F], and c.510-1G>A) and a novel polymorphism (c.60+62C>T) were also identified. A number of patients have been previously tested for their response to dietary supplementation of tetrahydrobiopterin (BH4), the cofactor of PAH. Correlation between genotype and the responses revealed that although genotype is a major determinant of BH4 responsiveness, patients with the same genotype may also show disparate responses to this treatment. A clinical and biochemical evaluation should be undertaken to determine the effectiveness of PKU treatment by supplementation of BH4.
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Affiliation(s)
- Gladys Ho
- Genetic Metabolic Disorders Research Unit, Children's Hospital at Westmead, Locked Bag 4001, Westmead, NSW, 2145, Australia
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Polak E, Ficek A, Radvanszky J, Soltysova A, Urge O, Cmelova E, Kantarska D, Kadasi L. Phenylalanine hydroxylase deficiency in the Slovak population: genotype-phenotype correlations and genotype-based predictions of BH4-responsiveness. Gene 2013; 526:347-55. [PMID: 23764561 DOI: 10.1016/j.gene.2013.05.057] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Revised: 05/08/2013] [Accepted: 05/20/2013] [Indexed: 10/26/2022]
Abstract
We investigated the mutation spectrum of the phenylalanine hydroxylase gene (PAH) in a cohort of patients from 135 Slovak PKU families. Mutational screening of the known coding region, including conventional intron splice sites, was performed using high-resolution melting analysis, with subsequent sequencing analysis of the samples showing deviated melting profiles compared to control samples. The PAH gene was also screened for deletions and duplications using MLPA analysis. Forty-eight different disease causing mutations were identified in our patient group, including 30 missense, 8 splicing, 7 nonsense, 2 large deletions and 1 small deletion with frameshift; giving a detection rate of 97.6%. The most prevalent mutation was the p.R408W, occurring in 47% of all alleles, which concurs with results from neighboring and other Slavic countries. Other frequent mutations were: p.R158Q (5.3%), IVS12+1G>A (5.3%), p.R252W (5.1%), p.R261Q (3.9%) and p.A403V (3.6%). We also identified three novel missense mutations: p.F233I, p.R270I, p.F331S and one novel variant: c.-30A>T in the proximal part of the PAH gene promoter. A spectrum of 84 different genotypes was observed and a genotype based predictions of BH4-responsiveness were assessed. Among all genotypes, 36 were predicted to be BH4-responsive represented by 51 PKU families. In addition, genotype-phenotype correlations were performed.
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Affiliation(s)
- Emil Polak
- Comenius University, Faculty of Natural Sciences, Department of Molecular Biology, Mlynska Dolina, 842 15 Bratislava, Slovak Republic.
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Abstract
INTRODUCTION Phenylketonuria (PKU) is caused by mutation of the enzyme, phenylalanine (Phe) hydroxylase (PAH). The hyperphenylalaninemia characteristic of PKU causes devastating neurological damage if not identified and treated at birth with a Phe-restricted diet. Sapropterin dihydrochloride, a pharmaceutical formulation of the natural cofactor for PAH (6R-tetrahydrobiopterin; BH4), is now available for the management of hyperphenylalaninemia in some PKU patients, including BH4 deficiencies. Sapropterin dihydrochloride improves dietary Phe tolerance in about 20% of patients with PKU. AREAS COVERED This evaluation describes the identification of patients suitable for treatment of sapropterin dihydrochloride, together with its indications, therapeutic properties and efficacy. Furthermore, the article reviews its safety and tolerability in patients with PKU or BH4 deficiency. EXPERT OPINION A reduction in blood Phe of at least 30% occurred in ∼ 20 - 30% of sapropterin-treated PKU patients (mostly with milder forms of PKU). Treatment with sapropterin resulted in clinically significant and sustained reductions in blood Phe concentrations and increased dietary Phe tolerance in well-designed clinical studies in PKU patients who responded to BH4. Successful treatment with sapropterin may lead to a relaxation of the Phe-restricted diet, although continued monitoring of blood Phe is required. Sapropterin was well tolerated.
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Affiliation(s)
- Nenad Blau
- University Children's Hospital, Division of Inborn Metabolic Diseases, Department of General Pediatrics, Im Neuenheimer Feld 430, 69120 Heidelberg, Germany.
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Anjema K, van Rijn M, Hofstede FC, Bosch AM, Hollak CEM, Rubio-Gozalbo E, de Vries MC, Janssen MCH, Boelen CCA, Burgerhof JGM, Blau N, Heiner-Fokkema MR, van Spronsen FJ. Tetrahydrobiopterin responsiveness in phenylketonuria: prediction with the 48-hour loading test and genotype. Orphanet J Rare Dis 2013; 8:103. [PMID: 23842451 PMCID: PMC3711849 DOI: 10.1186/1750-1172-8-103] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 07/01/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND How to efficiently diagnose tetrahydrobiopterin (BH4) responsiveness in patients with phenylketonuria remains unclear. This study investigated the positive predictive value (PPV) of the 48-hour BH4 loading test and the additional value of genotype. METHODS Data of the 48-hour BH4 loading test (20 mg BH4/kg/day) were collected at six Dutch university hospitals. Patients with ≥30% phenylalanine reduction at ≥1 time points during the 48 hours (potential responders) were invited for the BH4 extension phase, designed to establish true-positive BH4 responsiveness. This is defined as long-term ≥30% reduction in mean phenylalanine concentration and/or ≥4 g/day and/or ≥50% increase of natural protein intake. Genotype was collected if available. RESULTS 177/183 patients successfully completed the 48-hour BH4 loading test. 80/177 were potential responders and 67/80 completed the BH4 extension phase. In 58/67 true-positive BH4 responsiveness was confirmed (PPV 87%). The genotype was available for 120/177 patients. 41/44 patients with ≥1 mutation associated with long-term BH4 responsiveness showed potential BH4 responsiveness in the 48-hour test and 34/41 completed the BH4 extension phase. In 33/34 true-positive BH4 responsiveness was confirmed. 4/40 patients with two known putative null mutations were potential responders; 2/4 performed the BH4 extension phase but showed no true-positive BH4 responsiveness. CONCLUSIONS The 48-hour BH4 loading test in combination with a classified genotype is a good parameter in predicting true-positive BH4 responsiveness. We propose assessing genotype first, particularly in the neonatal period. Patients with two known putative null mutations can be excluded from BH4 testing.
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Affiliation(s)
- Karen Anjema
- Division of Metabolic Diseases, University Medical Center Groningen, Beatrix Children’s Hospital CA33, PO box 30.001, Groningen 9700 RB, The Netherlands
| | - Margreet van Rijn
- Division of Metabolic Diseases, University Medical Center Groningen, Beatrix Children’s Hospital CA33, PO box 30.001, Groningen 9700 RB, The Netherlands
| | - Floris C Hofstede
- University Medical Center Utrecht, Wilhelmina Children’s Hospital, Utrecht, The Netherlands
| | - Annet M Bosch
- Academic Medical Center, University Hospital of Amsterdam, Amsterdam, The Netherlands
| | - Carla EM Hollak
- Academic Medical Center, University Hospital of Amsterdam, Amsterdam, The Netherlands
| | | | - Maaike C de Vries
- Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
| | - Mirian CH Janssen
- Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
| | | | - Johannes GM Burgerhof
- Division of Metabolic Diseases, University Medical Center Groningen, Beatrix Children’s Hospital CA33, PO box 30.001, Groningen 9700 RB, The Netherlands
| | - Nenad Blau
- University Children’s Hospital, Heidelberg, Germany
- University Children’s Hospital, Zürich, Switzerland
| | - M Rebecca Heiner-Fokkema
- Division of Metabolic Diseases, University Medical Center Groningen, Beatrix Children’s Hospital CA33, PO box 30.001, Groningen 9700 RB, The Netherlands
| | - Francjan J van Spronsen
- Division of Metabolic Diseases, University Medical Center Groningen, Beatrix Children’s Hospital CA33, PO box 30.001, Groningen 9700 RB, The Netherlands
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Heintz C, Cotton RGH, Blau N. Tetrahydrobiopterin, its mode of action on phenylalanine hydroxylase, and importance of genotypes for pharmacological therapy of phenylketonuria. Hum Mutat 2013; 34:927-36. [PMID: 23559577 DOI: 10.1002/humu.22320] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 03/20/2013] [Accepted: 03/20/2013] [Indexed: 11/11/2022]
Abstract
In about 20%-30% of phenylketonuria (PKU) patients (all phenotypes of PAH deficiency), Phe levels may be controlled through phenylalanine hydroxylase cofactor tetrahydrobiopterin therapy. These patients can be diagnosed by an oral tetrahydrobiopterin challenge and are characterized by mutations coding for proteins with substantial residual PAH activity. They can be treated with a commercially available synthetic form of tetrahydrobiopterin, either as a monotherapy or as adjunct to the diet. This review article summarizes molecular and metabolic bases of PKU and the importance of the tetrahydrobiopterin loading test used for PKU patients. On the basis of in vitro residual PAH activity, more than 1,200 genotypes from patients challenged with tetrahydrobiopterin were categorized as predictive for tetrahydrobiopterin responsiveness or non-responsiveness and correlated with the loading test, phenotype, and residual in vitro PAH activity. The coexpression of two distinct PAH mutant alleles revealed possible dominance effects (positive or negative) by one of the mutations on residual activity as result of interallelic complementation. The treatment of the transfected cells with tetrahydrobiopterin showed an increase in residual PAH activity with several mutations coexpressed.
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Keil S, Anjema K, van Spronsen FJ, Lambruschini N, Burlina A, Bélanger-Quintana A, Couce ML, Feillet F, Cerone R, Lotz-Havla AS, Muntau AC, Bosch AM, Meli CAP, Billette de Villemeur T, Kern I, Riva E, Giovannini M, Damaj L, Leuzzi V, Blau N. Long-term follow-up and outcome of phenylketonuria patients on sapropterin: a retrospective study. Pediatrics 2013; 131:e1881-8. [PMID: 23690520 DOI: 10.1542/peds.2012-3291] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVE Sapropterin dihydrochloride, the synthetic form of 6R-tetrahydrobiopterin (BH4), is an approved drug for the treatment of patients with BH4-responsive phenylketonuria (PKU). The purpose of this study was to assess genotypes and data on the long-term effects of BH4/sapropterin on metabolic control and patient-related outcomes in 6 large European countries. METHODS A questionnaire was developed to assess phenotype, genotype, blood phenylalanine (Phe) levels, Phe tolerance, quality of life, mood changes, and adherence to diet in PKU patients from 16 medical centers. RESULTS One hundred forty-seven patients, of whom 41.9% had mild hyperphenylalaninemia, 50.7% mild PKU, and 7.4% classic PKU, were followed up over ≤12 years. A total of 85 different genotypes were reported. With the exception of two splice variants, all of the most common mutations were reported to be associated with substantial residual Phe hydroxylase activity. Median Phe tolerance increased 3.9 times with BH4/sapropterin therapy, compared with dietary treatment, and median Phe blood concentrations were within the therapeutic range in all patients. Compared with diet alone, improvement in quality of life was reported in 49.6% of patients, improvement in adherence to diet was reported in 47% of patients, and improvement in adherence to treatment was reported in 63.3% of patients. No severe adverse events were reported. CONCLUSIONS Our data document a long-term beneficial effect of orally administered BH4/sapropterin in responsive PKU patients by improving the metabolic control, increasing daily tolerance for dietary Phe intake, and for some, by improving dietary adherence and quality of life. Patient genotypes help in predicting BH4 responsiveness.
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Affiliation(s)
- Stefanie Keil
- Division of Inborn Metabolic Diseases, University Children's Hospital, Heidelberg, Germany
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Bueno MA, González-Lamuño D, Delgado-Pecellín C, Aldámiz-Echevarría L, Pérez B, Desviat LR, Couce ML. Molecular epidemiology and genotype-phenotype correlation in phenylketonuria patients from South Spain. J Hum Genet 2013; 58:279-84. [PMID: 23514811 DOI: 10.1038/jhg.2013.16] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The aim of this study was to identify the most common genotypes in the phenylketonuria (PKU) population of Andalusia, assessing the correlation with the phenotype and the usefulness in predicting the response to treatment with tetrahydrobiopterin. We conducted a retrospective observational study between January 1980 and January 2010 in 147 Andalusian PKU patients assessing phenotype, genotype and response to a 24-h BH4 loading test. Our cohort of patients exhibited 65 different mutations, 69.2% corresponding to the missense type, in a total of 123 different genotypes. IVS10nt-11g>a was the most common mutation (10.9%). Four novel missense mutations were identified: p.L258P; p.E66K, p.R155C and p.P122S. Although generally there is a good genotype-phenotype correlation, for eight of the repeated genotypes a slightly different phenotype was observed. In 96 PKU subjects BH4 challenge was carried out. Patients with previously reported unresponsive mutations on both alleles showed a negative response, while 95.5% (28/29) of the responsive patients carry at least one missense mutation previously associated to the BH4. Our data reveal a great genetic heterogeneity in the Andalusian population. Genotype is quite a good predictor of the phenotype and of the responsiveness to tetrahydrobiopterin, which is relevant for patient management and follow-up.
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Affiliation(s)
- María A Bueno
- Unit of Metabolophaties and Nutrition, Department of Pediatrics, Hospital Universitario Virgen del Rocio, Seville, Spain
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Cerone R, Andria G, Giovannini M, Leuzzi V, Riva E, Burlina A. Testing for tetrahydrobiopterin responsiveness in patients with hyperphenylalaninemia due to phenylalanine hydroxylase deficiency. Adv Ther 2013; 30:212-28. [PMID: 23436109 DOI: 10.1007/s12325-013-0011-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Indexed: 10/27/2022]
Abstract
INTRODUCTION Pharmacological levels of the phenylalanine hydroxylase enzyme cofactor, tetrahydrobiopterin (BH4), reduce plasma phenylalanine levels in some patients with phenylketonuria (PKU), providing the first pharmacological therapy for PKU. Responsiveness to this therapy must be determined empirically through a BH4 loading test or trial. The authors have analyzed the loading tests currently in use in light of the numerous factors that can influence their results. Sapropterin dihydrochloride is a stable, synthetic form of BH4 approved for treatment of PKU in responsive patients. METHODS An expert panel identified evidence from published reports of clinical experience. Reports of research involving at least 25 patients and published in English were considered. RESULTS In all, 14 studies met both criteria; eight employing the sapropterin dihydrochloride preparation from Schircks Laboratories and six the sapropterin dihydrochloride preparation from Biomarin/Merck Serono. CONCLUSION The arbitrary responsiveness definition of a >30% reduction in blood phenylalanine appears to be a good compromise between sensitivity and specificity for the initial screening test. However, individual patient characteristics should be considered when interpreting results, especially in patients with low baseline phenylalanine levels.
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Affiliation(s)
- Roberto Cerone
- Reference Center for Neonatal Screening and Diagnosis for Metabolic Diseases of University-Istituto Giannina Gaslini, Via 5 maggio, 3916147 Genoa, Italy.
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Wiedemann A, Leheup B, Battaglia-Hsu SF, Jonveaux P, Jeannesson E, Feillet F. Undiagnosed phenylketonuria in parents of phenylketonuric patients, is it worthwhile to be checked? Mol Genet Metab 2013; 110 Suppl:S62-5. [PMID: 24051226 DOI: 10.1016/j.ymgme.2013.08.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Revised: 08/25/2013] [Accepted: 08/25/2013] [Indexed: 10/26/2022]
Abstract
In our phenylketonuria (PKU) cohort of 120 patients, we uncovered a couple of cases of undiagnosed mild phenylketonuria (mPKU)/hyperphenylalaninemia (mHPA) in maternal parents of the PKU cohort. This finding prompted us to evaluate the risk of either mild phenylketonuria or mild hyperphenylalaninemia in the parent population whose children were diagnosed with hyperphenylalaninemia (HPA). Taking into account the phenylalanine hydroxylase (PAH) mutation carrier frequency and the PAH mild mutation rate, we estimated that the prevalence of the parental mPKU/mHPA varied widely, from 1/74 in Turkey to 1/708 in Lithuania. The benefits of the parental detection procedure described here are the prevention of further maternal PKU syndrome, the follow-up of the newly detected patients and the accuracy of the genetic counseling provided to these families. This very simple procedure should be incorporated into neonatal PKU management of the hospitals in countries where a routine systematic neonatal screening is operational.
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Affiliation(s)
- A Wiedemann
- CHU Brabois, Pôle Enfants, Service de Pédiatrie et de Génétique Clinique, Vandoeuvre les Nancy 54500, France
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Karam PE, Alhamra RS, Nemer G, Usta J. Spectrum of mutations in Lebanese patients with phenylalanine hydroxylase deficiency. Gene 2012; 515:117-22. [PMID: 23220018 DOI: 10.1016/j.gene.2012.11.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 11/15/2012] [Accepted: 11/20/2012] [Indexed: 11/24/2022]
Abstract
Phenylketonuria is an autosomal recessive inborn error of metabolism resulting from phenylalanine hydroxylase deficiency. Genetic basis of phenylalanine hydroxylase deficiency has been reported in various European and Asian countries with few reports available in Arab populations of the Mediterranean region. This is the first pilot study describing phenotype and genotype of 23 Lebanese patients with phenylketonuria. 48% of the patients presented mainly with neurological signs at a mean age of 2 years 9 months, as newborn screening is not yet a nationwide policy. 56.5% of the patients had classical phenylketonuria. Thirteen different mutations were identified: splice site 52%, frameshift 31%, and missense 17% with no nonsense mutations. IVS10-11G>A was found mainly in Christians at high relative frequency whereas Muslims carried the G352fs and R261Q mutations. A rare splice mutation IVS7+1G>T, not described before, was identified in the homozygous state in one family with moderate phenylketonuria phenotype. Genotype-phenotype correlation using Guldberg arbitrary value method showed high consistency between predicted and observed phenotypes. Calculated homozygosity rate was 0.07 indicating the genetic heterogeneity in our patients. Our findings underline the admixture of different ethnicities and religions in Lebanon that might help tracing back the PAH gene flux history across the Mediterranean region.
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Affiliation(s)
- Pascale E Karam
- Department of Pediatrics and Adolescent, American University Medical Center, Faculty of Medicine, Beirut, Lebanon
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Molecular Genetics and Genotype-Based Estimation of BH4-Responsiveness in Serbian PKU Patients: Spotlight on Phenotypic Implications of p.L48S. JIMD Rep 2012; 9:49-58. [PMID: 23430547 DOI: 10.1007/8904_2012_178] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 09/02/2012] [Accepted: 09/06/2012] [Indexed: 12/31/2022] Open
Abstract
Phenylketonuria (PKU) is caused by mutations in the gene encoding phenylalanine hydroxylase (PAH) enzyme. Here, we report the updated spectrum of PAH mutations in 61 Serbian PKU patients. By using both DGGE/DNA sequencing and PCR-RFLP, we identified 26 disease-causing mutations (detection rate 99%). The most frequent ones were p.L48S (31%), p.R408W (16.4%), p.P281L (6%), p.E390G (5.2%), and p.I306V (5.2%). Homozygosity value indicated high heterogeneity of Serbian population.To overcome possible pitfalls of patients' phenotypic classification, we used two parameters: pretreatment/maximal phenylalanine blood concentration and Phe tolerance. The two phenotypes did not match only for patients with p.L48S. Therefore, we used Mann-Whitney statistical test to compare pretreatment/maximal blood Phe concentration and Phe tolerance detected in patients with p.[L48S];[null] and p.[missense];[null] genotypes. For patients with p.L48S, our results implied that Phe tolerance is a better parameter for phenotypic classification. Also, Fisher's exact test was used to compare p.L48S effect on phenotype of homozygous and functionally hemizygous patients. Our findings showed that effect of p.L48S was altered in functional hemizygotes. Moreover, phenotypic inconsistency found in homozygotes suggested that interallelic complementation and/or additional factors play a role in genotype-phenotype correlation.Since BH4-supplementation therapy is not available in Serbia, we made the first estimation of its potential benefit based on patients' genotypes. In the analyzed cohort, the total frequency of BH4-responsive mutations was 52.6%. Furthermore, we found a significant number of genotypes (26.2% BH4-responsive and 51% probably BH4-responsive) that may respond to BH4 therapy. This led us to a conclusion that BH4-supplementation therapy could bring benefit to Serbian PKU patients.
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Sarkissian CN, Ying M, Scherer T, Thöny B, Martinez A. The mechanism of BH4 -responsive hyperphenylalaninemia--as it occurs in the ENU1/2 genetic mouse model. Hum Mutat 2012; 33:1464-73. [PMID: 22644647 DOI: 10.1002/humu.22128] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2011] [Accepted: 05/15/2012] [Indexed: 01/07/2023]
Abstract
The Pah(enu1/enu2) (ENU1/2) mouse is a heteroallelic orthologous model displaying blood phenylalanine (Phe) concentrations characteristic of mild hyperphenylalaninemia. ENU1/2 mice also have reduced liver phenylalanine hydroxylase (PAH) protein content (∼20% normal) and activity (∼2.5% normal). The mutant PAH protein is highly ubiquitinated, which is likely associated with its increased misfolding and instability. The administration of a single subcutaneous injection of l-Phe (1.1 mg l-Phe/g body weight) leads to an approximately twofold to threefold increase of blood Phe and phenylalanine/tyrosine (Phe/Tyr) ratio, and a 1.6-fold increase of both nonubiquitinated PAH protein content and PAH activity. It also results in elevated concentrations of liver 6R-l-erythro-5,6,7,8-tetrahydrobiopterin (BH(4)), potentially through the influence of Phe on GTP cyclohydrolase I and its feedback regulatory protein. The increased BH(4) content seems to stabilize PAH. Supplementing ENU1/2 mice with BH(4) (50 mg/kg/day for 10 days) reduces the blood Phe/Tyr ratio within the mild hyperphenylalaninemic range; however, PAH content and activity were not elevated. It therefore appears that BH(4) supplementation of ENU1/2 mice increases Phe hydroxylation levels through a kinetic rather than a chaperone stabilizing effect. By boosting blood Phe concentrations, and by BH(4) supplementation, we have revealed novel insights into the processing and regulation of the ENU1/2-mutant PAH.
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Affiliation(s)
- Christineh N Sarkissian
- Department of Human Genetics, McGill University-Montreal Children's Hospital Research Institute, Montreal, Quebec, Canada
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Tansek MZ, Groselj U, Murko S, Kobe H, Lampret BR, Battelino T. Assessment of tetrahydrobiopterin (BH(4))-responsiveness and spontaneous phenylalanine reduction in a phenylalanine hydroxylase deficiency population. Mol Genet Metab 2012; 107:37-42. [PMID: 22917871 DOI: 10.1016/j.ymgme.2012.07.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2012] [Revised: 07/13/2012] [Accepted: 07/13/2012] [Indexed: 11/28/2022]
Abstract
A BH(4) loading test was performed in 36 patients from 34 unrelated families. The patients had 29 different genotypes, and previous data on only eight of them were found in the BIOPKU database. Thirteen patients were classified as classic PKU (35.1%), 14 as mild PKU (37.8%) and 9 as MHP (27.0%). Blood Phe levels were shown to reach a plateau after three full days of increased natural protein ingestion. Measuring the 24-hour blood Phe levels (T(-24), T(-16), T(0)) on the fourth day of increased protein ingestion before BH(4) administration showed that within 24h Phe on average increased by 2.4% in MHP patients, decreased by 2.7% in mild PKU patients and increased by 9.7% in classic PKU patients (NS for all comparisons); Phe only slightly decreased in responders by 0.2% but increased in non-responders by 7.8% (P>0.05). Altogether, 16 of 36 (44.4%) patients represented by 12 of 29 (41.4%) different genotypes were proven to be BH(4) responders, and four (10.8%) were slow-responders. Responders were 6/9 (66.7%) MHP patients, 10/14 (71.4%) mild PKU patients and 0/13 classic PKU patients. Twenty of the 29 (68.9%) genotypes harbored at least one mutation with a known PRA of 10% or more but only 11 (55%) of them were BH(4)-responsive. Spontaneous reduction of blood Phe levels within 24h on the fourth day of natural protein loading was observed only in mild PKU patients and was shown not to be an important part of the BH(4)-response. 73.3% of genotypes containing at least one allele with a PRA of at least 30% were found to be BH(4) responsive; a PRA of at least 15.5% was needed for the responder genotype in our population.
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Affiliation(s)
- Mojca Zerjav Tansek
- Department of Pediatric Endocrinology, Diabetes and Metabolic Diseases, University Children's Hospital, UMC Ljubljana, Ljubljana, Slovenia
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Quirk ME, Dobrowolski SF, Nelson BE, Coffee B, Singh RH. Utility of phenylalanine hydroxylase genotype for tetrahydrobiopterin responsiveness classification in patients with phenylketonuria. Mol Genet Metab 2012; 107:31-6. [PMID: 22841515 PMCID: PMC4029439 DOI: 10.1016/j.ymgme.2012.07.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 07/10/2012] [Accepted: 07/11/2012] [Indexed: 10/28/2022]
Abstract
BACKGROUND A need exists to expand the characterization of tetrahydrobiopterin (BH(4)) responsiveness in patients with phenylketonuria (PKU), beyond simply evaluating change in blood phenylalanine concentrations. The clinical interpretation of BH(4) responsiveness should be evaluated within the context of phenylalanine hydroxylase (PAH) genotype. AIM This investigation seeks to use a modified version of a previously developed PAH genotype severity tool, the assigned value (AV) sum, to assess the molecular basis of responsiveness in a clinical cohort and to explore the tool's ability to differentiate BH(4) responsive groups. METHODS BH(4) response was previously clinically classified in 58 patients with PKU, with three response groups emerging: definitive responders, provisional responders, and non-responders. Provisional responders represented a clinically ambiguous group, with an initial decrease in plasma phenylalanine concentrations, but limited ability to improve dietary phenylalanine tolerance. In this retrospective analysis, mutations in the PAH gene were identified in each patient. PAH genotype was characterized through the AV sum approach, in which each mutation is given an AV of 1, 2, 4, or 8; the sum of both mutations' AV corresponds to genotype severity, with a lower number representing a more severe phenotype. An AV sum cutoff of 2 (indicative of the most severe genotypes) was used to dichotomize patients and predict BH(4) responsiveness. Provisional responders were classified with the definitive responders then the non-responders to see with which group they best aligned. RESULTS In 17/19 definitive responders, at least one mutation was mild or moderate in severity (AV sum>2). In contrast, 7/9 provisional responders carried two severe or null mutations (AV sum=2), suggesting little molecular basis for responsiveness. Non-responders represent a heterogeneous group with 15/25 patients carrying two severe mutations (AV sum=2), 5/25 patients carrying one moderate or mild mutation in combination with a severe or null mutation (AV sum>2), and the remaining five patients carrying an uncharacterized mutation in combination with a severe mutation. Predictive sensitivity of the AV sum was maximized (89.5% vs. 67.9%) with limited detriment to specificity (79.4% vs. 80.0%), by classifying provisional responders with the non-responders rather than with the definitive responders. CONCLUSIONS In our clinical cohort, the AV sum tool was able to identify definitive responders with a high degree of sensitivity. As demonstrated by both the provisional responder group and the substantial number of non-responders with AV sums>2, a potential exists for misclassification when BH(4) response is determined by relying solely on change in plasma phenylalanine concentrations. PAH genotype should be incorporated in the clinical evaluation of BH(4) responsiveness.
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Affiliation(s)
- Meghan E. Quirk
- Division of Biological and Biomedical Sciences, Nutrition and Health Sciences, Emory University, Atlanta, GA, USA
| | - Steven F. Dobrowolski
- Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT, USA
| | | | - Bradford Coffee
- Department of Human Genetics, Emory University School of Medicine, Decatur, GA, USA
| | - Rani H. Singh
- Division of Biological and Biomedical Sciences, Nutrition and Health Sciences, Emory University, Atlanta, GA, USA
- Department of Human Genetics, Emory University School of Medicine, Decatur, GA, USA
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