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Pasquetti D, Gazzellone A, Rossi S, Orteschi D, L’Erario FF, Concolino P, Minucci A, Dionisi-Vici C, Genuardi M, Silvestri G, Chiurazzi P. Triple Genetic Diagnosis in a Patient with Late-Onset Leukodystrophy and Mild Intellectual Disability. Int J Mol Sci 2023; 25:495. [PMID: 38203665 PMCID: PMC10778870 DOI: 10.3390/ijms25010495] [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: 11/27/2023] [Revised: 12/20/2023] [Accepted: 12/28/2023] [Indexed: 01/12/2024] Open
Abstract
We describe the complex case of a 44-year-old man with polycystic kidney disease, mild cognitive impairment, and tremors in the upper limbs. Brain MRI showed lesions compatible with leukodystrophy. The diagnostic process, which included clinical exome sequencing (CES) and chromosomal microarray analysis (CMA), revealed a triple diagnosis: autosomal dominant polycystic kidney disease (ADPKD) due to a pathogenic variant, c.2152C>T-p.(Gln718Ter), in the PKD1 gene; late-onset phenylketonuria due to the presence of two missense variants, c.842C>T-p.(Pro281Leu) and c.143T>C-p.(Leu48Ser) in the PAH gene; and a 915 Kb duplication on chromosome 15. Few patients with multiple concurrent genetic diagnoses are reported in the literature; in this ADPKD patient, genome-wide analysis allowed for the diagnosis of adult-onset phenylketonuria (which would have otherwise gone unnoticed) and a 15q11.2 duplication responsible for cognitive and behavioral impairment with incomplete penetrance. This case underlines the importance of clinical genetics for interpreting complex results obtained by genome-wide techniques, and for diagnosing concurrent late-onset monogenic conditions.
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Affiliation(s)
- Domizia Pasquetti
- Section of Genomic Medicine, Department of Life Sciences and Public Health, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
- Medical Genetics Unit, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy
| | - Annalisa Gazzellone
- Section of Genomic Medicine, Department of Life Sciences and Public Health, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
- Medical Genetics Unit, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy
| | - Salvatore Rossi
- Department of Neurosciences, Faculty of Medicine and Surgery, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
- Neurology Unit, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy
| | - Daniela Orteschi
- Section of Genomic Medicine, Department of Life Sciences and Public Health, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
- Medical Genetics Unit, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy
| | - Federica Francesca L’Erario
- Section of Genomic Medicine, Department of Life Sciences and Public Health, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
- Medical Genetics Unit, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy
| | - Paola Concolino
- Departmental Unit of Molecular and Genomic Diagnostics, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy
| | - Angelo Minucci
- Departmental Unit of Molecular and Genomic Diagnostics, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy
| | - Carlo Dionisi-Vici
- Division of Metabolic Diseases, Bambino Gesù Children’s Hospital IRCCS, 00165 Rome, Italy
| | - Maurizio Genuardi
- Section of Genomic Medicine, Department of Life Sciences and Public Health, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
- Medical Genetics Unit, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy
| | - Gabriella Silvestri
- Department of Neurosciences, Faculty of Medicine and Surgery, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
- Neurology Unit, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy
| | - Pietro Chiurazzi
- Section of Genomic Medicine, Department of Life Sciences and Public Health, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
- Medical Genetics Unit, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy
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2
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Tendi EA, Morello G, Guarnaccia M, La Cognata V, Petralia S, Messina MA, Meli C, Fiumara A, Ruggieri M, Cavallaro S. Detection of Single-Nucleotide and Copy Number Defects Underlying Hyperphenylalaninemia by Next-Generation Sequencing. Biomedicines 2023; 11:1899. [PMID: 37509538 PMCID: PMC10377317 DOI: 10.3390/biomedicines11071899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 06/27/2023] [Accepted: 06/29/2023] [Indexed: 07/30/2023] Open
Abstract
Hyperphenylalaninemia (HPA) is the most common inherited amino acid metabolism disorder characterized by serious clinical manifestations, including irreversible brain damage, intellectual deficiency and epilepsy. Due to its extensive genic and allelic heterogeneity, next-generation sequencing (NGS) technology may help to identify the molecular basis of this genetic disease. Herein, we describe the development and validation of a targeted NGS (tNGS) approach for the simultaneous detection of single-nucleotide changes and copy number variations (CNVs) in genes associated with HPA (PAH, GCH1, PTS, QDPR, PCBD1, DNAJC12) or useful for its differential diagnosis (SPR). Our tNGS approach offers the possibility to detail, with a high accuracy and in a single workflow, the combined effect of a broader spectrum of genomic variants in a comprehensive view, providing a significant step forward in the development of optimized patient care and management.
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Affiliation(s)
- Elisabetta Anna Tendi
- Biomedical Sciences Department, Institute for Biomedical Research and Innovation, National Research Council, Via Paolo Gaifami 18, 95026 Catania, Italy
| | - Giovanna Morello
- Biomedical Sciences Department, Institute for Biomedical Research and Innovation, National Research Council, Via Paolo Gaifami 18, 95026 Catania, Italy
| | - Maria Guarnaccia
- Biomedical Sciences Department, Institute for Biomedical Research and Innovation, National Research Council, Via Paolo Gaifami 18, 95026 Catania, Italy
| | - Valentina La Cognata
- Biomedical Sciences Department, Institute for Biomedical Research and Innovation, National Research Council, Via Paolo Gaifami 18, 95026 Catania, Italy
| | - Salvatore Petralia
- Department of Drug and Health Sciences, University of Catania, 95125 Catania, Italy
| | - Maria Anna Messina
- Regional Reference Center for the Treatment and Control of Congenital Metabolic Diseases of Childhood, Department of Clinical and Experimental Medicine, University Hospital Policlinico "Rodolico-San Marco", 95123 Catania, Italy
| | - Concetta Meli
- Regional Reference Center for the Treatment and Control of Congenital Metabolic Diseases of Childhood, Department of Clinical and Experimental Medicine, University Hospital Policlinico "Rodolico-San Marco", 95123 Catania, Italy
| | - Agata Fiumara
- Regional Reference Center for the Treatment and Control of Congenital Metabolic Diseases of Childhood, Department of Clinical and Experimental Medicine, University Hospital Policlinico "Rodolico-San Marco", 95123 Catania, Italy
| | - Martino Ruggieri
- Unit of Rare Diseases of the Nervous System in Childhood, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University Hospital Policlinico "Rodolico-San Marco", 95123 Catania, Italy
| | - Sebastiano Cavallaro
- Biomedical Sciences Department, Institute for Biomedical Research and Innovation, National Research Council, Via Paolo Gaifami 18, 95026 Catania, Italy
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3
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Fishchuk L, Rossokha Z, Olkhovich N, Pichkur N, Popova O, Medvedieva N, Vershyhora V, Dubitska O, Shkurko T, Popovych L, Bondar O, Morozuk I, Onyshchenko S, Yevtushok L, Tsizh O, Bryl I, Tul O, Kalynka S, Zinkina I, Matviiuk S, Riabova Y, Gorovenko N. The analysis of using a panel of the most common variants in the PAH gene for the newborn screening in Ukraine. Mol Genet Metab Rep 2022; 32:100907. [PMID: 36046396 PMCID: PMC9421484 DOI: 10.1016/j.ymgmr.2022.100907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 07/26/2022] [Accepted: 07/26/2022] [Indexed: 11/25/2022] Open
Abstract
Phenylketonuria (PKU) is hyperphenylalaninemia that develops due to a deficiency of the phenylalanine hydroxylase enzyme (PAH). Identification of variants in the PAH gene is necessary for verification of the diagnosis, choice of treatment tactics, detection of heterozygous carriers. The aim of the study was to analyze the effectiveness of identification of selected pathological variants in the PAH gene during the newborn screening program. This study relied on the results of the examination of 257 patients (138 boys and 119 girls) with hyperphenylalaninemia from different regions of Ukraine. Genotyping was performed on nine pathogenic variants in PAH gene: I65T, R261Q, G272*, R252W, R261*, R408W, IVS12 + 1G > A, Y414C, IVS10-11G > A. According to the results of the study, variants R408W (AF = 52.7%), R252W (AF = 3.5%) and Y414C (AF = 1.8%) were the most common. More than half of the examined patients (51.7%) had a compound genotype with a major variant of R408W in one allele. Approximately a quarter of the examined patients (26.8%) had the R408W/R408W genotype. In 12.1% of patients, the applied panel of variants of the РАН gene did not allow us to identify the pathogenic variant in any allele. We conclude that the selected panel allowed us to identify the presence of variants in 87.9% of patients with PKU. The panel of genetic testing in the PAH gene for the newborns that we used for the study allows accurate prediction of some phenotypes for therapy planning. But in-depth analysis of pathological gene variants may be necessary for unclear and difficult cases of the disease, and for genetic counseling of patients families.
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Affiliation(s)
- Liliya Fishchuk
- SI "Reference-centre for molecular diagnostic of Public Health Ministry of Ukraine", Kyiv, Ukraine.,Institute of Genetic and Regenerative Medicine NAMS of Ukraine, Kyiv, Ukraine
| | - Zoia Rossokha
- SI "Reference-centre for molecular diagnostic of Public Health Ministry of Ukraine", Kyiv, Ukraine
| | - Natalia Olkhovich
- The National Children's Specialised Hospital "OHMATDYT", Kyiv, Ukraine
| | - Nataliia Pichkur
- The National Children's Specialised Hospital "OHMATDYT", Kyiv, Ukraine
| | - Olena Popova
- SI "Reference-centre for molecular diagnostic of Public Health Ministry of Ukraine", Kyiv, Ukraine
| | - Nataliia Medvedieva
- SI "Reference-centre for molecular diagnostic of Public Health Ministry of Ukraine", Kyiv, Ukraine
| | - Viktoriia Vershyhora
- SI "Reference-centre for molecular diagnostic of Public Health Ministry of Ukraine", Kyiv, Ukraine
| | - Olha Dubitska
- SI "Reference-centre for molecular diagnostic of Public Health Ministry of Ukraine", Kyiv, Ukraine
| | - Tetiana Shkurko
- The National Children's Specialised Hospital "OHMATDYT", Kyiv, Ukraine
| | | | - Olga Bondar
- Vinnitsa Regional Clinical Hospital, Vinnitsa, Ukraine
| | - Irina Morozuk
- Vinnitsa Regional Clinical Hospital, Vinnitsa, Ukraine
| | | | | | - Oksana Tsizh
- Rivne Regional Medical Diagnostic Center, Rivne, Ukraine
| | - Iryna Bryl
- ME "Regional Clinical Hospital for Rehabilitation and Diagnostics with Regional Centers for Family Planning and Human Reproduction, Medical Genetics", Poltava, Ukraine
| | - Olena Tul
- ME "Regional Clinical Hospital for Rehabilitation and Diagnostics with Regional Centers for Family Planning and Human Reproduction, Medical Genetics", Poltava, Ukraine
| | - Svitlana Kalynka
- Volyn Regional Children's Territorial Medical Center, Lutsk, Ukraine
| | - Iryna Zinkina
- Mykolaiv Regional Pediatric Hospital, Mykolaiv, Ukraine
| | | | | | - Nataliia Gorovenko
- Institute of Genetic and Regenerative Medicine NAMS of Ukraine, Kyiv, Ukraine.,Shupyk National Healthcare University of Ukraine, Kyiv, Ukraine
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4
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Molecular characterization of Thai patients with phenylalanine hydroxylase deficiency and in vitro functional study of two novel PAH variants. Mol Biol Rep 2021; 48:2063-2070. [PMID: 33677757 DOI: 10.1007/s11033-021-06163-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 01/15/2021] [Indexed: 10/22/2022]
Abstract
Phenylketonuria (PKU) is an autosomal recessive amino acid metabolism disorder caused by variants in the gene encoding phenylalanine hydroxylase (PAH; EC1.14.16.1). This study aimed to assess the specific heterogeneity of PAH variants found in Thai population as well as evaluate enzyme activity and expression of novel variants. PAH gene from 13 patients was analyzed by PCR amplification and direct Sanger-sequencing of 13 exons of the coding region. The novel variants were transiently transfected in COS-7 cells for functional verification. Eleven different PAH variants were identified: all pathogenic variants were missense variants, of which the most frequent variant was p.R169L, accounting for 24% (6/25) of all identified alleles. Two novel variants p.R169L and p.Y317N and previously reported variants with mutated residues at the same positions (p.R169H and p.Y317H) were expressed in COS-7 cells. These showed mildly impaired residual activity levels (42.3-63.1% of wild type), while the protein levels were well expressed (82.8-110%), except for p.R169L, which showed decreased protein expression of 55.7% compared to the wild type enzyme. All subjects with p.R169L identified in at least one of pathogenic alleles (one case is homozygous) had a metabolic phenotype of mild hyperphenylalaninemia (HPA). Our data has expanded the information on the genetic heterogeneity of Thai patients with PAH deficiency. This finding emphasizes the importance of genotyping in patients with HPA, and in vitro studies can provide additional information for prediction of phenotype.
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Ferreira F, Azevedo L, Neiva R, Sousa C, Fonseca H, Marcão A, Rocha H, Carmona C, Ramos S, Bandeira A, Martins E, Campos T, Rodrigues E, Garcia P, Diogo L, Ferreira AC, Sequeira S, Silva F, Rodrigues L, Gaspar A, Janeiro P, Amorim A, Vilarinho L. Phenylketonuria in Portugal: Genotype-phenotype correlations using molecular, biochemical, and haplotypic analyses. Mol Genet Genomic Med 2021; 9:e1559. [PMID: 33465300 PMCID: PMC8104178 DOI: 10.1002/mgg3.1559] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 10/29/2020] [Indexed: 11/12/2022] Open
Abstract
Background The impairment of the hepatic enzyme phenylalanine hydroxylase (PAH) causes elevation of phenylalanine levels in blood and other body fluids resulting in the most common inborn error of amino acid metabolism (phenylketonuria). Persistently high levels of phenylalanine lead to irreversible damage to the nervous system. Therefore, early diagnosis of the affected individuals is important, as it can prevent clinical manifestations of the disease. Methods In this report, the biochemical and genetic findings performed in 223 patients diagnosed through the Portuguese Neonatal Screening Program (PNSP) are presented. Results Overall, the results show that a high overlap exists between different types of variants and phenylalanine levels. Molecular analyses reveal a wide mutational spectrum in our population with a total of 56 previously reported variants, most of them found in compound heterozygosity (74% of the patients). Intragenic polymorphic markers were used to assess the haplotypic structure of mutated chromosomes for the most frequent variants found in homozygosity in our population (p.Ile65Thr, p.Arg158Gln, p.Leu249Phe, p.Arg261Gln, p.Val388Met, and c.1066‐11G>A). Conclusion Our data reveal high heterogeneity at the biochemical and molecular levels and are expected to provide a better understanding of the molecular basis of this disease and to provide clues to elucidate genotype–phenotype correlations.
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Affiliation(s)
- Filipa Ferreira
- Newborn Screening, Metabolic and Genetics Unit, Department of Human Genetics, National Institute of Health Dr Ricardo Jorge, Porto, Portugal
| | - Luísa Azevedo
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,IPATIMUP - Instituto de Patologia e Imunologia Molecular da Universidade do Porto, Porto, Portugal.,FCUP - Faculty of Sciences, University of Porto, Porto, Portugal
| | - Raquel Neiva
- Newborn Screening, Metabolic and Genetics Unit, Department of Human Genetics, National Institute of Health Dr Ricardo Jorge, Porto, Portugal
| | - Carmen Sousa
- Newborn Screening, Metabolic and Genetics Unit, Department of Human Genetics, National Institute of Health Dr Ricardo Jorge, Porto, Portugal
| | - Helena Fonseca
- Newborn Screening, Metabolic and Genetics Unit, Department of Human Genetics, National Institute of Health Dr Ricardo Jorge, Porto, Portugal
| | - Ana Marcão
- Newborn Screening, Metabolic and Genetics Unit, Department of Human Genetics, National Institute of Health Dr Ricardo Jorge, Porto, Portugal
| | - Hugo Rocha
- Newborn Screening, Metabolic and Genetics Unit, Department of Human Genetics, National Institute of Health Dr Ricardo Jorge, Porto, Portugal
| | - Célia Carmona
- Newborn Screening, Metabolic and Genetics Unit, Department of Human Genetics, National Institute of Health Dr Ricardo Jorge, Porto, Portugal
| | - Sónia Ramos
- Newborn Screening, Metabolic and Genetics Unit, Department of Human Genetics, National Institute of Health Dr Ricardo Jorge, Porto, Portugal
| | - Anabela Bandeira
- Inherited Metabolic Disease Reference Center, Pediatric Department, Centro Hospitalar Universitário do Porto, Porto, Portugal
| | - Esmeralda Martins
- Inherited Metabolic Disease Reference Center, Pediatric Department, Centro Hospitalar Universitário do Porto, Porto, Portugal
| | - Teresa Campos
- Metabolic Diseases Unit, Pediatric Department, University Center São João Hospital - HSJ, Porto, Portugal
| | - Esmeralda Rodrigues
- Metabolic Diseases Unit, Pediatric Department, University Center São João Hospital - HSJ, Porto, Portugal
| | - Paula Garcia
- Inherited Metabolic Disease Reference Center, Pediatric Hospital, Hospital and University Center of Coimbra, Coimbra, Portugal
| | - Luísa Diogo
- Inherited Metabolic Disease Reference Center, Pediatric Hospital, Hospital and University Center of Coimbra, Coimbra, Portugal
| | - Ana Cristina Ferreira
- Metabolic Unit, Hospital Dona Estefânia, Centro Hospitalar Universitário Lisboa Central, Lisbon, Portugal
| | - Silvia Sequeira
- Metabolic Unit, Hospital Dona Estefânia, Centro Hospitalar Universitário Lisboa Central, Lisbon, Portugal
| | - Francisco Silva
- Pediatric Department, Hospital Central of Funchal, Funchal, Portugal
| | - Luísa Rodrigues
- Pediatrics Department, Hospital of Divino Espírito Santo of Ponta Delgada, EPE, Ponta Delgada, Azores, Portugal
| | - Ana Gaspar
- Inherited Metabolic Disease Reference Center, Lisbon North University Hospital Center (CHULN), EPE, Lisboa, Portugal
| | - Patrícia Janeiro
- Inherited Metabolic Disease Reference Center, Lisbon North University Hospital Center (CHULN), EPE, Lisboa, Portugal
| | - António Amorim
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,IPATIMUP - Instituto de Patologia e Imunologia Molecular da Universidade do Porto, Porto, Portugal.,FCUP - Faculty of Sciences, University of Porto, Porto, Portugal
| | - Laura Vilarinho
- Newborn Screening, Metabolic and Genetics Unit, Department of Human Genetics, National Institute of Health Dr Ricardo Jorge, Porto, Portugal.,Research and Development Unit, Department of Human Genetics, National Institute of Health Dr Ricardo Jorge, Porto, Portugal
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6
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Hillert A, Anikster Y, Belanger-Quintana A, Burlina A, Burton BK, Carducci C, Chiesa AE, Christodoulou J, Đorđević M, Desviat LR, Eliyahu A, Evers RAF, Fajkusova L, Feillet F, Bonfim-Freitas PE, Giżewska M, Gundorova P, Karall D, Kneller K, Kutsev SI, Leuzzi V, Levy HL, Lichter-Konecki U, Muntau AC, Namour F, Oltarzewski M, Paras A, Perez B, Polak E, Polyakov AV, Porta F, Rohrbach M, Scholl-Bürgi S, Spécola N, Stojiljković M, Shen N, Santana-da Silva LC, Skouma A, van Spronsen F, Stoppioni V, Thöny B, Trefz FK, Vockley J, Yu Y, Zschocke J, Hoffmann GF, Garbade SF, Blau N. The Genetic Landscape and Epidemiology of Phenylketonuria. Am J Hum Genet 2020; 107:234-250. [PMID: 32668217 PMCID: PMC7413859 DOI: 10.1016/j.ajhg.2020.06.006] [Citation(s) in RCA: 121] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Accepted: 06/05/2020] [Indexed: 11/22/2022] Open
Abstract
Phenylketonuria (PKU), caused by variants in the phenylalanine hydroxylase (PAH) gene, is the most common autosomal-recessive Mendelian phenotype of amino acid metabolism. We estimated that globally 0.45 million individuals have PKU, with global prevalence 1:23,930 live births (range 1:4,500 [Italy]-1:125,000 [Japan]). Comparing genotypes and metabolic phenotypes from 16,092 affected subjects revealed differences in disease severity in 51 countries from 17 world regions, with the global phenotype distribution of 62% classic PKU, 22% mild PKU, and 16% mild hyperphenylalaninemia. A gradient in genotype and phenotype distribution exists across Europe, from classic PKU in the east to mild PKU in the southwest and mild hyperphenylalaninemia in the south. The c.1241A>G (p.Tyr414Cys)-associated genotype can be traced from Northern to Western Europe, from Sweden via Norway, to Denmark, to the Netherlands. The frequency of classic PKU increases from Europe (56%) via Middle East (71%) to Australia (80%). Of 758 PAH variants, c.1222C>T (p.Arg408Trp) (22.2%), c.1066-11G>A (IVS10-11G>A) (6.4%), and c.782G>A (p.Arg261Gln) (5.5%) were most common and responsible for two prevalent genotypes: p.[Arg408Trp];[Arg408Trp] (11.4%) and c.[1066-11G>A];[1066-11G>A] (2.6%). Most genotypes (73%) were compound heterozygous, 27% were homozygous, and 55% of 3,659 different genotypes occurred in only a single individual. PAH variants were scored using an allelic phenotype value and correlated with pre-treatment blood phenylalanine concentrations (n = 6,115) and tetrahydrobiopterin loading test results (n = 4,381), enabling prediction of both a genotype-based phenotype (88%) and tetrahydrobiopterin responsiveness (83%). This study shows that large genotype databases enable accurate phenotype prediction, allowing appropriate targeting of therapies to optimize clinical outcome.
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Affiliation(s)
- Alicia Hillert
- Division of Child Neurology and Metabolic Medicine, Centre for Child and Adolescent Medicine, Clinic I, University Hospital Heidelberg, 69120 Heidelberg, Germany
| | - Yair Anikster
- Metabolic Disease Unit, Edmond and Lily Safra Children's Hospital, Sheba Medical Center, Tel-Aviv University, 52621 Tel-Aviv, Israel
| | - Amaya Belanger-Quintana
- Unidad de Enfermedades Metabolicas, Servicio de Pediatria, Hospital Ramon y Cajal, 28034 Madrid, Spain
| | - Alberto Burlina
- Division of Inherited Metabolic Diseases, Department of Woman's and Child's Health, University Hospital, 35129 Padua, Italy
| | - Barbara K Burton
- Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL 60611, USA
| | - Carla Carducci
- Department of Experimental Medicine, Sapienza University of Rome, 00185 Rome, Italy
| | - Ana E Chiesa
- Fundación de Endocrinología Infantil (FEI), C1425 Buenos Aires, Argentina
| | - John Christodoulou
- Murdoch Children's Research Institute and Department of Pediatrics, University of Melbourne, Melbourne, VIC 3052, Australia
| | - Maja Đorđević
- Institute of Mother and Child Healthcare "Dr. Vukan Čupić," 11000 Belgrade, Serbia
| | - Lourdes R Desviat
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular CSIC-UAM, Universidad Autónoma de Madrid. CIBERER, IdiPAz, 28049 Madrid, Spain
| | - Aviva Eliyahu
- Metabolic Disease Unit, Edmond and Lily Safra Children's Hospital, Sheba Medical Center, Tel-Aviv University, 52621 Tel-Aviv, Israel
| | - Roeland A F Evers
- University of Groningen, University Medical Center Groningen, Beatrix Children's Hospital, Section of Metabolic Diseases, 9712 CP Groningen, the Netherlands
| | - Lena Fajkusova
- Centre of Molecular Biology and Gene Therapy, University Hospital Brno, 62500 Brno, Czech Republic
| | - François Feillet
- Reference Center for Inherited Metabolic Diseases, University Hospital of Nancy, 54511 Vandoeuvre-lès-Nancy, France
| | - Pedro E Bonfim-Freitas
- Laboratory of Inborn Errors of Metabolism, Institute of Biological Sciences, Federal University of Pará, Belém 66075-110, Brazil
| | - Maria Giżewska
- Department of Pediatrics, Endocrinology, Diabetology, Metabolic Diseases and Cardiology, Pomeranian Medical University, 71-252 Szczecin, Poland
| | | | - Daniela Karall
- Clinic of Pediatrics, Division of Inherited Metabolic Disorders, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Katya Kneller
- Metabolic Disease Unit, Edmond and Lily Safra Children's Hospital, Sheba Medical Center, Tel-Aviv University, 52621 Tel-Aviv, Israel
| | | | - Vincenzo Leuzzi
- Department of Human Neuroscience, Sapienza University of Rome, 00185 Rome, Italy
| | - Harvey L Levy
- Division of Genetics and Genomics, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | | | - Ania C Muntau
- University Children's Hospital, University Medical Center Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Fares Namour
- Reference Center for Inherited Metabolic Diseases, University Hospital of Nancy, 54511 Vandoeuvre-lès-Nancy, France
| | - Mariusz Oltarzewski
- Department of Screening and Metabolic Diagnostics, Institute of Mother and Child, 01-211 Warsaw, Poland
| | - Andrea Paras
- Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL 60611, USA
| | - Belen Perez
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular CSIC-UAM, Universidad Autónoma de Madrid. CIBERER, IdiPAz, 28049 Madrid, Spain
| | - Emil Polak
- Comenius University, Faculty of Natural Sciences, Department of Molecular Biology, 84215 Bratislava 4, Slovak Republic
| | | | - Francesco Porta
- Department of Pediatrics, AOU Citta' della Salute e della Scienza di Torino, 10126 Torino, Italy
| | - Marianne Rohrbach
- Division of Metabolism, University Children's Hospital, 8032 Zürich, Switzerland
| | - Sabine Scholl-Bürgi
- Clinic of Pediatrics, Division of Inherited Metabolic Disorders, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Norma Spécola
- Unidad de Metabolismo. Hospital de Niños "Sor Ludovica" de La Plata, 1904 Buenos Aires, Argentina
| | - Maja Stojiljković
- Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, 11000 Belgrade, Serbia
| | - Nan Shen
- Department of Infectious Diseases, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, 2000025 Shanghai, China
| | - Luiz C Santana-da Silva
- Laboratory of Inborn Errors of Metabolism, Institute of Biological Sciences, Federal University of Pará, Belém 66075-110, Brazil
| | | | - Francjan van Spronsen
- University of Groningen, University Medical Center Groningen, Beatrix Children's Hospital, Section of Metabolic Diseases, 9712 CP Groningen, the Netherlands
| | - Vera Stoppioni
- Centro Screening Neonatale Regione Marche, Azienda Ospedaliera Ospedali Riuniti Marche Nord, 61032 Fano, Italy
| | - Beat Thöny
- Division of Metabolism, University Children's Hospital, 8032 Zürich, Switzerland
| | - Friedrich K Trefz
- Division of Child Neurology and Metabolic Medicine, Centre for Child and Adolescent Medicine, Clinic I, University Hospital Heidelberg, 69120 Heidelberg, Germany
| | - Jerry Vockley
- UPMC, Children's Hospital of Pittsburgh, Pittsburgh, PA 15224, USA
| | - Youngguo Yu
- Department of Pediatric Endocrinology/Genetics, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Institute for Pediatric Research, 2000025 Shanghai, China
| | - Johannes Zschocke
- Institute of Human Genetics, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Georg F Hoffmann
- Division of Child Neurology and Metabolic Medicine, Centre for Child and Adolescent Medicine, Clinic I, University Hospital Heidelberg, 69120 Heidelberg, Germany
| | - Sven F Garbade
- Division of Child Neurology and Metabolic Medicine, Centre for Child and Adolescent Medicine, Clinic I, University Hospital Heidelberg, 69120 Heidelberg, Germany.
| | - Nenad Blau
- Division of Child Neurology and Metabolic Medicine, Centre for Child and Adolescent Medicine, Clinic I, University Hospital Heidelberg, 69120 Heidelberg, Germany; Division of Metabolism, University Children's Hospital, 8032 Zürich, Switzerland.
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7
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Esfahani MS, Vallian S. A comprehensive study of phenylalanine hydroxylase gene mutations in the Iranian phenylketonuria patients. Eur J Med Genet 2018; 62:103559. [PMID: 30389586 DOI: 10.1016/j.ejmg.2018.10.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 10/09/2018] [Accepted: 10/24/2018] [Indexed: 11/29/2022]
Abstract
Phenylketonuria (PKU) is a metabolic disorder caused by mutations in the phenylalanine hydroxylase (PAH) gene. After thalassemia, PKU is considered as the most common autosomal recessive diseases in the Iranian population. Therefore, an efficient diagnostic strategy is required to identify disease-causing mutations in this population. Following our first report in 2003, here we presented a comprehensive study on the mutation spectrum of the PAH gene in the Iranian population. This study was performed on 280 unrelated chromosomes from 140 Iranian patients with classic PKU. All 13 exons as well as exon-intron boundaries of the PAH gene were analyzed by direct DNA sequencing. Thirty four different mutations were identified by a mutation detection rate of 100%. IVS10-11G > A, p.P281L, R261Q, p.F39del and IVS11+1G > C were the most prevalent mutations with frequencies of 26.07%, 19.3%, 12.86%, 6.07 and 3.93%, respectively. All other mutations represented a relative frequency less than 3.5%. The data from this study provided a comprehensive spectrum of the PAH gene mutations which can facilitate carrier detection and prenatal diagnosis of PKU disease in the Iranian population.
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Affiliation(s)
| | - Sadeq Vallian
- Division of Genetics, Department of Biology, Faculty of Science, University of Isfahan, Isfahan, IR, Iran.
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8
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Himmelreich N, Shen N, Okun JG, Thiel C, Hoffmann GF, Blau N. Relationship between genotype, phenylalanine hydroxylase expression and in vitro activity and metabolic phenotype in phenylketonuria. Mol Genet Metab 2018; 125:86-95. [PMID: 30037505 DOI: 10.1016/j.ymgme.2018.06.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 06/21/2018] [Accepted: 06/22/2018] [Indexed: 01/22/2023]
Abstract
Residual phenylalanine hydroxylase (PAH) activity is the main determinant of the metabolic phenotype in phenylketonuria (PKU). The genotypic heterogeneity of PKU, involving >1000 PAH variants and over 2500 different genotypes, makes genotype-based phenotype prediction challenging. While a relationship between PAH variants and the metabolic phenotype is well established, we questioned the importance of PAH expression and residual in vitro activity for the metabolic phenotype. Thirty-four PAH variants (p.F39 L, p.A47V, p.D59Y, p.I65S, p.R68G, p.R68S, p.E76G, p.A104D, p.D143G, p.R155H, p.R176L, p.V190A, p.G218 V, p.R241C, p.R243Q, p.P244L, p.R252W, p.R261Q, p.E280K, p.R297H, p.A300S, p.I306V, p.A309V, p.L311P, p.A313T, p.L348 V, p.V388 M, A403V, p.R408Q, p.R408W, p.R413P, p.D415N, p.Y417H, and p.A434D) were transiently transfected into COS-7 cells, and expression of PAH was investigated. Expression patterns were compared with in vitro PAH activity and allelic phenotype values (APVs). In vitro PAH activity was significantly higher (p < .01) in variants associated with mild hyperphenylalaninemia (PAH activity = 52.1 ± 8.5%; APV = 6.7-10.0) than that in classic PKU variants (PAH activity = 21.1 ± 7.0%; APV = 0-2.7). Mild PKU variants (PAH activity = 40.2 ± 7.6%; APV = 2.8-6.6) were not significantly different from mild hyperphenylalaninemia, but there was a difference (p < .048) compared with classic PKU phenotypes.
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Affiliation(s)
- Nastassja Himmelreich
- Center for Child and Adolescent Medicine, and Dietmar-Hopp Metabolic Center, University of Heidelberg, Heidelberg, Germany
| | - Nan Shen
- Center for Child and Adolescent Medicine, and Dietmar-Hopp Metabolic Center, University of Heidelberg, Heidelberg, Germany; Department of Rehabilitation Medicine, Xin Hua Hospital affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jürgen G Okun
- Center for Child and Adolescent Medicine, and Dietmar-Hopp Metabolic Center, University of Heidelberg, Heidelberg, Germany
| | - Christian Thiel
- Center for Child and Adolescent Medicine, and Dietmar-Hopp Metabolic Center, University of Heidelberg, Heidelberg, Germany
| | - Georg F Hoffmann
- Center for Child and Adolescent Medicine, and Dietmar-Hopp Metabolic Center, University of Heidelberg, Heidelberg, Germany
| | - Nenad Blau
- Center for Child and Adolescent Medicine, and Dietmar-Hopp Metabolic Center, University of Heidelberg, Heidelberg, Germany.
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9
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Li N, He C, Li J, Tao J, Liu Z, Zhang C, Yuan Y, Jiang H, Zhu J, Deng Y, Guo Y, Li Q, Yu P, Wang Y. Analysis of the genotype-phenotype correlation in patients with phenylketonuria in mainland China. Sci Rep 2018; 8:11251. [PMID: 30050108 PMCID: PMC6062512 DOI: 10.1038/s41598-018-29640-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 07/13/2018] [Indexed: 11/22/2022] Open
Abstract
Mutations in the gene encoding phenylalanine hydroxylase (PAH) are associated with various degrees of phenylketonuria (PKU). The aim of our study was to define the genotype-phenotype correlations of mutations in the PAH gene that cause phenylketonuria (PKU) among the Chinese mainland population. Mutations in the PAH gene were analysed by next-generation sequencing, and a genotype-phenotype correlation analysis was performed in 1079 patients. Fifteen “null + null” genotypes, including four homoallelic and eleven heteroallelic genotypes, were clearly associated with classic PKU. Five functionally hemizygous (p.E280K, p.R252Q, p.E56D, p.S310F and p.T372R) and four compound heterozygous (p.T278I/p.S359L, p.R408W/p.R243Q, p.F161S/p.R243Q and p.F161S/p.R413P) genotypes were clearly associated with classic PKU. Ten functionally hemizygous genotypes, p.G257V, p.R158W, p.L255S, p.G247V, p.F161S, p.R158Q, p.V388M, p.I65T, p.I324N and p.R400K, were frequently associated with classic PKU. Three functionally hemizygous genotypes, p.P147L, p.I95del and p.F331S, and four compound heterozygous genotypes, p.G257V/p.R408Q, p.A434D/p.R413P, p.R243Q/p.A47E and p.R241C/p.G239D, were consistently correlated with mild PKU. Three functionally hemizygous genotypes, p.H107R, p.Q419R and p.F392I, and nine compound heterozygous genotypes (p.G312V/p.R241C, p.R243Q/p.V230I, p.R243Q/p.A403V, p.R243Q/p.Q419R, p.R243Q/p.R53H, p.R243Q/p.H107R, p.R241C/p.R408Q, p.R241C/p.H220P and p.R53H/p.R400K) were consistent with mild hyperphenylalaninaemia (MHP). Our study provides further support for the hypothesis that the PAH genotype is the main factor that determines the phenotype of PKU.
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Affiliation(s)
- Nana Li
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Chunhua He
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Jing Li
- Laboratory of Translational Medicine, Chinese PLA General Hospital, Beijing, China
| | - Jing Tao
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Zhen Liu
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Chunyan Zhang
- Laboratory of Translational Medicine, Chinese PLA General Hospital, Beijing, China
| | - Yuan Yuan
- Tianjin Medical Laboratory, BGI-Tianjin, BGI-Shenzhen, Tianjin, 300308, China
| | - Hui Jiang
- BGI-Shenzhen, Shenzhen, 518103, China.,China National GeneBank, BGI-Shenzhen, Shenzhen, 518120, China
| | - Jun Zhu
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Ying Deng
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Yixiong Guo
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Qintong Li
- Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Ping Yu
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China. .,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China.
| | - Yanping Wang
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China. .,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China.
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10
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Structural features of the regulatory ACT domain of phenylalanine hydroxylase. PLoS One 2013; 8:e79482. [PMID: 24244510 PMCID: PMC3828330 DOI: 10.1371/journal.pone.0079482] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Accepted: 09/22/2013] [Indexed: 11/30/2022] Open
Abstract
Phenylalanine hydroxylase (PAH) catalyzes the conversion of L-Phe to L-Tyr. Defects in PAH activity, caused by mutations in the human gene, result in the autosomal recessively inherited disease hyperphenylalaninemia. PAH activity is regulated by multiple factors, including phosphorylation and ligand binding. In particular, PAH displays positive cooperativity for L-Phe, which is proposed to bind the enzyme on an allosteric site in the N-terminal regulatory domain (RD), also classified as an ACT domain. This domain is found in several proteins and is able to bind amino acids. We used molecular dynamics simulations to obtain dynamical and structural insights into the isolated RD of PAH. Here we show that the principal motions involve conformational changes leading from an initial open to a final closed domain structure. The global intrinsic motions of the RD are correlated with exposure to solvent of a hydrophobic surface, which corresponds to the ligand binding-site of the ACT domain. Our results strongly suggest a relationship between the Phe-binding function and the overall dynamic behaviour of the enzyme. This relationship may be affected by structure-disturbing mutations. To elucidate the functional implications of the mutations, we investigated the structural effects on the dynamics of the human RD PAH induced by six missense hyperphenylalaninemia-causing mutations, namely p.G46S, p.F39C, p.F39L, p.I65S, p.I65T and p.I65V. These studies showed that the alterations in RD hydrophobic interactions induced by missense mutations could affect the functionality of the whole enzyme.
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11
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Mutation spectrum of phenylketonuria in Syrian population: Genotype–phenotype correlation. Gene 2013; 528:241-7. [DOI: 10.1016/j.gene.2013.07.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 06/24/2013] [Accepted: 07/01/2013] [Indexed: 11/24/2022]
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12
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Shi Z, Sellers J, Moult J. Protein stability and in vivo concentration of missense mutations in phenylalanine hydroxylase. Proteins 2011; 80:61-70. [PMID: 21953985 DOI: 10.1002/prot.23159] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Revised: 07/21/2011] [Accepted: 07/26/2011] [Indexed: 11/07/2022]
Abstract
A previous computational analysis of missense mutations linked to monogenic disease found a high proportion of missense mutations affect protein stability, rather than other aspects of protein structure and function. The purpose of this study is to relate the presence of such stability damaging missense mutations to the levels of a particular protein present under "in vivo" like conditions, and to test the reliability of the computational methods. Experimental data on a set of missense mutations of the enzyme phenylalanine hydroxylase (PAH) associated with the monogenic disease phenylketonuria (PKU) have been compared with the expected in vivo impact on protein function, obtained using SNPs3D, an in silico analysis package. A high proportion of the PAH mutations are predicted to be destabilizing. The overall agreement between predicted stability impact and experimental evidence for lower protein levels is in accordance with the estimated error rates of the methods. For these mutations, destabilization of protein three-dimensional structure is the major molecular mechanism leading to PKU, and results in a substantial reduction of in vivo PAH protein concentration. Although of limited scale, the results support the view that destabilization is the most common mechanism by which missense mutations cause monogenic disease. In turn, this conclusion suggests the general therapeutic strategy of developing drugs targeted at restoring wild type stability.
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Affiliation(s)
- Zhen Shi
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland 20850, USA
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13
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Zaffanello M, Zamboni G, Maselli M, Gandini A, Camilot M, Maffeis C, Burlina AB, Tatò L. Genetic analysis carried out on blood-spots of phenylalanine hydroxylase-deficient newborns detected by northeastern Italian neonatal screening. ACTA ACUST UNITED AC 2005; 9:133-7. [PMID: 15943553 DOI: 10.1089/gte.2005.9.133] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The aim of this work was to perform genetic analysis on 18 different blood-spot samples collected from neonates detected as hyperphenylalaninemic by Northeastern Italian screening program. DNA was extracted from blood-spots. Exons/introns of PAH gene were amplified by polymerase chain reaction (PCR), and PCR products were purified and sequenced with both forward and reverse primers. The most frequent mutations were IVS12nt1g>a (16.7%) and R408W, P281L and L48S (all together 11.1%). As expected, compound heterozygosity was the usual finding; homozygosity was found only in two patients with R158Q and IVS2nt5g>c mutations. The V230I mutation was reported for the first time in Italy. We found six previously described polymorphisms (V245V, IVS4nt47c>t, IVS2nt19t>c, IVS3nt-22c>t, IVS5nt-54a>g, and E280>Q280). To our knowledge, four genotypes were not previously described: R158Q/V230I present in one patient with classical PKU; and L48S/R408Q, A403V/IVS2nt-13t>g, and G272X/V230I present in patients showing HPA phenotype. Most of the mutations were located in the exons 12 and 7 and in exon/intron 2 (83.3% detection of total mutations in PKU or HPA patients of Northeastern Italy). From a practical viewpoint, the genetic analysis of blood-spots collected on Guthrie cards for neonatal screening for PKU could be a simple method to establish the genotype of neonates. Consequently, the genotype/phenotype correlation could lead to a more accurate diagnosis and prognosis for families.
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Affiliation(s)
- M Zaffanello
- Department of Paediatrics, University of Verona, 37134 Verona, Italy.
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14
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Vallian S, Barahimi E, Moeini H. Phenylketonuria in Iranian population: a study in institutions for mentally retarded in Isfahan. Mutat Res 2003; 526:45-52. [PMID: 12714182 DOI: 10.1016/s0027-5107(03)00015-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Phenylalanine hydroxylase (PAH) deficiency is caused by mutations in the PAH gene (12q22-q24) resulting in a primary deficiency of the PAH enzyme activity, intolerance to the dietary intake of phenylalanine (Phe) and production of the phenylketonuria (PKU) disease. To date there have been no reports on the molecular analysis of PKU in Iranian population. In this study, the states of the PKU disease in terms of prevalence and mutation spectrum among patients reside in the institutions for mentally retarded in Isfahan was investigated. In the first step, 611 out of 1541 patients with PKU phenotype or severe mental retardation were screened for the PKU disease using the Guthrie bacterial inhibition assay (GBIA) followed by HPLC. Among the patients screened 34 (5.56%) were found positive with abnormal serum Phe of above 7mg/dl. In the next step, the presence of 18 common mutations of the PAH gene in 26 of the patients with classical PKU (serum Phe above 20mg/dl) was investigated, using the polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). Of the 52 independent mutant alleles that were analyzed, 34 (65.38%) were genotyped showing 8 mutations as follows: R252W (15.38%), Q232Q (13.46%), R261Q (7.69%), delL364 (7.69%), IVS10-11g>a (5.77%), L333F (5.77%), V245V (5.77%) and S67P (3.85%). The results from this study may serve as a reference to analyze the PKU mutations in other part of Iran, and to establish diagnostic tests for carrier detection and prenatal diagnosis of the PKU disease in Iranian population.
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Affiliation(s)
- Sadeq Vallian
- Department of Biology, Faculty of Science, Division of Genetics, Isfahan University, Hezarjerib Street, Iran.
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15
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Andersen OA, Flatmark T, Hough E. Crystal structure of the ternary complex of the catalytic domain of human phenylalanine hydroxylase with tetrahydrobiopterin and 3-(2-thienyl)-L-alanine, and its implications for the mechanism of catalysis and substrate activation. J Mol Biol 2002; 320:1095-108. [PMID: 12126628 DOI: 10.1016/s0022-2836(02)00560-0] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Phenylalanine hydroxylase catalyzes the stereospecific hydroxylation of L-phenylalanine, the committed step in the degradation of this amino acid. We have solved the crystal structure of the ternary complex (hPheOH-Fe(II).BH(4).THA) of the catalytically active Fe(II) form of a truncated form (DeltaN1-102/DeltaC428-452) of human phenylalanine hydroxylase (hPheOH), using the catalytically active reduced cofactor 6(R)-L-erythro-5,6,7,8-tetrahydrobiopterin (BH(4)) and 3-(2-thienyl)-L-alanine (THA) as a substrate analogue. The analogue is bound in the second coordination sphere of the catalytic iron atom with the thiophene ring stacking against the imidazole group of His285 (average interplanar distance 3.8A) and with a network of hydrogen bonds and hydrophobic contacts. Binding of the analogue to the binary complex hPheOH-Fe(II).BH(4) triggers structural changes throughout the entire molecule, which adopts a slightly more compact structure. The largest change occurs in the loop region comprising residues 131-155, where the maximum r.m.s. displacement (9.6A) is at Tyr138. This loop is refolded, bringing the hydroxyl oxygen atom of Tyr138 18.5A closer to the iron atom and into the active site. The iron geometry is highly distorted square pyramidal, and Glu330 adopts a conformation different from that observed in the hPheOH-Fe(II).BH(4) structure, with bidentate iron coordination. BH(4) binds in the second coordination sphere of the catalytic iron atom, and is displaced 2.6A in the direction of Glu286 and the iron atom, relative to the hPheOH-Fe(II).BH(4) structure, thus changing its hydrogen bonding network. The active-site structure of the ternary complex gives new insight into the substrate specificity of the enzyme, notably the low affinity for L-tyrosine. Furthermore, the structure has implications both for the catalytic mechanism and the molecular basis for the activation of the full-length tetrameric enzyme by its substrate. The large conformational change, moving Tyr138 from a surface position into the active site, may reflect a possible functional role for this residue.
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16
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Erlandsen H, Stevens RC. A structural hypothesis for BH4 responsiveness in patients with mild forms of hyperphenylalaninaemia and phenylketonuria. J Inherit Metab Dis 2001; 24:213-30. [PMID: 11405341 DOI: 10.1023/a:1010371002631] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Deficiencies in the human enzyme phenylalanine hydroxylase (PAH) due to mutations in the PAH gene (PAH) result in the inborn error of metabolism phenylketonuria (PKU). The clinical symptom of this disease is an elevated concentration of L-phenylalanine (L-Phe) in blood serum. To prevent mental retardation due to the buildup of neurotoxic metabolites of L-Phe, patients with severe PKU must be treated with a low-L-Phe diet starting early in their life. Owing to extensive newborn screening programmes and genotyping efforts, more than 400 different mutations have been identified in the PAH gene. Recently, there have been several reports of PKU patients showing a normalization of their L-Phe concentrations upon oral administration of the natural cofactor to PAH, (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin (BH4). In an attempt to correlate the clinical responsiveness to BH4 administration with PKU genotype, we propose specific structural consequences for this subset of PAH mutations. Based on the location and proximity of this subset of mutations to the cofactor-binding site in the three-dimensional structure of PAH, a hypothesis for BH4 responsiveness in PKU patients is presented. It is believed that some of these mutations result in expressed mutant enzymes that are Km variants (with a lower binding affinity for BH4) of the standard PAH enzyme phenotype. Oral administration of excess BH4 thus makes it possible for these mutant enzymes to suppress their low binding affinity for BH4, enabling this subset of PAH mutations to perform the L-Phe hydroxylation reaction. Most of the BH4-responsive PAH mutations map to the catalytic domain of PAH in either of two categories. Residues are located in cofactor-binding regions or in regions that interact with the secondary structural elements involved in cofactor binding. Based on the series of known mutations that have been found to be responsive to BH4, we propose that other subsets of PAH mutations will have a high likelihood of being responsive to oral BH4 administration.
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Affiliation(s)
- H Erlandsen
- The Scripps Research Institute, Department of Molecular Biology and Institute for Childhood and Neglected Diseases, La Jolla, CA 92037, USA.
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17
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Sueoka H, Nagao M, Chiba S. Rapid mutation screening of phenylketonuria by polymerase chain reaction-linked restriction enzyme assay and direct sequence of the phenylalanine hydroxylase gene: clinical application in northern Japan and northern China. GENETIC TESTING 2001; 4:249-56. [PMID: 11142755 DOI: 10.1089/10906570050501461] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We describe a simple and technically feasible method for mutation screening of the phenylalanine hydroxylase (PAH) gene and its application to Japanese and Chinese patients with hyperphenylalaninemia. The strategy is based on the identification of a nucleotide substitution by restriction enzyme analysis, coupled with PCR and direct sequencing of exon 7 of the PAH gene. Because the detection of various mutations can proceed simultaneously using the same technique, it is quite rapid and reproducible, making it possible to perform effective molecular diagnosis and carrier screening in most laboratories. Using this procedure, we found that the most common molecular defects were R413P in Hokkaido, Japan (35 %) and R243Q in Heilongjiang, China (50%). R111X, IVS4nt-1, and five mutations in exon 7 (R241C, R243Q, R252W, A259T, and S273P) accounted for 55% of phenylketonuria (PKU) alleles in Hokkaido. In Heilongjiang, the R111X, Y356X, and R408W mutations accounted for 35% of PKU alleles. Clinically, homozygotes or compound heterozygotes of null alleles, which express nonfunctional enzyme activity, were all associated with classic PKU. On the other hand, patients heterozygous for the R241C allele had a benign phenotype of mild hyperphenylalaninemia. The DNA diagnosis in early infancy can predict various PKU phenotypes, and can prove useful in decision-making concerning dietary therapy.
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Affiliation(s)
- H Sueoka
- Department of Pediatrics, National Otaru Hospital, Japan
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18
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Romano V, Lio D, Calì F, Scola L, Leggio L, D'Anna C, DeLeo G, Salermo A. A methodological strategy for PAH genotyping in populations with a marked molecular heterogeneity of hyperphenylalaninemia. Mol Cell Probes 2001; 15:13-9. [PMID: 11284432 DOI: 10.1006/mcpr.2000.0330] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The elucidation of the molecular basis of hyperphenylalaninemia in various world populations (PKU Consortium Database: http://www.mcgill/ca/pahdb/) has revealed a remarkable molecular heterogeneity at the locus encoding for phenylalanine hydroxylase. As a consequence, genotyping of HPA patients has prompted the establishment of an impressive number of mutatIon detection protocols. In spite of the large variety of methods proposed so far, no comprehensive strategy has been yet developed for the detection of PAH gene mutations. Therefore, new approaches, combining the advantages of individual methods are required, especially in populations with a high number of PAH gene mutations. In this study, we propose the use of Reverse Dot Blot Analysis within a general mutation protocol to simplify the genotyping of hyperphenylalaninemics in the very heterogeneous population of Sicily (Italy).
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Affiliation(s)
- V Romano
- Diaprtimento de Biopatologia e metodologie Biomediche, Università di Palermo, Palermo, Italy.
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19
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Waters PJ, Parniak MA, Nowacki P, Scriver CR. In vitro expression analysis of mutations in phenylalanine hydroxylase: linking genotype to phenotype and structure to function. Hum Mutat 2000; 11:4-17. [PMID: 9450897 DOI: 10.1002/(sici)1098-1004(1998)11:1<4::aid-humu2>3.0.co;2-l] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Mutations in the human phenylalanine hydroxylase gene (PAH) altering the expressed cDNA nucleotide sequence (GenBank U49897) can impair activity of the corresponding enzyme product (hepatic phenylalanine hydroxylase, PAH) and cause hyperphenylalaninemia (HPA), a metabolic phenotype for which the major disease form is phenylketonuria (PKU; OMIM 261600). In vitro expression analysis of inherited human mutations in eukaryotic, prokaryotic, and cell-free systems is informative about the mechanisms of mutation effects on enzymatic activity and their predicted effect on the metabolic phenotype. Corresponding analysis of site-directed mutations in rat Pah cDNA has assigned critical functional roles to individual amino acid residues within the best understood species of phenylalanine hydroxylase. Data on in vitro expression of 35 inherited human mutations and 22 created rat mutations are reviewed here. The core data are accessible at the PAH Mutation Analysis Consortium Web site (http://www.mcgill.ca/pahdb).
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Affiliation(s)
- P J Waters
- Department of Pediatrics, McGill University, Montreal, Quebec, Canada
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Abstract
The human phenylalanine hydroxylase gene (PAH) (locus on human chromosome 12q24.1) contains the expressed nucleotide sequence which encodes the hepatic enzyme phenylalanine hydroxylase (PheOH). The PheOH enzyme hydroxylates the essential amino acid l-phenylalanine resulting in another amino acid, tyrosine. This is the major pathway for catabolizing dietary l-phenylalanine and accounts for approximately 75% of the disposal of this amino acid. The autosomal recessive disease phenylketonuria (PKU) is the result of a deficiency of PheOH enzymatic activity due to mutations in the PAH gene. Of the mutant alleles that cause hyperphenylalaninemia or PKU 99% map to the PAH gene. The remaining 1% maps to several genes that encode enzymes involved in the biosynthesis or regeneration of the cofactor ((6R)-l-erythro-5,6,7,8-tetrahydrobiopterin) regenerating the cofactor (tetrahydrobiopterin) necessary for the hydroxylation reaction. The recently solved crystal structures of human phenylalanine hydroxylase provide a structural scaffold for explaining the effects of some of the mutations in the PAH gene and suggest future biochemical studies that may increase our understanding of the PKU mutations.
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Affiliation(s)
- H Erlandsen
- Department of Molecular Biology and Institute for Childhood and Neglected Diseases, The Scripps Research Institute, La Jolla, California, 92037, USA
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21
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Bénit P, Rey F, Blandin-Savoja F, Munnich A, Abadie V, Rey J. The mutant genotype is the main determinant of the metabolic phenotype in phenylalanine hydroxylase deficiency. Mol Genet Metab 1999; 68:43-7. [PMID: 10479481 DOI: 10.1006/mgme.1999.2886] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Phenylketonuria and mild hyperphenylalaninemias are allelic disorders caused by mutations in the phenylalanine hydroxylase (PAH) gene. Following identification of the disease-causing mutation in 11 PAH-deficient patients, we tested the activity of the mutant gene products in an eukaryotic expression system. Two mutations markedly reduced PAH activity (A259V and L333F), one mutation mildly altered the enzyme activity (E390G), while the majority of mutant genotypes reduced the in vitro expression of PAH activity to 15-30% of controls. Comparing the predicted residual activity derived from expression studies to the clinical phenotypes of our PAH-deficient patients, we found that homozygosity for the L333F and E390G mutations resulted in severe and mild PAH deficiencies, respectively, both in vivo and in vitro, while compound heterozygosity (L333F/E390G) resulted in an intermediate dietary tolerance. Similarly, in vitro expression studies largely predicted dietary tolerance in compound heterozygotes for the A259V/IVS12nt1 (typical PKU), A259V/A403V, G218V/I65T, and G218V/R158Q mutations (mild variants). Taken together, these results support the view that expression studies are useful in predicting residual enzyme activity and that the mutant genotype at the PAH locus is the major determinant of metabolic phenotype in hyperphenylalaninemias.
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Affiliation(s)
- P Bénit
- Department of Genetics and Unité de Recherches sur les Handicaps Génétiques de l'Enfant, INSERM U-393, Hôpital des Enfants-Malades, 149 rue de Sèvres, Paris Cedex 15, 75743, France
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22
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Flatmark T, Stevens RC. Structural Insight into the Aromatic Amino Acid Hydroxylases and Their Disease-Related Mutant Forms. Chem Rev 1999; 99:2137-2160. [PMID: 11849022 DOI: 10.1021/cr980450y] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Torgeir Flatmark
- Department of Molecular Biology, Institute for Childhood and Neglected Diseases, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037
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23
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Fusetti F, Erlandsen H, Flatmark T, Stevens RC. Structure of tetrameric human phenylalanine hydroxylase and its implications for phenylketonuria. J Biol Chem 1998; 273:16962-7. [PMID: 9642259 DOI: 10.1074/jbc.273.27.16962] [Citation(s) in RCA: 126] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phenylalanine hydroxylase (PheOH) catalyzes the conversion of L-phenylalanine to L-tyrosine, the rate-limiting step in the oxidative degradation of phenylalanine. Mutations in the human PheOH gene cause phenylketonuria, a common autosomal recessive metabolic disorder that in untreated patients often results in varying degrees of mental retardation. We have determined the crystal structure of human PheOH (residues 118-452). The enzyme crystallizes as a tetramer with each monomer consisting of a catalytic and a tetramerization domain. The tetramerization domain is characterized by the presence of a domain swapping arm that interacts with the other monomers forming an antiparallel coiled-coil. The structure is the first report of a tetrameric PheOH and displays an overall architecture similar to that of the functionally related tyrosine hydroxylase. In contrast to the tyrosine hydroxylase tetramer structure, a very pronounced asymmetry is observed in the phenylalanine hydroxylase, caused by the occurrence of two alternate conformations in the hinge region that leads to the coiled-coil helix. Examination of the mutations causing PKU shows that some of the most frequent mutations are located at the interface of the catalytic and tetramerization domains. Their effects on the structural and cellular stability of the enzyme are discussed.
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Affiliation(s)
- F Fusetti
- Department of Chemistry, University of California and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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24
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Rivera I, Leandro P, Lichter-Konecki U, Tavares de Almeida I, Lechner MC. Population genetics of hyperphenylalaninaemia resulting from phenylalanine hydroxylase deficiency in Portugal. J Med Genet 1998; 35:301-4. [PMID: 9598724 PMCID: PMC1051278 DOI: 10.1136/jmg.35.4.301] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
In order to elucidate the molecular basis of phenylketonuria (PKU) in Portugal, a detailed study of the Portuguese mutant phenylalanine hydroxylase (PAH) genes was performed. A total of 222 mutant alleles from 111 PKU families were analysed for 26 mutations and restriction fragment length polymorphismlvariable number tandem repeat (RFLP/VNTR) haplotypes. It was possible to characterise 55% of the mutant alleles, in which 14 different mutations (R261Q, V388M, IVS10nt-11, I65T, P281L, R252W, R158Q, L348V, Y414C, L311P, Y198fsdel22bp, R408W, R270K, and R261X) and three polymorphisms (Q232Q, V245V, and L385L) were identified. A total of 14 different haplotypes were observed, with a high prevalence of haplotype 1 among mutant and normal alleles. The results reported in this study show considerable genetic heterogeneity in the Portuguese PKU population, as has also been described for other southern European populations.
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Affiliation(s)
- I Rivera
- Centro de Patogénese Molecular, Faculdade de Farmácia da UL, Lisboa, Portugal
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25
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Erlandsen H, Fusetti F, Martinez A, Hough E, Flatmark T, Stevens RC. Crystal structure of the catalytic domain of human phenylalanine hydroxylase reveals the structural basis for phenylketonuria. NATURE STRUCTURAL BIOLOGY 1997; 4:995-1000. [PMID: 9406548 DOI: 10.1038/nsb1297-995] [Citation(s) in RCA: 146] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The 2.0 A crystal structure of the catalytic domain of human phenylalanine hydroxylase reveals a fold similar to that of tyrosine hydroxylase. It provides the first structural view of where mutations occur and a rationale to explain molecular mechanisms of the enzymatic phenotypes in the autosomal recessive disorder phenylketoneuria.
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26
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Kayaalp E, Treacy E, Waters PJ, Byck S, Nowacki P, Scriver CR. Human phenylalanine hydroxylase mutations and hyperphenylalaninemia phenotypes: a metanalysis of genotype-phenotype correlations. Am J Hum Genet 1997; 61:1309-17. [PMID: 9399896 PMCID: PMC1716084 DOI: 10.1086/301638] [Citation(s) in RCA: 142] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We analyzed correlations between mutant genotypes at the human phenylalanine hydroxylase locus (gene symbol PAH) and the corresponding hyperphenylalaninemia (HPA) phenotypes (notably, phenylketonuria [OMIM 261600]). We used reports, both published and in the PAH Mutation Analysis Consortium Database, on 365 patients harboring 73 different PAH mutations in 161 different genotypes. HPA phenotypes were classified as phenylketonuria (PKU), variant PKU, and non-PKU HPA. By analysis both of homoallelic mutant genotypes and of "functionally hemizygous" heteroallelic genotypes, we characterized the phenotypic effect of 48 of the 73 different, largely missense mutations. Among those with consistent in vivo expression, 24 caused PKU, 3 caused variant PKU, and 10 caused non-PKU HPA. However, 11 mutations were inconsistent in their effect: 9 appeared in two different phenotype classes, and 2 (I65T and Y414C) appeared in all three classes. Seven mutations were inconsistent in phenotypic effect when in vitro (unit-protein) expression was compared with the corresponding in vivo phenotype (an emergent property). We conclude that the majority of PAH mutations confer a consistent phenotype and that this is concordant with their effects, when known, predicted from in vitro expression analysis. However, significant inconsistencies, both between in vitro and in vivo phenotypes and between different individuals with similar PAH genotypes, reveal that the HPA-phenotype is more complex than that predicted by Mendelian inheritance of alleles at the PAH locus.
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Affiliation(s)
- E Kayaalp
- DeBelle Laboratory, McGill University-Montreal Children's Hospital Research Institute, Quebec, Canada
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27
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Eiken HG, Knappskog PM, Apold J, Flatmark T. PKU mutation G46S is associated with increased aggregation and degradation of the phenylalanine hydroxylase enzyme. Hum Mutat 1996; 7:228-38. [PMID: 8829656 DOI: 10.1002/(sici)1098-1004(1996)7:3<228::aid-humu7>3.0.co;2-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The G46S mutation in the phenylalanine hydroxylase (PAH) gene was identified by fluorescence-based single-strand conformation polymorphism (F-SSCP) analysis on phenylketonuria (PKU) haplotype 5.9 alleles. DNA sequencing of PAH exon 2 revealed a G-to-A transition in cDNA position 136. G46S mutations were present on 17 of 236 Norwegian PKU alleles (7.2%) and on 8 of 176 Swedish PKU alleles (4.5%). Analysis of all 13 exons with the flanking regions further detected a 1316-35c > t polymorphism (PAH intron 12), associated with both G46S and haplotype 5.9. Three patients were homozygous for the G46S mutation, two were untreated and had mild and severe mental retardation, respectively. The G46S mutation was introduced in the PAH cDNA by site-directed mutagenesis and expressed in three different systems (the pMAL/Escherichia coli system, the pcDNA3/human embryonic kidney (A293) cells, and the pcDNA3/TnT coupled in vitro transcription-translation system). The mutant recombinant E. coli fusion protein was recovered in high yield and with a specific activity of the purified tetrameric form, which was higher than the wild-type activity. After transient expression in A293 cells, the amount of the G46S protein was only about 3% of the wild type at equal PAH mRNA levels. The fusion protein cleaved by restriction protease factor Xa, as well as the enzyme produced by in vitro transcription-translation, revealed an abnormal susceptibility to form catalytically inactive high-molecular-mass aggregates of the enzyme. This aggregation, followed by an increased cellular degradation of the G46S mutant enzyme, is compatible with the clinical/metabolic phenotype of the affected homozygous and compound heterozygous patients.
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Affiliation(s)
- H G Eiken
- Department of Medical Genetics, Haukeland Hospital, University of Bergen, Norway
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28
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Eisensmith RC, Woo SL. Molecular genetics of phenylketonuria: from molecular anthropology to gene therapy. ADVANCES IN GENETICS 1995; 32:199-271. [PMID: 7741023 DOI: 10.1016/s0065-2660(08)60206-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- R C Eisensmith
- Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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29
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Guldberg P, Güttler F. Mutations in the phenylalanine hydroxylase gene: methods for their characterization. ACTA PAEDIATRICA (OSLO, NORWAY : 1992). SUPPLEMENT 1994; 407:27-33. [PMID: 7766950 DOI: 10.1111/j.1651-2227.1994.tb13443.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Mutations in the phenylalanine hydroxylase (PAH) gene represent the root cause of PAH-deficient hyperphenylalaninemia. To date, more than 160 different mutations have been reported. Single-base substitutions and microdeletions account for the majority of molecular defects. This review provides a brief general introduction to various strategies for detection of PAH mutations, and summarizes our own methodological developments. We have established a method based on PCR in combination with denaturing gradient gel electrophoresis (DGGE) for mutation scanning of the entire coding sequence and all exon/intron boundaries of the PAH. Systematic application of this method to the study of a large number of mutant chromosomes from hyperphenylalaninemic patients demonstrated a 98% diagnostic efficiency and a 100% mutation detection efficiency. We have created compromised PCR and DGGE conditions for simultaneous amplification and simultaneous mutation scanning of all PAH-coding fragments. This technique is convenient in a diagnostic setting and allows "same-day" DNA-based diagnosis of newborns with hyperphenylalaninemia. A further modification of the method allows unambiguous identification of known mutations, circumventing the cumbersome step of nucleotide sequencing.
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Affiliation(s)
- P Guldberg
- Danish Center for Human Genome Research, John F Kennedy Institute, Glostrup
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30
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Kalanin J, Takarada Y, Kagawa S, Yamashita K, Ohtsuka N, Matsuoka A. Gypsy phenylketonuria: a point mutation of the phenylalanine hydroxylase gene in Gypsy families from Slovakia. AMERICAN JOURNAL OF MEDICAL GENETICS 1994; 49:235-9. [PMID: 8116675 DOI: 10.1002/ajmg.1320490215] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A direct mutational analysis of the phenylalanine hydroxylase gene (PAH) in Gypsy families with phenylketonuria (PKU) has not yet been presented. However, they obviously represent a group at high risk for this inherited disease. We analyzed the PAH loci of 65 Gypsies originating from Eastern Slovakia by a combination of PCR amplification, direct sequencing and ASO hybridization. These studies uncovered 10 "classical PKU" patients to be homozygous for a R252W (CGG-TGG) transition, and 29 heterozygous carriers of this mutation. Fifteen control Caucasoid PKU patients from the Czech and Slovak Republics were selected. In this group we detected R252W mutation in two subjects (6.67% of all mutant alleles). Both were compound heterozygous for two different mutations. Previous haplotype studies of Welsh Gypsies with PKU were uninformative in the determination of heterozygosity. ASO hybridization served us effectively for the consequent analyses in Gypsy PKU-related families and to identify the carriers among the unrelated subjects.
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Affiliation(s)
- J Kalanin
- Third Department of Medicine, Institute for Clinical and Experimental Medicine, Praha, Czech Republic
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31
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Svensson E, Iselius L, Hagenfeldt L. Severity of mutation in the phenylalanine hydroxylase gene influences phenylalanine metabolism in phenylketonuria and hyperphenylalaninaemia heterozygotes. J Inherit Metab Dis 1994; 17:215-22. [PMID: 7967476 DOI: 10.1007/bf00711621] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We examined whether the degree of residual activity from the mutant phenylalanine hydroxylase (PAH) allele affected phenylalanine metabolism in heterozygotes for phenylketonuria (PKU) or non-PKU hyperphenylalaninaemia (HPA). Discriminant analysis was carried out to find the function of fasting plasma concentrations of phenylalanine (PHE) and tyrosine (TYR) that best separated carriers from non-carriers. This function (0.103TYR -0.214-PHECORR -4.499) was subsequently used as the dependent variable, with the in vitro activity of the expressed mutant PAH as the independent variable, in a regression analysis performed on heterozygotes for mutations that had been studied in a eukaryotic cell expression system. This analysis showed a significant correlation (r = 0.40, n = 140, p < 0.001), although there was a wide spread of values within each of the two major groups of carriers and a considerable overlap between the groups. We conclude that the severity of the mutation, as determined by in vitro expression analysis, in the mutant PAH gene is reflected in the biochemical phenotype of heterozygotes. This result emphasizes the relevance of the cell expression system used for establishing the relative severities of most mutations at the PAH locus. Differences in the activities from the carried mutant PAH allele on phenylalanine metabolism in heterozygotes are, however, small compared to the activity from the normal PAH allele and are easily obscured by other factors leading to inter- or intra-individual variation in phenylalanine metabolism. Fasting plasma concentrations of phenylalanine and tyrosine thus can not be used to predict the severity of the carried PAH mutation in individual PKU or HPA heterozygotes.
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Affiliation(s)
- E Svensson
- Department of Clinical Chemistry, Huddinge University Hospital, Sweden
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32
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Barić I, Mardesić D, Sarnavøka V, Lichter-Konecki U, Konecki DS, Trefz FK. Geographical distribution of the P281L mutation at the phenylalanine hydroxylase locus: possible origin in southeastern Europe. J Inherit Metab Dis 1994; 17:376-7. [PMID: 7807961 DOI: 10.1007/bf00711838] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- I Barić
- Department of Pediatrics, University Hospital Rebro, Zagreb, Croatia
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33
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Ramus SJ, Forrest SM, Pitt DB, Saleeba JA, Cotton RG. Comparison of genotype and intellectual phenotype in untreated PKU patients. J Med Genet 1993; 30:401-5. [PMID: 8320703 PMCID: PMC1016377 DOI: 10.1136/jmg.30.5.401] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We have screened 55 untreated phenylketonuria patients from 42 families for common mutations of the phenylalanine hydroxylase gene and determined both causative alleles in 12 families. The correlation between genotype and intellectual phenotype of patients in these families was examined. Our results were compared to a study which predicted phenylalanine hydroxylase activity based on genotype and examined its correlation with the biochemical phenotype of treated patients. Some of the intellectual phenotypes of patients in our study correlated well with the predicted activities. However, we found one family with a genotype expected to have no activity of phenylalanine hydroxylase where the patients were not severely retarded. Major differences in intellectual phenotype were found in patients with the same genotype both between unrelated subjects and within families, suggesting that there is not a simple correlation between genotype and intellectual phenotype.
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Affiliation(s)
- S J Ramus
- Olive Miller Protein Laboratory, Murdoch Institute, Royal Children's Hospital, Parkville, Victoria, Australia
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34
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Kleiman S, Vanagaite L, Bernstein J, Schwartz G, Brand N, Elitzur A, Woo SL, Shiloh Y. Phenylketonuria: variable phenotypic outcomes of the R261Q mutation and maternal PKU in the offspring of a healthy homozygote. J Med Genet 1993; 30:284-8. [PMID: 8487271 PMCID: PMC1016333 DOI: 10.1136/jmg.30.4.284] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Phenylketonuria (PKU) and benign hyperphenylalaninaemia (HPA) result from a variety of mutations in the gene for the hepatic enzyme phenylalanine hydroxylase. PKU has been found in the Israeli population in two variants, classical and atypical. The two are clinically indistinguishable and require treatment with low phenylalanine diet to prevent mental retardation, but show differences in serum phenylalanine levels and in tolerance to this amino acid. Maternal PKU is a syndrome of congenital anomalies and mental retardation that appears in offspring of PKU mothers as a result of fetal exposure to the high phenylalanine level in the maternal blood. We studied a family in which two children with severe, classical PKU and their unaffected brother showed mild signs of maternal PKU. Their mother had no clinical signs of PKU, but the phenylalanine concentration in her serum reached a level that usually characterises PKU patients. This woman represents a rare phenotype, benign atypical PKU. Such 'hidden' PKU in women may lead to maternal PKU in the offspring, similar to overt PKU. Special attention should therefore be paid to women having children with any of the clinical hallmarks of maternal PKU, and to children born to women known to have benign HPA. The mother was also found to be homozygous for a missense mutation at the phenylalanine hydroxylase locus, R261Q, which does not abolish enzymatic activity completely. In two other families, homozygosity for this mutation resulted in atypical PKU in four children. This observation suggests that mutations that do not completely destroy phenylalanine hydroxylase activity may exhibit variable phenotypic expression which is unpredictable. Compound heterozygosity for R261Q and other mutations led in other patients either to classical PKU or to mild benign HPA.
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Affiliation(s)
- S Kleiman
- Department of Human Genetics, Sackler School of Medicine, Tel Aviv University, Ramat Aviv, Israel
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35
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Jaruzelska J, Matuszak R, Lyonnet S, Rey F, Rey J, Filipowicz J, Borski K, Munnich A. Genetic background of clinical homogeneity of phenylketonuria in Poland. J Med Genet 1993; 30:232-4. [PMID: 8097262 PMCID: PMC1016306 DOI: 10.1136/jmg.30.3.232] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In order to elucidate the clinical homogeneity and severity of the hyperphenylalaninaemias in Poland, a total of 71 children with typical phenylketonuria (PKU) originating from western and northern Poland were screened for 13 mutations in the phenylalanine hydroxylase (PAH) gene. Eighty percent of all PKU alleles tested were found to carry an identified mutation. One mutation, namely the R408W mutation, accounted for more than 63% of mutant PAH alleles in Poland, the other 27% being accounted for by six mutations: IVS12nt1 (5%), IVSnt546 (5%), Y414C (4%), R252W (1.5%), R261Q (< 1%), and G272ter (< 1%). The predominance of the R408W mutation resulted in a high rate of homozygotes (35.2%) and compound heterozygotes for this mutation in children from western and northern Poland. The frequency and deleterious nature of this mutation probably accounts for the clinical homogeneity and severity of the hyperphenylalaninaemias in Poland. In addition, the high rate of the R408W mutation and its association with mutant haplotype 2 at the PAH locus in Poland give additional support to the Balto-Slavic origin of this mutant gene.
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Affiliation(s)
- J Jaruzelska
- Institute of Human Genetics, Polish Academy of Sciences, Poznań
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36
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Dianzani I, Camaschella C, Saglio G, Ferrero GB, Ramus S, Ponzone A, Cotton RG. Molecular analysis of contiguous exons of the phenylalanine hydroxylase gene: identification of a new PKU mutation. J Med Genet 1993; 30:228-31. [PMID: 8097261 PMCID: PMC1016305 DOI: 10.1136/jmg.30.3.228] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A modified application of the chemical cleavage of mismatch (CCM) method has been used to screen three contiguous exons (exons 9, 10, and 11) of the phenylalanine hydroxylase gene in 17 Italian PKU patients. A new nonsense heterozygous C-->G transversion within exon 11 (S359X) was identified in a single patient. Only one of the four mutations previously reported in this DNA region in Caucasians was found. This lesion, IVS X-546, was detected in five of the 34 PKU alleles examined. Our results underline the versatility of the CCM method for scanning a gene for multiple mutations.
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Affiliation(s)
- I Dianzani
- Istituto di Clinica Pediatrica, Università degli Studi di Torino, Italy
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37
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Svensson E, von Döbeln U, Eisensmith RC, Hagenfeldt L, Woo SL. Relation between genotype and phenotype in Swedish phenylketonuria and hyperphenylalaninemia patients. Eur J Pediatr 1993; 152:132-9. [PMID: 8444221 DOI: 10.1007/bf02072490] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Phenylketonuria (PKU) and hyperphenylalaninemia (HPA) are caused mostly by an inherited (autosomal recessive) deficiency in hepatic phenylalanine hydroxylase (PAH) activity. More than 50 PAH mutations have ben reported. The goal of the present study was to examine the molecular basis for the clinical heterogeneity of Swedish PKU and HPA patients. Mutations were identified through allele-specific oligonucleotide hybridization or DNA sequencing on 128 of the 176 mutant alleles (73%). Three mutations (R408W, Y414C and IVS12) together accounted for 56% of all mutant alleles and ten relatively infrequent mutations were found on another 17% of all mutant alleles. Patients from 50 of the 88 families (57%) had identified mutations in both PAH genes and allowed use to compare the clinical effects of different combinations of PAH mutations. The in vitro activity of all of these mutations, including the newly identified G272X and delta L364, have been tested in a eukaryotic expression system. There was a strong relationship between the average in vitro PAH activity of the two mutant enzymes and both the phenylalanine tolerance and the neonatal pretreatment serum phenylalanine concentration. This confirms previous observations in Danish and German PKU patients that disease phenotype is a consequence of the nature of the mutations at the PAH locus and not significantly influenced by other loci. The sample population in the previous study did not, however, include mild HPA patients, and the observed correlation is thus restricted to severe and moderate mutant alleles. Since a comparatively high proportion of the Swedish patients were mildly affected, we have provided additional evidence that this correlation is valid throughout a continuous spectrum of clinical varieties.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- E Svensson
- Howard Hughes Medical Institute, Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030
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38
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Knappskog M, Eiken HG, Martinez A, Olafsdotti S, Haavik J, Flatmark T, Apold J. Expression of wild type and mutant forms of human phenylalanine hydroxylase in E. coli. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1993; 338:59-62. [PMID: 8304187 DOI: 10.1007/978-1-4615-2960-6_11] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- M Knappskog
- Department of Medical Genetics, Haukeland Hospital, Bergen, Norway
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39
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Zygulska M, Eigel A, Pietrzyk JJ, Miny P, Horst J. A novel mutation in exon 8 of the phenylalanine hydroxylase gene in the Polish population. Hum Mutat 1993; 2:74-6. [PMID: 8097423 DOI: 10.1002/humu.1380020114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- M Zygulska
- Institut für Humangenetik, Universität, Münster, Germany
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Barić I, Mardesić D, Gjurić G, Sarnavka V, Göbel-Schreiner B, Lichter-Konecki U, Konecki DS, Trefz FK. Haplotype distribution and mutations at the PAH locus in Croatia. Hum Genet 1992; 90:155-7. [PMID: 1358784 DOI: 10.1007/bf00210763] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Restriction fragment length polymorphism (RFLP) haplotypes and mutations at the phenylalanine hydroxylase (PAH) locus have been studied in 25 unrelated families from Croatia. The results of RFLP analysis demonstrated that 80% of the mutant alleles were associated with three haplotypes (1, 2 and 4). Eight mutations were detected on the background of six mutant haplotypes, comprising 68% of phenylketonuria (PKU) alleles in Croatia. The mutation in codon 408 was most frequent, as was the haplotype 2 allele with which it was associated. These data are in accordance with formerly published population genetic analyses at the PAH locus, and with studies revealing the molecular basis of the phenotypic heterogeneity of PKU. The codon 281 mutation was more frequent in Croatia than previously observed in other populations.
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Affiliation(s)
- I Barić
- Department of Pediatrics, University Hospital Rebro, Zagreb, Croatia
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41
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Pérez B, Desviat LR, Die M, Ugarte M. Mutation analysis of phenylketonuria in Spain: prevalence of two Mediterranean mutations. Hum Genet 1992; 89:341-2. [PMID: 1601425 DOI: 10.1007/bf00220555] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We have screened seven Spanish phenylketonuric (PKU) families for the most prevalent Mediterranean and Caucasian mutations, and have subsequently found mutations P281L and IVS10. We have analyzed these two mutations in 23 of our patients. The frequencies found correspond to those of Mediterranean countries, such as Italy. This is the first report of a mutation analysis in the Spanish PKU population.
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Affiliation(s)
- B Pérez
- Centro de Biología Molecular, Universidad Autónoma de Madrid, Spain
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42
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Dworniczak B, Kalaydjieva L, Pankoke S, Aulehla-Scholz C, Allen G, Horst J. Analysis of exon 7 of the human phenylalanine hydroxylase gene: A mutation hot spot? Hum Mutat 1992; 1:138-46. [PMID: 1363786 DOI: 10.1002/humu.1380010209] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Complete sequence analysis of 194 human phenylalanine hydroxylase genes from PKU patients originating from West Germany and Bulgaria revealed 13 different mutations within exon 7 of the gene. Four of these mutations (T238P: ACT-->CCT; L242F:CTC-->TTC; R252G:CGG-->GGG; and 1043 delta 11: nt 1043-nt 1053 deleted) have so far not been described in the literature. Including these new mutations at least 21 different gene lesions and one sequence polymorphism exist for exon 7. Despite this large number unbiased calculation of the mutation frequency/exon size ratio does not provide conclusive evidence that exon 7 is a hot spot for disease causing mutations. Extensive screening during our experiments also failed to demonstrate the existence of excessive polymorphism in this part of the gene. It might therefore be speculated that the functional importance of the highly conserved exon 7 sequence accounts for the clustering of observed mutations which result in clinically manifest PKU. In addition we report our experience in regard to the resolution capacity of denaturing gradient gel electrophoresis (DGGE), a nonradioactive technique for the rapid screening of unknown mutations in exon 7.
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Affiliation(s)
- B Dworniczak
- Institute of Human Genetics, WWU, Münster, Germany
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43
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Eisensmith RC, Woo SL. Molecular basis of phenylketonuria and related hyperphenylalaninemias: mutations and polymorphisms in the human phenylalanine hydroxylase gene. Hum Mutat 1992; 1:13-23. [PMID: 1301187 DOI: 10.1002/humu.1380010104] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Mutations in the human phenylalanine hydroxylase gene producing phenylketonuria or hyperphenylalaninemia have now been identified in many patients from various ethnic groups. These mutations all exhibit a high degree of association with specific restriction fragment-length polymorphism haplotypes at the PAH locus. About 50 of these mutations are single-base substitutions, including six nonsense mutations and eight splicing mutations, with the remainder being missense mutations. One splicing mutation results in a 3 amino acid in-frame insertion. Two or 3 large deletions, 2 single codon deletions, and 2 single base deletions have been found. Twelve of the missense mutations apparently result from the methylation and subsequent deamination of highly mutagenic CpG dinucleotides. Recurrent mutation has been observed at several of these sites, producing associations with different haplotypes in different populations. About half of all missense mutations have been examined by in vitro expression analysis, and a significant correlation has been observed between residual PAH activity and disease phenotype. Since continuing advances in molecular methodologies have dramatically accelerated the rate in which new mutations are being identified and characterized, this register of mutations will be updated periodically.
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Affiliation(s)
- R C Eisensmith
- Howard Hughes Medical Institute, Baylor College of Medicine, Houston, Texas 77030
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44
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Okano Y, Hase Y, Lee DH, Furuyama J, Shintaku H, Oura T, Isshiki G. Frequency and distribution of phenylketonuric mutations in Orientals. Hum Mutat 1992; 1:216-20. [PMID: 1301927 DOI: 10.1002/humu.1380010307] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The frequency and distribution of eight mutations (R111X, IVS4nt-1, Y204C, R243Q, IVS7nt-2, W326X, Y356X, and R413P) in the phenylalanine hydroxylase gene of Orientals in Japan and Korea were examined by allele-specific oligonucleotide hybridization. The mutant alleles comprised 54 and 55% of the phenylketonuria (PKU) chromosomes examined in 36 patients in Japan and 10 patients in Korea, respectively. The spectrum of PKU mutations in Japan was similar to that in China, particularly in northern China, but different from that in Korea. The IVS4nt-1 mutation had a high frequency in Korea and southern China, due to the result of the founder effect and genetic drift. The R413P mutation, which may have originated in the regions surrounding the Baikal, expanded to northern China and Japan. We did not find Caucasian mutations in the Japanese or Korean PKU chromosomes. Thus, PKU mutations occurred after racial divergence between Caucasians and Mongoloids, and there were different founding populations for PKU in the two populations.
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Affiliation(s)
- Y Okano
- Department of Pediatrics, Osaka City University Medical School, Japan
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Svensson E, Eisensmith RC, Dworniczak B, von Döbeln U, Hagenfeldt L, Horst J, Woo SL. Two missense mutations causing mild hyperphenylalaninemia associated with DNA haplotype 12. Hum Mutat 1992; 1:129-37. [PMID: 1301200 DOI: 10.1002/humu.1380010208] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The genetic defects responsible for most phenylketonuria (PKU) and hyperphenylalaninemia (HPA) cases are located in the phenylalanine hydroxylase (PAH) gene. Approximately 50-60 mutations have been reported in Caucasians and are reflected in a wide range of clinical severities. Most mutations are linked to specific haplotypes, as defined by eight polymorphic restriction sites in the PAH gene. We hypothesized that there is at least one mild mutation linked to haplotype 12 in the Swedish PKU/HPA population, since 7 of 8 patients carrying haplotype 12 had mild HPA. Sequence analysis revealed a C-to-G transversion at the second base of codon 322, resulting in a substitution of glycine for alanine, in four mutant haplotype 12 genes, and a G-to-A transition at the second base of codon 408, resulting in a substitution of glutamine for arginine, in another three mutant haplotype 12 genes. These mutations segregated with mutant haplotype 12 alleles in nuclear families but were not present on normal or other mutant alleles. Both mutations were tested in a eukaryotic expression system in which enzyme activities of different mutant PAH enzymes reflect the relative severities of the mutations, although these in vitro activities cannot be translated directly into in vivo hepatic activities. The A322G mutant PAH had about 75% and the R408Q mutant PAH about 55% of the wild-type PAH enzyme activity. These in vitro activities are the highest reported for mutant PAH enzymes produced in the same expression system.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- E Svensson
- Howard Hughes Medical Institute, Department of Cell Biology, Houston, Texas
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Wang T, Okano Y, Eisensmith RC, Lo WH, Huang SZ, Zeng YT, Yuan LF, Liu SR, Woo SL. Missense mutations prevalent in Orientals with phenylketonuria: molecular characterization and clinical implications. Genomics 1991; 10:449-56. [PMID: 2071149 DOI: 10.1016/0888-7543(91)90331-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Two missense mutations in the phenylalanine hydroxylase (PAH) genes of Orientals with phenylketonuria (PKU) have been identified. A G-to-A transition in exon 7 of the gene results in the substitution of Gln243 for Arg243 (R243Q) and accounts for 18% of all PKU chromosomes among Chinese. An A-to-G transition in exon 6 of the gene results in the substitution of Cys204 for Tyr204 (Y204C) and identifies about 13 and 5% of all PKU chromosomes in the Chinese and Japanese populations, respectively. The R243Q construct produced less than 10% of normal PAH activity in in vitro expression analysis in a eukaryotic cell system, and patients homozygous for this substitution exhibit a severe clinical phenotype. These results are consistent with previous findings in this expression system. The Y204C construct, however, produced near normal levels of PAH enzyme activity and immunoreactivity in this in vitro expression system. Because this substitution is present only on PKU chromosomes, it is a valuable marker for identifying the corresponding mutant allele for carrier screening of PKU. With the characterization of these two substitutions, about 60% of PKU alleles in China can now be identified. The continuing search for additional PKU mutations will permit effective carrier screening and prenatal gene diagnosis of PKU in East Asia.
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Affiliation(s)
- T Wang
- Howard Hughes Medical Institute, Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030
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Okano Y, Eisensmith RC, Güttler F, Lichter-Konecki U, Konecki DS, Trefz FK, Dasovich M, Wang T, Henriksen K, Lou H. Molecular basis of phenotypic heterogeneity in phenylketonuria. N Engl J Med 1991; 324:1232-8. [PMID: 2014036 DOI: 10.1056/nejm199105023241802] [Citation(s) in RCA: 195] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
BACKGROUND Phenylketonuria is a metabolic disorder that results from a deficiency of the hepatic enzyme phenylalanine hydroxylase. Its clinical phenotype varies widely, and to date more than 10 mutations in the phenylalanine hydroxylase gene have been identified in persons with the disorder. We attempted to relate the clinical phenotype of patients to their genotype. METHODS We studied 258 patients with phenylketonuria from Denmark and Germany for the presence of eight mutations previously found in patients from these countries. The in vitro activity of the enzymes associated with these mutations was determined by expression analysis in heterologous mammalian cells. The level of activity was then used to predict the in vivo level of phenylalanine hydroxylase activity in patients with various combinations of mutant phenylalanine hydroxylase alleles. RESULTS The eight mutations involved 64 percent of all mutant phenylalanine hydroxylase alleles in the patients. Expression analysis showed that these mutant enzymes produced from 0 to 50 percent of normal enzyme activity. The predicted level of phenylalanine hydroxylase activity correlated strongly with the pretreatment serum level of phenylalanine (r = 0.91, P less than 0.001 in the Danish patients and r = 0.74, P less than 0.001 in the German patients), phenylalanine tolerance in the Danish patients (r = 0.84, P less than 0.001), and the serum phenylalanine level measured after standardized oral protein loading in the German patients (r = 0.84, P less than 0.001). CONCLUSIONS Our results strongly support the hypothesis that there is a molecular basis for phenotypic heterogeneity in phenylketonuria. The establishment of genotype will therefore aid in the prediction of biochemical and clinical phenotypes in patients with this disease.
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Affiliation(s)
- Y Okano
- Howard Hughes Medical Institute, Department of Cell Biology, Baylor College of Medicine, Houston, TX 77030
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