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Belosevic A, Minder AE, Gueuning M, van Breemen F, Thun GA, Mattle-Greminger MP, Meyer S, Baumer A, Minder EI, Schneider-Yin X, Barman-Aksözen J. First Report of a Low-Frequency Mosaic Mutation in the Hydroxymethylbilane Synthase Gene Causing Acute Intermittent Porphyria. Life (Basel) 2023; 13:1889. [PMID: 37763293 PMCID: PMC10533070 DOI: 10.3390/life13091889] [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: 08/14/2023] [Revised: 09/04/2023] [Accepted: 09/05/2023] [Indexed: 09/29/2023] Open
Abstract
Acute porphyrias are a group of monogenetic inborn errors of heme biosynthesis, characterized by acute and potentially life-threatening neurovisceral attacks upon exposure to certain triggering factors. Biochemical analyses can determine the type of acute porphyria, and subsequent genetic analysis allows for the identification of pathogenic variants in the specific gene, which provides information for family counselling. In 2017, a male Swiss patient was diagnosed with an acute porphyria while suffering from an acute attack. The pattern of porphyrin metabolite excretion in urine, faeces, and plasma was typical for an acute intermittent porphyria (AIP), which is caused by inherited autosomal dominant mutations in the gene for hydroxymethylbilane synthase (HMBS), the third enzyme in the heme biosynthetic pathway. However, the measurement of HMBS enzymatic activity in the erythrocytes was within the normal range and Sanger sequencing of the HMBS gene failed to detect any pathogenic variants. To explore the molecular basis of the apparent AIP in this patient, we performed third-generation long-read single-molecule sequencing (nanopore sequencing) on a PCR product spanning the entire HMBS gene, including the intronic sequences. We identified a known pathogenic variant, c.77G>A, p.(Arg26His), in exon 3 at an allelic frequency of ~22% in the patient's blood. The absence of the pathogenic variant in the DNA of the parents and the results of additional confirmatory studies supported the presence of a de novo mosaic mutation. To our knowledge, such a mutation has not been previously described in any acute porphyria. Therefore, de novo mosaic mutations should be considered as potential causes of acute porphyrias when no pathogenic genetic variant can be identified through routine molecular diagnostics.
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Affiliation(s)
- Adrian Belosevic
- Institute of Laboratory Medicine, Stadtspital Zürich, Triemli, 8063 Zurich, Switzerland
| | - Anna-Elisabeth Minder
- Division of Endocrinology, Diabetology, Porphyria and Clinical Nutrition, Stadtspital Zürich, Triemli, 8063 Zurich, Switzerland
- Swiss Reference Centre for Porphyrias, Stadtspital Zürich, Triemli, 8063 Zurich, Switzerland
| | - Morgan Gueuning
- Department of Research and Development, Blood Transfusion Service Zurich, Swiss Red Cross, 8952 Schlieren, Switzerland
| | - Franziska van Breemen
- Institute of Laboratory Medicine, Stadtspital Zürich, Triemli, 8063 Zurich, Switzerland
- Swiss Reference Centre for Porphyrias, Stadtspital Zürich, Triemli, 8063 Zurich, Switzerland
| | - Gian Andri Thun
- Department of Research and Development, Blood Transfusion Service Zurich, Swiss Red Cross, 8952 Schlieren, Switzerland
| | - Maja P. Mattle-Greminger
- Department of Research and Development, Blood Transfusion Service Zurich, Swiss Red Cross, 8952 Schlieren, Switzerland
| | - Stefan Meyer
- Department of Molecular Diagnostics and Cytometry, Blood Transfusion Service Zurich, Swiss Red Cross, 8952 Schlieren, Switzerland
| | - Alessandra Baumer
- Institute of Medical Genetics, University of Zürich, 8952 Schlieren, Switzerland
| | - Elisabeth I. Minder
- Division of Endocrinology, Diabetology, Porphyria and Clinical Nutrition, Stadtspital Zürich, Triemli, 8063 Zurich, Switzerland
- Swiss Reference Centre for Porphyrias, Stadtspital Zürich, Triemli, 8063 Zurich, Switzerland
| | - Xiaoye Schneider-Yin
- Institute of Laboratory Medicine, Stadtspital Zürich, Triemli, 8063 Zurich, Switzerland
- Swiss Reference Centre for Porphyrias, Stadtspital Zürich, Triemli, 8063 Zurich, Switzerland
| | - Jasmin Barman-Aksözen
- Institute of Laboratory Medicine, Stadtspital Zürich, Triemli, 8063 Zurich, Switzerland
- Swiss Reference Centre for Porphyrias, Stadtspital Zürich, Triemli, 8063 Zurich, Switzerland
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Longo M, Paolini E, Meroni M, Dongiovanni P. Cutting-Edge Therapies and Novel Strategies for Acute Intermittent Porphyria: Step-by-Step towards the Solution. Biomedicines 2022; 10:biomedicines10030648. [PMID: 35327450 PMCID: PMC8945550 DOI: 10.3390/biomedicines10030648] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/07/2022] [Accepted: 03/09/2022] [Indexed: 12/24/2022] Open
Abstract
Acute intermittent porphyria (AIP) is an autosomal dominant disease caused by the hepatic deficiency of porphobilinogen deaminase (PBGD) and the slowdown of heme biosynthesis. AIP symptomatology includes life-threatening, acute neurovisceral or neuropsychiatric attacks manifesting in response to precipitating factors. The latter promote the upregulation of 5-aminolevulinic acid synthase-1 (ALAS1), the first enzyme of heme biosynthesis, which promotes the overload of neurotoxic porphyrin precursors. Hemin or glucose infusions are the first-line therapies for the reduction of ALAS1 levels in patients with mild to severe AIP, while liver transplantation is the only curative treatment for refractory patients. Recently, the RNA-interference against ALAS1 was approved as a treatment for adult and adolescent patients with AIP. These emerging therapies aim to substitute dysfunctional PBGD with adeno-associated vectors for genome editing, human PBGD mRNA encapsulated in lipid nanoparticles, or PBGD protein linked to apolipoprotein A1. Finally, the impairment of glucose metabolism linked to insulin resistance, and mitochondrial aberrations during AIP pathophysiology provided new therapeutic targets. Therefore, the use of liver-targeted insulin and insulin-mimetics such as α-lipoic acid may be useful for overcoming metabolic dysfunction in these subjects. Herein, the present review aims to provide an overview of AIP pathophysiology and management, focusing on conventional and recent therapeutical approaches.
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Affiliation(s)
- Miriam Longo
- General Medicine and Metabolic Diseases, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Pad. Granelli, Via F Sforza 35, 20122 Milan, Italy; (M.L.); (E.P.); (M.M.)
- Department of Clinical Sciences and Community Health, Università degli Studi di Milano, 20122 Milan, Italy
| | - Erika Paolini
- General Medicine and Metabolic Diseases, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Pad. Granelli, Via F Sforza 35, 20122 Milan, Italy; (M.L.); (E.P.); (M.M.)
- Department of Pharmacological and Biomolecular Sciences, Università degli Studi di Milano, 20133 Milan, Italy
| | - Marica Meroni
- General Medicine and Metabolic Diseases, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Pad. Granelli, Via F Sforza 35, 20122 Milan, Italy; (M.L.); (E.P.); (M.M.)
| | - Paola Dongiovanni
- General Medicine and Metabolic Diseases, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Pad. Granelli, Via F Sforza 35, 20122 Milan, Italy; (M.L.); (E.P.); (M.M.)
- Correspondence: ; Tel.: +39-02-5503-3467; Fax: +39-02-5503-4229
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Ma L, Tian Y, Peng C, Zhang Y, Zhang S. Recent advances in the epidemiology and genetics of acute intermittent porphyria. Intractable Rare Dis Res 2020; 9:196-204. [PMID: 33139978 PMCID: PMC7586877 DOI: 10.5582/irdr.2020.03082] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 08/07/2020] [Accepted: 08/11/2020] [Indexed: 02/07/2023] Open
Abstract
Acute intermittent porphyria (AIP) is a dominant inherited disorder with a low penetrance that is caused by mutations in the gene coding for hydroxymethylbilane synthase (HMBS). Information about the epidemiology and molecular genetic features of this rare disorder is crucial to clinical research, and particularly to the evaluation of new treatments. Variations in the prevalence and penetrance of AIP in various studies may due to the different inclusion criteria and methods of assessment. Here, the prevalence and penetrance of AIP are analyzed systematically, and the genetic traits of different populations and findings regarding the genotype-phenotype correlation are summarized. In addition, quite a few studies have indicated that AIP susceptibility was affected by other factors, such as modifying genes. Findings regarding possible modifying genes are documented here, helping to reveal the pathogenesis of and treatments for AIP. The status of research on AIP in China reveals the lack of epidemiological and genetic studies of the Chinese population, a situation that needs to be promptly remedied.
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Affiliation(s)
- Liyan Ma
- Department of Endocrinology, The second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
| | - Yu Tian
- Department of Endocrinology, The second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
| | - Chenxing Peng
- Department of Endocrinology, The second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
| | - Yiran Zhang
- School of First Clinical Medical College, Southern Medical University, Guangzhou, Guangdong, China
| | - Songyun Zhang
- Department of Endocrinology, The second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
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Yasuda M, Chen B, Desnick RJ. Recent advances on porphyria genetics: Inheritance, penetrance & molecular heterogeneity, including new modifying/causative genes. Mol Genet Metab 2019; 128:320-331. [PMID: 30594473 PMCID: PMC6542720 DOI: 10.1016/j.ymgme.2018.11.012] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 11/26/2018] [Accepted: 11/26/2018] [Indexed: 12/16/2022]
Abstract
The inborn errors of heme biosynthesis, the Porphyrias, include eight major disorders resulting from loss-of-function (LOF) or gain-of-function (GOF) mutations in eight of the nine heme biosynthetic genes. The major sites of heme biosynthesis are the liver and erythron, and the underlying pathophysiology of each of these disorders depends on the unique biochemistry, cell biology, and genetic mechanisms in these tissues. The porphyrias are classified into three major categories: 1) the acute hepatic porphyrias (AHPs), including Acute Intermittent Porphyria (AIP), Hereditary Coproporphyria (HCP), Variegate Porphyria (VP), and 5-Aminolevlulinic Acid Dehydratase Deficient Porphyria (ADP); 2) a hepatic cutaneous porphyria, Porphyria Cutanea Tarda (PCT); and 3) the cutaneous erythropoietic porphyrias, Congenital Erythropoietic Porphyria (CEP), Erythropoietic Protoporphyria (EPP), and X-Linked Protoporphyria (XLP). Their modes of inheritance include autosomal dominant with markedly decreased penetrance (AIP, VP, and HCP), autosomal recessive (ADP, CEP, and EPP), or X-linked (XLP), as well as an acquired sporadic form (PCT). There are severe homozygous dominant forms of the three AHPs. For each porphyria, its phenotype, inheritance pattern, unique genetic principles, and molecular genetic heterogeneity are presented. To date, >1000 mutations in the heme biosynthetic genes causing their respective porphyrias have been reported, including low expression alleles and genotype/phenotype correlations that predict severity for certain porphyrias. The tissue-specific regulation of heme biosynthesis and the unique genetic mechanisms for each porphyria are highlighted.
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Affiliation(s)
- Makiko Yasuda
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States.
| | - Brenden Chen
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States.
| | - Robert J Desnick
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States.
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Granata F, Mendez M, Brancaleoni V, Castelbon FJ, Graziadei G, Ventura P, Di Pierro E. Molecular characterization, by digital PCR analysis of four HMBS gene mutations affecting the ubiquitous isoform of Porphobilinogen Deaminase (PBGD) in patients with Acute Intermittent Porphyria (AIP). Mol Genet Metab 2018; 125:295-301. [PMID: 30201327 DOI: 10.1016/j.ymgme.2018.09.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 09/03/2018] [Accepted: 09/03/2018] [Indexed: 12/12/2022]
Abstract
Genetic variants in promoters and alternative-splicing lesions require to be experimentally tested in order to validate them as causatives of a disease. The digital PCR (dPCR) approach, which is an alternative to the classical qPCR, is an innovative and a more sensitive method for the detection and quantification of nucleic acids. In the present study, we identified four HMBS gene mutations affecting the ubiquitous isoform of porphobilinogen deaminase (PBGD) and established a dPCR protocol which would be able to detect the different transcripts of this gene. With the application of this method, we were able to characterize the functional roles of these four genetic variants, demonstrating that all these mutations were causatives of the non-erythroid variant of the acute intermittent porphyria (AIP) disease.
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Affiliation(s)
- Francesca Granata
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, U.O.C. Medicina Generale, Milano, Italy
| | - Manuel Mendez
- Instituto de Investigación, Hospital 12 de Octubre, Madrid, Spain
| | - Valentina Brancaleoni
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, U.O.C. Medicina Generale, Milano, Italy
| | | | - Giovanna Graziadei
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, U.O.C. Medicina Generale, Milano, Italy
| | - Paolo Ventura
- Division of Internal Medicine 2 - Centre for Porphyrias, Dept. of Medical and Surgical Sciences for Children and Adults, University of Modena and Reggio Emilia, Policlinico Hospital, Modena, Italy
| | - Elena Di Pierro
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, U.O.C. Medicina Generale, Milano, Italy.
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Fortgens P, Pienaar E, Corrigall A, Sonderup M, Spearman CW, Meissner P. Molecular characterisation of acute intermittent porphyria in a cohort of South African patients and kinetic analysis of two expressed mutants. J Clin Pathol 2016; 70:515-520. [PMID: 27849156 DOI: 10.1136/jclinpath-2016-203907] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 10/20/2016] [Accepted: 10/25/2016] [Indexed: 11/04/2022]
Abstract
AIMS Acute intermittent porphyria (AIP) is a disorder of the haem biosynthetic pathway caused by mutations in the hydroxymethylbilane synthase (HMBS) gene. Knowledge of the spectrum of mutations present in South Africa is limited. This study presents the molecular profile of 20 South African patients with AIP, and the kinetic analysis of one novel expressed mutated HMBS enzyme and a previously identified mutation at the same position. METHODS Genomic DNA was isolated from affected probands and selected family members, the HMBS gene amplified and mutations characterised by direct sequencing and restriction enzyme analysis. One of the novel mutations (p.Lys98Glu), a previously characterised mutation at the same position (p.Lys98Arg), and the wild-type enzyme were expressed, purified and subjected to partial kinetic characterisation. RESULTS Four new mutations, p.Lys98Glu, p.Asp230Aspfs*20, c.161-1G>A and c.422+3_6delAAGT, are described. Seven previously described mutations were found, while four patients revealed no mutations. Mutation analysis of five offspring of one of the probands carrying the p.Trp283X mutation revealed two asymptomatic carriers. Kinetic analysis showed that the p.Lys98Glu mutation results in loss of substrate affinity, whereas the previously described p.Lys98Arg mutation causes the loss of binding between the enzyme and its dipyrromethane cofactor, rendering the enzyme inactive. CONCLUSIONS This study comprises the most comprehensive characterisation of HMBS gene mutations in patients with AIP in South Africa. The biochemical characterisation of expressed HMBS mutants reveals insight into the mechanism of catalytic activity loss, which may inspire investigation into individualised therapy based on the molecular lesion identified.
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Affiliation(s)
- Philip Fortgens
- Division of Chemical Pathology, Department of Pathology, Groote Schuur Hospital, University of Cape Town, Observatory, South Africa
| | - Elaine Pienaar
- Division of Medical Biochemistry, Department of Integrative Biomedical Sciences, Lennox Eales Porphyria Laboratory, University of Cape Town, Observatory, South Africa
| | - Anne Corrigall
- Lennox Eales Porphyria Laboratory, University of Cape Town, Observatory, South Africa
| | - Mark Sonderup
- Division of Hepatology, Department of Medicine, Groote Schuur Hospital, University of Cape Town, Observatory, South Africa
| | - C Wendy Spearman
- Division of Hepatology, Department of Medicine, Groote Schuur Hospital, University of Cape Town, Observatory, South Africa
| | - Peter Meissner
- Department of Integrative Biomedical Sciences, Lennox Eales Porphyria Laboratory, Structural Biology Research Unit, University of Cape Town, Observatory, South Africa
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The assessment of noncoding variant of PPOX gene in variegate porphyria reveals post-transcriptional role of the 5' untranslated exon 1. Blood Cells Mol Dis 2016; 61:48-53. [PMID: 27667166 DOI: 10.1016/j.bcmd.2016.08.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 08/05/2016] [Accepted: 08/06/2016] [Indexed: 11/23/2022]
Abstract
The PPOX gene encodes for the protoporphyrinogen oxidase, which is involved in heme production. The partial deficiency of protoporphyrinogen oxidase causes variegate porphyria. The tissue-specific regulation of other heme biosynthetic enzymes is extensively studied, but the information concerning transcriptional and post-transcriptional regulation of PPOX gene expression is scarcely available. In this study, we characterized functions of three variants identified in the regulatory regions of the PPOX gene, which show a novel role for the 5' untranslated exon 1. Using luciferase assays and RNA analysis, we demonstrated that only c.1-883G>C promoter variant causes a significant loss in the transcriptional activity of PPOX gene whereas c.1-413G>T 5' UTR variant inhibits translation of PPOX mRNA and c.1-176G>A splicing variant causes 4bp deletion in 5' UTR of PPOX mRNA variant 2. These observations indicate that the regulation of PPOX gene expression can also occur through a post-transcriptional modulation of the amount of gene product and that this modulation can be mediated by 5' untranslated exon 1. Moreover this study confirms that these regulatory regions represent an important molecular target for the pathogenesis of variegate porphyria.
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D’Avola D, Gonzalez Aseguinolaza G. Prospect and progress of gene therapy in acute intermittent porphyria. Expert Opin Orphan Drugs 2016. [DOI: 10.1080/21678707.2016.1191346] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Delia D’Avola
- Liver Unit, CIBERehd, and IDISNAt, Clinica Universidad Navarra, Pamplona, Spain
| | - Gloria Gonzalez Aseguinolaza
- Foundation for Applied Medical Research, Gene Therapy and Regulation of Gene Expression, CIMA, and IDISNA, Navarra, Spain
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Khulan B, Liu L, Rose CM, Boyle AK, Manning JR, Drake AJ. Glucocorticoids accelerate maturation of the heme pathway in fetal liver through effects on transcription and DNA methylation. Epigenetics 2016; 11:103-9. [PMID: 26889791 PMCID: PMC4846099 DOI: 10.1080/15592294.2016.1144006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Glucocorticoids are widely used in threatened preterm labor to promote maturation in many organ systems in preterm babies and have significant beneficial effects on morbidity and mortality. We performed transcriptional profiling in fetal liver in a rat model of prenatal glucocorticoid exposure and identified marked gene expression changes in heme biosynthesis, utilization, and degradation pathways in late gestation. These changes in gene expression associated with alterations in DNA methylation and with a reduction in hepatic heme concentration. There were no persistent differences in gene expression, DNA methylation, or heme concentrations at 4 weeks of age, suggesting that these are transient effects. Our findings are consistent with glucocorticoid-induced accelerated maturation of the haematopoietic system and support the hypothesis that glucocorticoids can drive changes in gene expression in association with alterations in DNA methylation.
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Affiliation(s)
- Batbayar Khulan
- a University/BHF Center for Cardiovascular Science, University of Edinburgh, Queen's Medical Research Institute , 47 Little France Crescent, Edinburgh , UK
| | - Lincoln Liu
- a University/BHF Center for Cardiovascular Science, University of Edinburgh, Queen's Medical Research Institute , 47 Little France Crescent, Edinburgh , UK
| | - Catherine M Rose
- a University/BHF Center for Cardiovascular Science, University of Edinburgh, Queen's Medical Research Institute , 47 Little France Crescent, Edinburgh , UK
| | - Ashley K Boyle
- a University/BHF Center for Cardiovascular Science, University of Edinburgh, Queen's Medical Research Institute , 47 Little France Crescent, Edinburgh , UK
| | - Jonathan R Manning
- a University/BHF Center for Cardiovascular Science, University of Edinburgh, Queen's Medical Research Institute , 47 Little France Crescent, Edinburgh , UK
| | - Amanda J Drake
- a University/BHF Center for Cardiovascular Science, University of Edinburgh, Queen's Medical Research Institute , 47 Little France Crescent, Edinburgh , UK
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Gonzaga ADG, de Amorim LMDF, Fonseca ABM, Nogueira TLS, Pereira OMD, Nagai MA, de Oliveira Barretto OC, Ribeiro GS. Hydroxymethylbilane synthase gene mutations and polymorphisms in Brazilian families with acute intermittent porphyria. Ann Hum Genet 2015; 79:162-72. [PMID: 25703257 DOI: 10.1111/ahg.12102] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 12/19/2014] [Indexed: 12/25/2022]
Abstract
Acute intermittent porphyria (AIP), an autosomal dominant disorder, is caused by a deficiency of hydroxymethylbilane synthase (HMBS). In the present study, we sought to establish a correlation between HMBS activity with the presence of mutations and polymorphisms. Enzyme activity was measured in red blood cells of four Brazilian unrelated AIP families (n = 124) and in blood donors (n = 80). The HMBS mutations in AIP family members were studied by PCR-SSCP followed by direct sequencing. Six intragenic SNPs (1345 G>A, 1500 T>C, 2377 C>A, 2478 A>G, 3581 A>G, and 7064 C>A) were determined by PCR-RFLP. Abnormal SSCP patterns in exons 7, 9, 12, and 15 were observed. DNA sequencing analysis revealed one nonsense mutation, R149X, two missense mutations, G111R and L338P, and one deletion, CT 730-731. All mutation carriers had lower enzyme activity. All polymorphisms, except 2377 C>A and 7064 C>A, showed no significant differences compared with previous reports. Mutation screening allowed the detection of the missense mutation, L338P, and the 730_731delCT deletion, two as yet unreported mutations in Brazilian AIP patients. Our findings also showed a high frequency of 2478 A>G and 3581 A>G polymorphism combinations suggesting that these polymorphisms contributed to enzymatic activity reduction in our study population.
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Affiliation(s)
- Ana Denise Gomes Gonzaga
- Departamento de Patologia, Faculdade de Medicina, Universidade Federal Fluminense, Niterói, RJ, Brazil
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