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Wang YC, Lan LC, Yang X, Xiao J, Liu HX, Shan QW. A case report of classic galactosemia with a GALT gene variant and a literature review. BMC Pediatr 2024; 24:352. [PMID: 38778342 PMCID: PMC11110268 DOI: 10.1186/s12887-024-04769-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Accepted: 04/16/2024] [Indexed: 05/25/2024] Open
Abstract
BACKGROUND Galactosemia is an autosomal recessive disorder resulting from an enzyme defect in the galactose metabolic pathway. The most severe manifestation of classic galactosemia is caused by galactose-1-phosphate uridylyltransferase (GALT) deficiency, and this condition can be fatal during infancy if left untreated. It also may result in long-term complications in affected individuals. CASE PRESENTATION This report describes a patient whose initial clinical symptoms were jaundice and liver dysfunction. The patient's liver and coagulation functions did not improve after multiple admissions and treatment with antibiotics, hepatoprotective and choleretic agents and blood transfusion. Genetic analysis revealed the presence of two variants in the GALT gene in the compound heterozygous state: c.377 + 2dup and c.368G > C (p.Arg123Pro). Currently, the variant locus (c.377 + 2dup) in the GALT gene has not been reported in the Human Gene Mutation Database (HGMD), while c.368G > C (p.Arg123Pro) has not been reported in the Genome Aggregation Database (GnomAD) nor the HGMD in East Asian population. We postulated that the two variants may contribute to the development of classical galactosemia. CONCLUSIONS Applications of whole-exome sequencing to detect the two variants can improve the detection and early diagnosis of classical galactosemia and, more specifically, may identify individuals who are compound heterozygous with variants in the GALT gene. Variants in the GALT gene have a potential therapeutic significance for classical galactosemia.
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Affiliation(s)
- Yong-Cai Wang
- Difficult and Critical Illness Center, Pediatric Clinical Medical Research Center of Guangxi, The First Affiliated Hospital of Guangxi Medical University, No. 6 Shuangyong Road, Nanning, 530021, Guangxi Zhuang Autonomous Region, China
- Dazhou Central Hosptial, No. 56 Nanyuemiao Street, Tongchuan District, Dazhou, 635000, Sichuan Province, China
| | - Lian-Cheng Lan
- Difficult and Critical Illness Center, Pediatric Clinical Medical Research Center of Guangxi, The First Affiliated Hospital of Guangxi Medical University, No. 6 Shuangyong Road, Nanning, 530021, Guangxi Zhuang Autonomous Region, China
| | - Xia Yang
- Difficult and Critical Illness Center, Pediatric Clinical Medical Research Center of Guangxi, The First Affiliated Hospital of Guangxi Medical University, No. 6 Shuangyong Road, Nanning, 530021, Guangxi Zhuang Autonomous Region, China
| | - Juan Xiao
- Difficult and Critical Illness Center, Pediatric Clinical Medical Research Center of Guangxi, The First Affiliated Hospital of Guangxi Medical University, No. 6 Shuangyong Road, Nanning, 530021, Guangxi Zhuang Autonomous Region, China
| | - Hai-Xin Liu
- Difficult and Critical Illness Center, Pediatric Clinical Medical Research Center of Guangxi, The First Affiliated Hospital of Guangxi Medical University, No. 6 Shuangyong Road, Nanning, 530021, Guangxi Zhuang Autonomous Region, China
| | - Qing-Wen Shan
- Difficult and Critical Illness Center, Pediatric Clinical Medical Research Center of Guangxi, The First Affiliated Hospital of Guangxi Medical University, No. 6 Shuangyong Road, Nanning, 530021, Guangxi Zhuang Autonomous Region, China.
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Almenabawy N, Bahl S, Ostlund AL, Ghai-Jain S, Sosova I, Chan A, Mercimek-Andrews S. Clinical and biochemical phenotypes, genotypes, and long-term outcomes of individuals with galactosemia type I from a single metabolic genetics center in Alberta. Mol Genet Metab Rep 2024; 38:101055. [PMID: 38469090 PMCID: PMC10926219 DOI: 10.1016/j.ymgmr.2024.101055] [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: 11/10/2023] [Revised: 01/12/2024] [Accepted: 01/15/2024] [Indexed: 03/13/2024] Open
Abstract
Background Galactosemia type I is an autosomal recessive disorder of galactose metabolism due to galactose-1-phosphate uridyltransferase deficiency, encoded by GALT. To investigate the phenotypes, genotypes and long-term outcomes of galactosemia, we performed a retrospective cohort study in our center. Methods All individuals with galactosemia type I were included. We divided individuals into two groups to compare the outcomes of those treated symptomatically (SymX) and asymptomatically (AsymX). We reviewed electronic patient charts for clinical features, biochemical investigations, molecular genetic investigations, treatments, and outcomes. Results There were 25 individuals including classic (n = 17), clinical variant (n = 4), and biochemical variant (Duarte) galactosemia (n = 4). Twelve individuals were diagnosed symptomatically (SymX), and 9 individuals were diagnosed asymptomatically (AsymX). We did not include individuals with biochemical variant (Duarte) galactosemia into any of these groups. At the time of the diagnosis, conjugated hyperbilirubinemia was present in 83.3% of SymX group, whereas only 22% of AsymX group. SymX group had hepatomegaly (25%), failure to thrive (33.3%), cataract (16.7%) and sepsis (25%), whereas none of the individuals in the AsymX group had these clinical features. Fourteen variants in GALT were identified including pathogenic/likely pathogenic (n = 12), and likely benign/benign (n = 2) variants. The vast majority of individuals with classic and clinical variant galactosemia were treated with a galactose-lactose-free diet for life (n = 20/21). Intellectual disability was present in 54.5% of the SymX group, and in 37.5% of the AsymX group as a long-term outcome. Tremors were present 50% of the SymX group, and in 22% of the AsymX group as a long-term outcome. Although, intellectual disability and tremors seem to be less common in the AsymX group, there was no statistically significant difference between both groups. Primary ovarian insufficiency was present 50% of the SymX group, whereas in 20% of the AsymX group in post-pubertal females. We report a novel hypomorphic GALT variant (p.Ala303Ser) in one individual with clinical variant galactosemia. We also report an individual with clinical variant galactosemia with normal urine galactitol levels on a normal diet. Conclusion It seems that newborn screening and early administration of a galactose-lactose-free diet decreases the long-term galactosemia-associated complications but does not prevent them completely. It may be that not all individuals with clinical variant galactosemia may need a galactose-lactose-free diet. It is timely to find new therapeutic strategies that can reduce the frequency of late-onset complications in galactosemia.
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Affiliation(s)
- Nihal Almenabawy
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Shalini Bahl
- Princess Margaret Cancer Centre, 101 College Street, Toronto, ON M5G 1L7, Canada
- Department of Medical Biophysics, University of Toronto, 101 College Street, Toronto, ON M5G 1L7, Canada
| | - Alyssa-Lyn Ostlund
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Shailly Ghai-Jain
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Iveta Sosova
- Alberta Newborn Screening and Biochemical Genetics Laboratory, University of Alberta Hospital, Alberta Precision Laboratories, Edmonton, AB, Canada
- Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, AB, Canada
| | - Alicia Chan
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Saadet Mercimek-Andrews
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
- Alberta Health Services, AB, Canada
- Women's and Children's Research Institute, University of Alberta, Canada
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Viggiano E, Marabotti A, Politano L, Burlina A. Galactose-1-phosphate uridyltransferase deficiency: A literature review of the putative mechanisms of short and long-term complications and allelic variants. Clin Genet 2017; 93:206-215. [PMID: 28374897 DOI: 10.1111/cge.13030] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 03/29/2017] [Accepted: 03/31/2017] [Indexed: 12/30/2022]
Abstract
Galactosemia type 1 is an autosomal recessive disorder of galactose metabolism, determined by a deficiency in the enzyme galactose-1-phosphate uridyltransferase (GALT). GALT deficiency is classified as severe or variant depending on biochemical phenotype, genotype and potential to develop acute and long-term complications. Neonatal symptoms usually resolve after galactose-restricted diet; however, some patients, despite the diet, can develop long-term complications, in particular when the GALT enzyme activity results absent or severely decreased. The mechanisms of acute and long-term complications are still discussed and several hypotheses are presented in the literature like enzymatic inhibition, osmotic stress, endoplasmic reticulum stress, oxidative stress, defects of glycosylation or epigenetic modification. This review summarizes the current knowledge of galactosemia, in particular the putative mechanisms of neonatal and long-term complications and the molecular genetics of GALT deficiency.
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Affiliation(s)
- E Viggiano
- Division of Metabolic Diseases, Department of Paediatrics, University Hospital of Padua, Padua, Italy.,Cardiomyology and Medical Genetics, Department of Experimental Medicine, Second University of Naples, Naples, Italy
| | - A Marabotti
- Department of Chemistry and Biology "A. Zambelli", University of Salerno, Salerno, Italy.,Interuniversity Center "ELFID", University of Salerno, Fisciano, Italy
| | - L Politano
- Cardiomyology and Medical Genetics, Department of Experimental Medicine, Second University of Naples, Naples, Italy
| | - A Burlina
- Division of Metabolic Diseases, Department of Paediatrics, University Hospital of Padua, Padua, Italy
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Coelho AI, Rubio-Gozalbo ME, Vicente JB, Rivera I. Sweet and sour: an update on classic galactosemia. J Inherit Metab Dis 2017; 40:325-342. [PMID: 28281081 PMCID: PMC5391384 DOI: 10.1007/s10545-017-0029-3] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 02/14/2017] [Accepted: 02/20/2017] [Indexed: 02/03/2023]
Abstract
Classic galactosemia is a rare inherited disorder of galactose metabolism caused by deficient activity of galactose-1-phosphate uridylyltransferase (GALT), the second enzyme of the Leloir pathway. It presents in the newborn period as a life-threatening disease, whose clinical picture can be resolved by a galactose-restricted diet. The dietary treatment proves, however, insufficient in preventing severe long-term complications, such as cognitive, social and reproductive impairments. Classic galactosemia represents a heavy burden on patients' and their families' lives. After its first description in 1908 and despite intense research in the past century, the exact pathogenic mechanisms underlying galactosemia are still not fully understood. Recently, new important insights on molecular and cellular aspects of galactosemia have been gained, and should open new avenues for the development of novel therapeutic strategies. Moreover, an international galactosemia network has been established, which shall act as a platform for expertise and research in galactosemia. Herein are reviewed some of the latest developments in clinical practice and research findings on classic galactosemia, an enigmatic disorder with many unanswered questions warranting dedicated research.
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Affiliation(s)
- Ana I Coelho
- Department of Pediatrics and Department of Clinical Genetics, Maastricht University Medical Centre, P. Debyelaan 25, PO Box 5800, 6202 AZ, Maastricht, The Netherlands.
| | - M Estela Rubio-Gozalbo
- Department of Pediatrics and Department of Clinical Genetics, Maastricht University Medical Centre, P. Debyelaan 25, PO Box 5800, 6202 AZ, Maastricht, The Netherlands
| | - João B Vicente
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Isabel Rivera
- Metabolism & Genetics Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal
- Department of Biochemistry and Human Biology, Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal
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5
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Viggiano E, Marabotti A, Burlina AP, Cazzorla C, D'Apice MR, Giordano L, Fasan I, Novelli G, Facchiano A, Burlina AB. Clinical and molecular spectra in galactosemic patients from neonatal screening in northeastern Italy: structural and functional characterization of new variations in the galactose-1-phosphate uridyltransferase (GALT) gene. Gene 2015; 559:112-8. [PMID: 25592817 DOI: 10.1016/j.gene.2015.01.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 12/29/2014] [Accepted: 01/08/2015] [Indexed: 10/24/2022]
Abstract
Classical galactosemia is an autosomal recessive inborn error of metabolism due to mutations of the GALT gene leading to toxic accumulation of galactose and derived metabolites. With the benefit of early diagnosis by neonatal screening and early therapy, the acute presentation of classical galactosemia can be prevented. However, despite early diagnosis and treatment, the long term outcome for these patients is still unpredictable because they may go on to develop cognitive disability, speech problems, neurological and/or movement disorders and, in females, ovarian dysfunction. The objectives of the current study were to report our experience with a group of galactosemic patients identified through the neonatal screening programs in northeastern Italy during the last 30years. No neonatal deaths due to galactosemia complications occurred after the introduction of the neonatal screening program. However, despite the early diagnosis and dietary treatment, the patients with classical galactosemia showed one or more long-term complications. A total of 18 different variations in the GALT gene were found in the patient cohort: 12 missense, 2 frameshift, 1 nonsense, 1 deletion, 1 silent variation, and 1 intronic. Six (p.R33P, p.G83V, p.P244S, p.L267R, p.L267V, p.E271D) were new variations. The most common variation was p.Q188R (12 alleles, 31.5%), followed by p.K285N (6 alleles, 15.7%) and p.N314D (6 alleles, 15.7%). The other variations comprised 1 or 2 alleles. In the patients carrying a new mutation, the biochemical analysis of GALT activity in erythrocytes showed an activity of <1%. In silico analysis (SIFT, PolyPhen-2 and the computational analysis on the static protein structure) showed potentially damaging effects of the six new variations on the GALT protein, thus expanding the genetic spectrum of GALT variations in Italy. The study emphasizes the difficulty in establishing a genotype-phenotype correlation in classical galactosemia and underlines the importance of molecular diagnostic testing prior to making any treatment.
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Affiliation(s)
- E Viggiano
- Division of Inborn Metabolic Diseases, Department of Paediatrics, University Hospital of Padova, Italy
| | - A Marabotti
- Department of Chemistry and Biology, University of Salerno, via Giovanni Paolo II 132, 84084 Fisciano, SA, Italy
| | - A P Burlina
- Neurological Unit, St. Bassiano Hospital, Bassano del Grappa, Consultant in Neurometabolic Hereditary Diseases at the University Hospital of Padova, Italy
| | - C Cazzorla
- Division of Inborn Metabolic Diseases, Department of Paediatrics, University Hospital of Padova, Italy
| | - M R D'Apice
- Department of Biomedicine and Prevention, School of Medicine, University of Rome "Tor Vergata" and Fondazione PTV "Policlinico Tor Vergata", Rome, Italy
| | - L Giordano
- Division of Inborn Metabolic Diseases, Department of Paediatrics, University Hospital of Padova, Italy
| | - I Fasan
- Division of Inborn Metabolic Diseases, Department of Paediatrics, University Hospital of Padova, Italy
| | - G Novelli
- Department of Biomedicine and Prevention, School of Medicine, University of Rome "Tor Vergata" and Fondazione PTV "Policlinico Tor Vergata", Rome, Italy
| | - A Facchiano
- National Research Council, Institute of Food Science, via Roma 64, 83100 Avellino, Italy
| | - A B Burlina
- Division of Inborn Metabolic Diseases, Department of Paediatrics, University Hospital of Padova, Italy.
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d'Acierno A, Facchiano A, Marabotti A. GALT protein database: querying structural and functional features of GALT enzyme. Hum Mutat 2014; 35:1060-7. [PMID: 24990533 DOI: 10.1002/humu.22613] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 06/24/2014] [Indexed: 01/19/2023]
Abstract
Knowledge of the impact of variations on protein structure can enhance the comprehension of the mechanisms of genetic diseases related to that protein. Here, we present a new version of GALT Protein Database, a Web-accessible data repository for the storage and interrogation of structural effects of variations of the enzyme galactose-1-phosphate uridylyltransferase (GALT), the impairment of which leads to classic Galactosemia, a rare genetic disease. This new version of this database now contains the models of 201 missense variants of GALT enzyme, including heterozygous variants, and it allows users not only to retrieve information about the missense variations affecting this protein, but also to investigate their impact on substrate binding, intersubunit interactions, stability, and other structural features. In addition, it allows the interactive visualization of the models of variants collected into the database. We have developed additional tools to improve the use of the database by nonspecialized users. This Web-accessible database (http://bioinformatica.isa.cnr.it/GALT/GALT2.0) represents a model of tools potentially suitable for application to other proteins that are involved in human pathologies and that are subjected to genetic variations.
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Coelho AI, Trabuco M, Ramos R, Silva MJ, Tavares de Almeida I, Leandro P, Rivera I, Vicente JB. Functional and structural impact of the most prevalent missense mutations in classic galactosemia. Mol Genet Genomic Med 2014; 2:484-96. [PMID: 25614870 PMCID: PMC4303218 DOI: 10.1002/mgg3.94] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Revised: 05/20/2014] [Accepted: 05/22/2014] [Indexed: 11/10/2022] Open
Abstract
Galactose-1-phosphate uridylyltransferase (GALT) is a key enzyme in galactose metabolism, particularly important in the neonatal period due to ingestion of galactose-containing milk. GALT deficiency results in the genetic disorder classic galactosemia, whose pathophysiology is still not fully elucidated. Whereas classic galactosemia has been hypothesized to result from GALT misfolding, a thorough functional-structural characterization of GALT most prevalent variants was still lacking, hampering the development of alternative therapeutic approaches. The aim of this study was to investigate the structural-functional effects of nine GALT mutations, four of which account for the vast majority of the mutations identified in galactosemic patients. Several methodologies were employed to evaluate the mutations' impact on GALT function, on the protein secondary and tertiary structures, and on the aggregation propensity. The major structural effect concerns disturbed propensity for aggregation, particularly striking for the p.Q188R variant, resulting from the most frequent (∼60%) allele at a worldwide scale. The absence of major effects at the secondary and tertiary structure levels suggests that the disturbed aggregation results from subtle perturbations causing a higher and/or longer exposure of hydrophobic residues in the variants as compared to WT GALT. The results herein described indicate a possible benefit from introducing proteostasis regulators and/or chemical/pharmacological chaperones to prevent the accumulation of protein aggregates, in new avenues of therapeutic research for classic galactosemia.
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Affiliation(s)
- Ana I Coelho
- Metabolism and Genetics Group, Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon 1649-003, Lisbon, Portugal
| | - Matilde Trabuco
- Metabolism and Genetics Group, Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon 1649-003, Lisbon, Portugal
| | - Ruben Ramos
- Metabolism and Genetics Group, Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon 1649-003, Lisbon, Portugal
| | - Maria João Silva
- Metabolism and Genetics Group, Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon 1649-003, Lisbon, Portugal ; Department of Biochemistry and Human Biology, Faculty of Pharmacy, University of Lisbon 1649-003, Lisbon, Portugal
| | - Isabel Tavares de Almeida
- Metabolism and Genetics Group, Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon 1649-003, Lisbon, Portugal ; Department of Biochemistry and Human Biology, Faculty of Pharmacy, University of Lisbon 1649-003, Lisbon, Portugal
| | - Paula Leandro
- Metabolism and Genetics Group, Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon 1649-003, Lisbon, Portugal ; Department of Biochemistry and Human Biology, Faculty of Pharmacy, University of Lisbon 1649-003, Lisbon, Portugal
| | - Isabel Rivera
- Metabolism and Genetics Group, Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon 1649-003, Lisbon, Portugal ; Department of Biochemistry and Human Biology, Faculty of Pharmacy, University of Lisbon 1649-003, Lisbon, Portugal
| | - João B Vicente
- Metabolism and Genetics Group, Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon 1649-003, Lisbon, Portugal ; Department of Biochemistry and Human Biology, Faculty of Pharmacy, University of Lisbon 1649-003, Lisbon, Portugal
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Pyhtila BM, Shaw KA, Neumann SE, Fridovich-Keil JL. Newborn screening for galactosemia in the United States: looking back, looking around, and looking ahead. JIMD Rep 2014; 15:79-93. [PMID: 24718839 DOI: 10.1007/8904_2014_302] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Revised: 02/05/2014] [Accepted: 02/14/2014] [Indexed: 12/17/2022] Open
Abstract
It has been 50 years since the first newborn screening (NBS) test for galactosemia was conducted in Oregon, and almost 10 years since the last US state added galactosemia to their NBS panel. During that time an estimated >2,500 babies with classic galactosemia have been identified by NBS. Most of these infants were spared the trauma of acute disease by early diagnosis and intervention, and many are alive today because of NBS. Newborn screening for galactosemia is a success story, but not yet a story with a completely happy ending. NBS, follow-up testing, and intervention for galactosemia continue to present challenges that highlight gaps in our knowledge. Here we compare galactosemia screening and follow-up data from 39 NBS programs gathered from the states directly or from public sources. On some matters the programs agreed: for example, those providing relevant data all identify classic galactosemia in close to 1/50,000 newborns and recommend immediate and lifelong dietary restriction of galactose for those infants. On other matters the programs disagree. For example, Duarte galactosemia (DG) detection rates vary dramatically among states, largely reflecting differences in screening approach. For infants diagnosed with DG, >80% of the programs surveyed recommend complete or partial dietary galactose restriction for the first year of life, or give mixed recommendations; <20% recommend no intervention. This disparity presents an ongoing dilemma for families and healthcare providers that could and should be resolved.
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Affiliation(s)
- Brook M Pyhtila
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, 30322, USA
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Phenotype-Genotype Discrepancy Due to a 5.5-kb Deletion in the GALT Gene. JIMD Rep 2013. [PMID: 23430845 DOI: 10.1007/8904_2011_30] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] Open
Abstract
Classical galactosemia is an autosomal recessive inborn error of metabolism caused by a deficiency of the galactose-1-phosphate uridyltransferase (GALT). More than 200 mutations have been described in the GALT gene. A 5.5-kb GALT deletion, first described in patients of Ashkenazi Jewish ancestry, may lead either to an erroneous genotype assignment of classical galactosemia or to discrepancies with parental genotypes and the expected biochemical phenotype. The presence of the 5.5-kb deletion was examined in 27 Mexican nonrelated families with at least one child with reduced GALT activity in erythrocytes and it was detected in the 5.5% (n=3) of the 54 alleles tested. The first molecular studies in three of our families showed that the genotypes of the parents were inconsistent with those of their children, which were considered initially as homozygous p.N314D-Duarte 2, but after analyzing for the presence of the 5.5-kb deletion, were reassigned as compound heterozygotes [5.5-kb deletion]+[p.N314D-Duarte 2]. Identification of the 5.5-kb deletion in Mexican patients suggests that this mutation might not be exclusive to a given ethnic group and should be tested in other populations, especially when there is a discrepancy between the genotypes of patients and parents or by incongruence between biochemical phenotype and GALT genotype. Establishing a genotype-phenotype correlation for the 5.5-kb GALT deletion and determining the appropriate management will require additional studies in patients with a G/G genotype bearing the 5.5-kb GALT deletion.
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Merritt MA, Kotsopoulos J, Cramer DW, Hankinson SE, Terry KL, Tworoger SS. Duarte galactose-1-phosphate uridyl transferase genotypes are not associated with ovarian cancer risk. Fertil Steril 2012; 98:687-91. [DOI: 10.1016/j.fertnstert.2012.05.045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 05/30/2012] [Accepted: 05/30/2012] [Indexed: 11/28/2022]
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Frequency distribution of Q188R, N314D, Duarte 1, and Duarte 2 GALT variant alleles in an Indian galactosemia population. Biochem Genet 2012; 50:871-80. [PMID: 22798028 DOI: 10.1007/s10528-012-9527-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2011] [Accepted: 06/20/2012] [Indexed: 10/28/2022]
Abstract
Classical galactosemia is a genetic disorder caused by mutations in the galactose-1-phosphate uridyltransferase (GALT) gene. The Q188R and N314D mutations are the most frequently cited GALT gene mutations. N314D is further associated with two variants, Duarte 1 and Duarte 2. Nevertheless, no reports are available on the clinical and molecular spectrum of galactosemia from the Indian population. The present study was designed to establish the frequency of these two most common mutations and their variants in Indian galactosemia patients so as to determine a single most common mutation/polymorphism for establishing the DNA-based diagnosis of galactosemia. Three alleles were found to be present at a frequency of 0.036 (Q188R), 0.40 (N314D), and 0.39 (D2); no D1 alleles were found. A significantly higher frequency of the Duarte 2 allele in our population suggests the presence of a milder form of galactosemia, which can be well managed by early diagnosis and dietary management.
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McCorvie TJ, Timson DJ. Structural and molecular biology of type I galactosemia: disease-associated mutations. IUBMB Life 2011; 63:949-54. [PMID: 21960482 DOI: 10.1002/iub.510] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Accepted: 05/06/2011] [Indexed: 11/06/2022]
Abstract
Type I galactosemia results from reduced galactose 1-phosphate uridylyltransferase (GALT) activity. Signs of disease include damage to the eyes, brain, liver, and ovaries. However, the exact nature and severity of the pathology depends on the mutation(s) in the patient's genes and his/her environment. Considerable enzymological and structural knowledge has been accumulated and this provides a basis to explain, at a biochemical level, impairment in the enzyme in the more than 230 disease-associated variants, which have been described. The most common variant, Q188R, occurs close to the active site and the dimer interface. The substitution probably disrupts both UDP-sugar binding and homodimer stability. Other alterations, for example K285N, occur close to the surface of the enzyme and most likely affect the folding and stability of the enzyme. There are a number of unanswered questions in the field, which require resolution. These include the possibility that the main enzymes of galactose metabolism form a supramolecular complex and the need for a high resolution crystal structure of human GALT.
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Affiliation(s)
- Thomas J McCorvie
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, Belfast, Northern Ireland, UK
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The role of human demographic history in determining the distribution and frequency of transferase-deficient galactosaemia mutations. Heredity (Edinb) 2009; 104:148-54. [DOI: 10.1038/hdy.2009.84] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Carney AE, Sanders RD, Garza KR, McGaha LA, Bean LJH, Coffee BW, Thomas JW, Cutler DJ, Kurtkaya NL, Fridovich-Keil JL. Origins, distribution and expression of the Duarte-2 (D2) allele of galactose-1-phosphate uridylyltransferase. Hum Mol Genet 2009; 18:1624-32. [PMID: 19224951 PMCID: PMC2667289 DOI: 10.1093/hmg/ddp080] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Duarte galactosemia is a mild to asymptomatic condition that results from partial impairment of galactose-1-phosphate uridylyltransferase (GALT). Patients with Duarte galactosemia demonstrate reduced GALT activity and carry one profoundly impaired GALT allele (G) along with a second, partially impaired GALT allele (Duarte-2, D2). Molecular studies reveal at least five sequence changes on D2 alleles: a p.N314D missense substitution, three intronic base changes and a 4 bp deletion in the 5′ proximal sequence. The four non-coding sequence changes are unique to D2. The p.N314D substitution, however, is not; it is found together with a silent polymorphism, p.L218(TTA), on functionally normal Duarte-1 alleles (D1, also called Los Angeles or LA alleles). The HapMap database reveals that p.N314D is a common human variant, and cross-species comparisons implicate D314 as the ancestral allele. The p.N314D substitution is also functionally neutral in mammalian cell and yeast expression studies. In contrast, the 4 bp 5′ deletion characteristic of D2 alleles appears to be functionally impaired in reporter gene transfection studies. Here we present allele-specific qRT–PCR evidence that D2 alleles express less mRNA in vivo than their wild-type counterparts; the difference is small but statistically significant. Furthermore, we characterize the prevalence of the 4 bp deletion in GG, NN and DG populations; the deletion appears exclusive to D2 alleles. Combined, these data strongly implicate the 4 bp 5′ deletion as a causal mutation in Duarte galactosemia and suggest that direct tests for this deletion, as proposed here, could enhance or supplant current tests, which define D2 alleles on the basis of the presence and absence of linked coding sequence polymorphisms.
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15
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Velázquez-Aragón J, Alcántara-Ortigoza MA, Vela-Amieva M, Monroy S, Martínez-Cruz V, Todd-Quiñones C, González-del Angel A. Low allelic heterogeneity in a sample of Mexican patients with classical galactosaemia. J Inherit Metab Dis 2008; 31 Suppl 2:S333-7. [PMID: 18956253 DOI: 10.1007/s10545-008-0905-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2008] [Revised: 09/03/2008] [Accepted: 09/08/2008] [Indexed: 11/27/2022]
Abstract
Classical galactosaemia is an autosomal recessive disease of galactose metabolism caused by a deficiency of the enzyme galactose-1-phosphate uridyltransferase (GALT). Galactosaemia is not included in the neonatal screening programme in Mexico and it is necessary to implement methodologies for prompt diagnosis of these patients to establish treatment. To date, more than 190 mutations in the GALT gene have been reported, most in caucasian populations, but there have been no reports of mutations in Latin-American populations. We report here the mutational spectrum in 19 Mexican galactosaemic patients. The most frequent mutations were p.Q188R, p.N314D and IVS2-2A>G, which together represented 71% of detected mutations. The mutation IVS2-2A>G, which has been detected only in Hispanics, was thought to generate a null allele; we identified one patient with a homozygous IVS2-2A>G mutation who showed a mild deficiency of enzyme value in erythrocytes. One patient homozygous for Duarte 2 (p.N314D, IVS5+62G>A) is probably due to a partial uniparental disomy of chromosome 9. In addition, a novel mutation c.336T>C (p.S112R) was detected in one patient with severe enzymatic deficiency. Despite the small number of patients studied, our results suggest that classical galactosaemia shows low allelic heterogeneity in Mexican patients, in contrast what is observed in other Mendelian disorders such as cystinosis or autosomal dominant hypercholesterolaemia. This low allelic heterogeneity might be explained by a "population of origin" effect in the central region of Mexico, as has been described for phenylketonuria.
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Affiliation(s)
- J Velázquez-Aragón
- Molecular Biology Laboratory, Genetics Department, Instituto Nacional de Pediatría, D.F., México
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16
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Zschocke J. Dominant versus recessive: molecular mechanisms in metabolic disease. J Inherit Metab Dis 2008; 31:599-618. [PMID: 18932014 DOI: 10.1007/s10545-008-1016-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2008] [Revised: 08/13/2008] [Accepted: 08/14/2008] [Indexed: 12/17/2022]
Abstract
Inborn errors of metabolism used to be regarded as simple monogenic traits, but a closer look at how different alleles of a gene determine different phenotypes shows that the molecular mechanisms in the individual case are often complicated. Most metabolic disorders represent a spectrum of phenotypes from normal via attenuated to severe (and sometimes prenatally fatal), and disease manifestation is often influenced by other specific genetic or exogenous factors. The terms 'dominant' or 'recessive' relate to the functional consequences of differing alleles in the (compound) heterozygous individual; the terms are irrelevant for homozygous individuals and inappropriate for X-linked disorders. Mutations affecting the same amino acid residue may be associated with different inheritance patterns. True dominant inheritance in metabolism is rare; it may be found e.g. in tightly regulated biosynthetic pathways or when minor changes in metabolite concentrations have a functional effect. Some disorders such as erythropoietic protoporphyria show pseudodominant inheritance due to prevalent loss-of-function polymorphisms in the general population and are better acknowledged as recessive traits. The term 'variable expressivity' is not helpful with regard to autosomal recessive disorders when variable phenotypes are explained by different mutations in the respective gene. Clonal unmasking of a heterozygous mutation through somatic loss of the second allele, the main pathomechanism in inherited tumour predisposition syndromes, is rare in metabolic disorders, but focal congenital hyperinsulinism is a notable exception. Somatic mosaicism for an OTC gene mutation is given as an example of an apparently heterozygous mutation pattern in a boy with an X-linked disease.
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Affiliation(s)
- Johannes Zschocke
- Institute of Human Genetics, Heidelberg University, Heidelberg, Germany.
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17
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Lukac Bajalo J, Mencej S, Karas N, Mlinar B, Zitnik IP, Gersak K. Q188R, K285N, and N314D mutation-associated alleles in the galactose-1-phosphate uridyltransferase gene and female infertility. Fertil Steril 2005; 83:776-8. [PMID: 15749517 DOI: 10.1016/j.fertnstert.2004.10.029] [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] [Received: 04/12/2004] [Revised: 10/14/2004] [Accepted: 10/14/2004] [Indexed: 12/01/2022]
Abstract
In a retrospective case-control study, the frequencies of Q188R, K285N, N314D, and IVS5-24G>A mutations were determined with the use of polymerase chain reaction and restriction fragment length polymorphism in the group of infertile women and the controls. No statistically significant differences were observed in the allele frequencies between the infertile women and control groups.
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Affiliation(s)
- Jana Lukac Bajalo
- Department of Clinical Biochemistry, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia.
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18
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Tighe O, Flanagan JM, Kernan F, O'Neill C, Naughten E, Mayne PD, Croke DT. Frequency distribution of the Los Angeles and Duarte galactose-1-phosphate uridyltransferase variant alleles in the Irish population. Mol Genet Metab 2004; 82:345-7. [PMID: 15308134 DOI: 10.1016/j.ymgme.2004.06.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2004] [Revised: 06/09/2004] [Accepted: 06/09/2004] [Indexed: 11/29/2022]
Abstract
Anonymous population screening was carried out to detect the N314D, Los Angeles (D1), and Duarte (D2) alleles of the galactose-1-phosphate uridyltransferase gene in Ireland using 743 blood samples, covering the Traveller (n = 243) and non-Traveller (n = 500) population groups. The frequency of the N314D substitution was found to be 0.099 overall. D1 allele frequencies were found to be 0.031 and 0.023 in the Traveller and non-Traveller groups, respectively, while D2 allele frequencies were 0.058 and 0.076, respectively. No significant differences in allele frequency were detected between the Traveller and non-Traveller groups, or between the Irish population groups and the literature values for Northern and Western Europe.
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Affiliation(s)
- Orna Tighe
- Department of Pathology, The Children's University Hospital, Temple Street, Dublin 1, Ireland
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19
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Lukac-Bajalo J, Marc J, Mlinar B, Karas N, Krzisnik C, Battelino T. Frequencies of Q188R and N314D mutations and IVS5-24g>A intron variation in the galactose-1-phosphate uridyl transferase (GALT) gene in the Slovenian population. Clin Chem Lab Med 2002; 40:1109-13. [PMID: 12521227 DOI: 10.1515/cclm.2002.194] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Numerous mutations in the galactose-1-phosphate uridyl transferase (GALT) gene have been found to impair GALT activity to different extent, causing galactosemia. This disorder exhibits considerable allelic heterogeneity in different populations and ethnic groups. The Q188R mutation accounts for 60-70% of classical galactosemia alleles in the Caucasian population. Individuals homoallelic for Q188R have a severe phenotype with complete loss of enzyme activity. Another form of GALT deficiency is Duarte galactosemia with N314D mutation associated alleles (Duarte-2). Although heterozygotes for classical galactosemia are asymptomatic at birth and Duarte galactosemia appears to be quite benign, there are some indications that these disorders can increase the risk of developing certain diseases later in life. The aim of our study was to analyze a healthy Slovenian population for the frequencies of Q188R and N314D mutations, and for the Duarte-2 indicative intronic variation IVS5-24G>A. DNA samples from 174 healthy subjects were analyzed for all three mutations by polymerase chain reaction and digestion with restriction enzymes. Allele frequencies for Q188R and N314D mutations and IVS5-24G>A intron variation were found to be 0.29%, 8.0% and 5.7%, respectively. These results correlate well with those reported for most other healthy Caucasian populations.
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Affiliation(s)
- Jana Lukac-Bajalo
- Department of Clinical Biochemistry, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia.
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20
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Elsas LJ, Webb AL, Langley SD. Characterization of a carbohydrate response element regulating the gene for human galactose-1-phosphate uridyltransferase. Mol Genet Metab 2002; 76:287-96. [PMID: 12208133 DOI: 10.1016/s1096-7192(02)00106-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Human galactose-1-phosphate uridyltransferase (hGALT) is a central enzyme in the conserved pathway by which galactose is converted to energy, UDP-galactose and UDP-glucose. A natural mutation that deleted -119 to -116 bp (delGTCA) of the promoter decreased hGALT mRNA and enzyme activity and prompted analysis of hGALT gene regulation. Regulatory domains were identified by inspection and confirmed in a reporter system. Previous studies by others were confirmed that HepG2 cells grown in D-glucose increased hGALT enzyme activity and mRNA by 30%. We extended these observations by sequencing the promoter region and identifying a potential carbohydrate response element (ChoRE). The response to glucose rose to 190% when a plasmid construct containing a luciferase reporter and only the -165 bp region as a promoter was transfected into HepG2 and NIH:OVCAR-3. By contrast, fibroblasts transfected with the identical construct failed to respond to glucose. Within the -165 bp region there were two enhancer (E-box) motifs that encompassed the delGTCA mutation. The deletion diminished the positive regulatory response, but an additional GTCA repeat unexpectedly increased the response. Using this postulated ChoRE as a probe in electrophoretic mobility shift assays, multiple nuclear proteins bound and one was identified as a member of the basic/helix-loop-helix/leucine zipper enhancer-binding (b/HLH/LZ) family. Increased binding of proteins correlated with increased hGALT expression when the spacing between E-box motifs was enlarged but the carbohydrate response was dampened. When the 3(')E-box was mutated, b/HLH/LZ binding and gene expression were abolished. We conclude that the hGALT promoter region contains a ChoRE in which the spacing between and the sequence of its E-box motifs are critical. One nuclear protein of the b/HLH/LZ family is necessary, but not sufficient for the carbohydrate response.
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Affiliation(s)
- Louis J Elsas
- Department of Pediatrics, Division of Medical Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA.
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