1
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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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2
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Cheng YHH, Bohaczuk SC, Stergachis AB. Functional categorization of gene regulatory variants that cause Mendelian conditions. Hum Genet 2024; 143:559-605. [PMID: 38436667 PMCID: PMC11078748 DOI: 10.1007/s00439-023-02639-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 12/30/2023] [Indexed: 03/05/2024]
Abstract
Much of our current understanding of rare human diseases is driven by coding genetic variants. However, non-coding genetic variants play a pivotal role in numerous rare human diseases, resulting in diverse functional impacts ranging from altered gene regulation, splicing, and/or transcript stability. With the increasing use of genome sequencing in clinical practice, it is paramount to have a clear framework for understanding how non-coding genetic variants cause disease. To this end, we have synthesized the literature on hundreds of non-coding genetic variants that cause rare Mendelian conditions via the disruption of gene regulatory patterns and propose a functional classification system. Specifically, we have adapted the functional classification framework used for coding variants (i.e., loss-of-function, gain-of-function, and dominant-negative) to account for features unique to non-coding gene regulatory variants. We identify that non-coding gene regulatory variants can be split into three distinct categories by functional impact: (1) non-modular loss-of-expression (LOE) variants; (2) modular loss-of-expression (mLOE) variants; and (3) gain-of-ectopic-expression (GOE) variants. Whereas LOE variants have a direct corollary with coding loss-of-function variants, mLOE and GOE variants represent disease mechanisms that are largely unique to non-coding variants. These functional classifications aim to provide a unified terminology for categorizing the functional impact of non-coding variants that disrupt gene regulatory patterns in Mendelian conditions.
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Affiliation(s)
- Y H Hank Cheng
- Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, WA, USA
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Stephanie C Bohaczuk
- Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, WA, USA
| | - Andrew B Stergachis
- Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, WA, USA.
- Department of Genome Sciences, University of Washington, Seattle, WA, USA.
- Brotman Baty Institute for Precision Medicine, Seattle, WA, USA.
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3
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Oh SL, Cheng LY, J Zhou JF, Henke W, Hagen T. Galactose 1-phosphate accumulates to high levels in galactose-treated cells due to low GALT activity and absence of product inhibition of GALK. J Inherit Metab Dis 2020; 43:529-539. [PMID: 31774565 DOI: 10.1002/jimd.12198] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 11/22/2019] [Accepted: 11/25/2019] [Indexed: 12/17/2022]
Abstract
Classic Galactosaemia is a genetic disorder, characterised by galactose intolerance in newborns. It occurs due to recessive mutations in the galactose-1-phosphate uridylyltransferase (GALT) gene. One of the main alterations caused by GALT deficiency is the accumulation of galactose 1-phosphate (Gal-1P) in cells. Studies have suggested that Gal-1P exerts cellular toxicity, possibly by inhibiting cellular metabolism. However, the exact significance of Gal-1P in disease pathogenesis remains unclear. In this study, we tested the hypothesis that Gal-1P inhibits cellular glucose utilisation by competing with substrates in the glycolytic pathway. We also investigated the metabolism of both galactose and glucose in GALT-expressing HEK293T and 143B cells to identify critical reactions steps contributing to the metabolic toxicity of galactose. Notably, we found that galactose-treated HEK293T and 143B cells, which express endogenous GALT, accumulate markedly high intracellular Gal-1P concentrations. Despite very high intracellular Gal-1P concentrations, no inhibition of cellular glucose uptake and no significant changes in the intracellular concentrations of glycolytic metabolites were observed. This indicates that Gal-1P does not exert an inhibitory effect on glycolysis in cells and rules out one potential hypothesis for cellular Gal-1P toxicity. We also investigated the mechanism responsible for the observed Gal-1P accumulation. Our results suggest that Gal-1P accumulation is a result of both low GALT activity and the absence of product inhibition by Gal-1P on galactokinase (GALK1), the enzyme responsible for phosphorylating galactose to Gal-1P. These findings provide a better understanding of the disease mechanisms underlying Classic Galactoaemia.
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Affiliation(s)
- Sher Li Oh
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Li Yi Cheng
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Jie Fu J Zhou
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Wolfgang Henke
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Thilo Hagen
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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4
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Abramicheva PA, Balakina TA, Morozov IA, Schelkunova TA, Smirnova OV. Prolactin Signaling Pathways Determining Its Direct Effects on Kidneys in the Cholestasis of Pregnancy Model. BIOCHEMISTRY (MOSCOW) 2019; 84:1204-1212. [DOI: 10.1134/s0006297919100092] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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5
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Papachristoforou R, Petrou PP, Sawyer H, Williams M, Drousiotou A. Classic galactosaemia in the Greek Cypriot population: An epidemiological and molecular study. Ann Hum Genet 2019; 83:291-298. [PMID: 30994193 PMCID: PMC6766971 DOI: 10.1111/ahg.12318] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 03/15/2019] [Accepted: 03/25/2019] [Indexed: 11/27/2022]
Abstract
Classic galactosaemia is an inherited metabolic disorder of galactose metabolism caused by deficiency of the enzyme galactose-1-phosphate uridyltransferase (GALT) resulting from mutations in the GALT gene. The objectives of the present study were the determination of the carrier frequency of classic galactosaemia in the Greek Cypriot population and the molecular characterization of the disease alleles. We performed an epidemiological study involving 528 Greek Cypriots originating from all parts of Cyprus. Carriers were identified by measuring GALT activity in red blood cells and were subsequently subjected to mutation analysis. A total of five mutations were identified in patients and carriers of classic galactosaemia: a large deletion of 8.5 kb previously reported by us (55% of alleles), the known mutations p.Lys285Asn (30%), p.Pro185Ser (5%), and c.820+13A>G (5%), and a novel mutation c.378-12G>A (5%). Interestingly, the most common mutation in European populations, p.Gln188Arg, was not identified in this Cypriot cohort. The carrier frequency for classic galactosaemia among Greek Cypriots was estimated to be 1:88, predicting a homozygote incidence of 1:31,000 births. The Duarte 1 and Duarte 2 variants were found to be present at a frequency of 5.5% and 2.5%, respectively.
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Affiliation(s)
- Rena Papachristoforou
- Department of Biochemical Genetics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
| | - Petros P Petrou
- Department of Biochemical Genetics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus.,The Cyprus School of Molecular Medicine, Nicosia, Cyprus
| | - Hilary Sawyer
- Bristol Genetics Laboratory, Southmead Hospital, Bristol, United Kingdom
| | - Maggie Williams
- Bristol Genetics Laboratory, Southmead Hospital, Bristol, United Kingdom
| | - Anthi Drousiotou
- Department of Biochemical Genetics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus.,The Cyprus School of Molecular Medicine, Nicosia, Cyprus
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6
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Wang NK, Chiang JPW. Increasing evidence of combinatory variant effects calls for revised classification of low-penetrance alleles. Genet Med 2018; 21:1280-1282. [PMID: 30385887 PMCID: PMC6752265 DOI: 10.1038/s41436-018-0347-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 10/15/2018] [Indexed: 11/09/2022] Open
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7
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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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8
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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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9
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Winter GN, Ben-Pazi H. Neurologic sequela in a patient with galactosemia potentially mediated by interleukin-11 dysfunction. J Child Neurol 2015; 30:922-6. [PMID: 25008910 DOI: 10.1177/0883073814540520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 05/22/2014] [Indexed: 11/16/2022]
Abstract
A 16-year-old galactosemic patient, homozygous for the 5.5-kb gene deletion, suffered severe neurologic regression following streptococcal infection. Since the gene deletion includes the promoter of interleukin-11a receptor involved in neuronal apoptosis, we questioned whether this patient had no interleukin-11a receptor activity-resulting in neuronal toxicity during septicemia. We hypothesized that interleukin-11 levels would be elevated because of a loss of feedback induced by the absent interleukin-11Ra receptor complex. To assess this, we compared interleukin-11 levels in the proband and 2 of his siblings with the same genetic deletion, to age-matched controls. No differences were found in interleukin-11 levels between groups. Our study was not carried out during acute infective states, when the disrupted immunoregulation triggered by sepsis is relevant, and is thus limited. In conclusion, although interleukin-11 was not chronically elevated in individuals with galactosemia and 5.5-kb gene deletion, data do not rule out potential interleukin-11 dysfunction during acute infection.
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Affiliation(s)
- Gidon N Winter
- Pediatric Movement Disorders, Neuropediatric Unit, Shaare Zedek Medical Center, Jerusalem, Israel
| | - Hilla Ben-Pazi
- Pediatric Movement Disorders, Neuropediatric Unit, Shaare Zedek Medical Center, Jerusalem, Israel
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10
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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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12
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Functional correction by antisense therapy of a splicing mutation in the GALT gene. Eur J Hum Genet 2014; 23:500-6. [PMID: 25052314 DOI: 10.1038/ejhg.2014.149] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2013] [Revised: 06/24/2014] [Accepted: 06/28/2014] [Indexed: 12/24/2022] Open
Abstract
In recent years, antisense therapy has emerged as an increasingly important therapeutic approach to tackle several genetic disorders, including inborn errors of metabolism. Intronic mutations activating cryptic splice sites are particularly amenable to antisense therapy, as the canonical splice sites remain intact, thus retaining the potential for restoring constitutive splicing. Mutational analysis of Portuguese galactosemic patients revealed the intronic variation c.820+13A>G as the second most prevalent mutation, strongly suggesting its pathogenicity. The aim of this study was to functionally characterize this intronic variation, to elucidate its pathogenic molecular mechanism(s) and, ultimately, to correct it by antisense therapy. Minigene splicing assays in two distinct cell lines and patients' transcript analyses showed that the mutation activates a cryptic donor splice site, inducing an aberrant splicing of the GALT pre-mRNA, which in turn leads to a frameshift with inclusion of a premature stop codon (p.D274Gfs*17). Functional-structural studies of the recombinant wild-type and truncated GALT showed that the latter is devoid of enzymatic activity and prone to aggregation. Finally, two locked nucleic acid oligonucleotides, designed to specifically recognize the mutation, successfully restored the constitutive splicing, thus establishing a proof of concept for the application of antisense therapy as an alternative strategy for the clearly insufficient dietary treatment in classic galactosemia.
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13
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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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15
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Coelho AI, Ramos R, Gaspar A, Costa C, Oliveira A, Diogo L, Garcia P, Paiva S, Martins E, Teles EL, Rodrigues E, Cardoso MT, Ferreira E, Sequeira S, Leite M, Silva MJ, de Almeida IT, Vicente JB, Rivera I. A frequent splicing mutation and novel missense mutations color the updated mutational spectrum of classic galactosemia in Portugal. J Inherit Metab Dis 2014; 37:43-52. [PMID: 23749220 DOI: 10.1007/s10545-013-9623-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 05/16/2013] [Accepted: 05/17/2013] [Indexed: 01/28/2023]
Abstract
Classic galactosemia is an autosomal recessive disorder caused by deficient galactose-1-phosphate uridylyltransferase (GALT) activity. Patients develop symptoms in the neonatal period, which can be ameliorated by dietary restriction of galactose. Many patients develop long-term complications, with a broad range of clinical symptoms whose pathophysiology is poorly understood. The high allelic heterogeneity of GALT gene that characterizes this disorder is thought to play a determinant role in biochemical and clinical phenotypes. We aimed to characterize the mutational spectrum of GALT deficiency in Portugal and to assess potential genotype-phenotype correlations. Direct sequencing of the GALT gene and in silico analyses were employed to evaluate the impact of uncharacterized mutations upon GALT functionality. Molecular characterization of 42 galactosemic Portuguese patients revealed a mutational spectrum comprising 14 nucleotide substitutions: ten missense, two nonsense and two putative splicing mutations. Sixteen different genotypic combinations were detected, half of the patients being p.Q188R homozygotes. Notably, the second most frequent variation is a splicing mutation. In silico predictions complemented by a close-up on the mutations in the protein structure suggest that uncharacterized missense mutations have cumulative point effects on protein stability, oligomeric state, or substrate binding. One splicing mutation is predicted to cause an alternative splicing event. This study reinforces the difficulty in establishing a genotype-phenotype correlation in classic galactosemia, a monogenic disease whose complex pathogenesis and clinical features emphasize the need to expand the knowledge on this "cloudy" disorder.
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Affiliation(s)
- Ana I Coelho
- Metabolism & Genetics Group, Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon, Av. Prof. Gama Pinto, 1643-009, Lisbon, Portugal
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16
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Galactosemia in the Turkish population with a high frequency of Q188R mutation and distribution of Duarte-1 and Duarte-2 variations. J Hum Genet 2013; 58:675-8. [DOI: 10.1038/jhg.2013.76] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 06/04/2013] [Accepted: 07/01/2013] [Indexed: 11/08/2022]
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Boutron A, Marabotti A, Facchiano A, Cheillan D, Zater M, Oliveira C, Costa C, Labrune P, Brivet M. Mutation spectrum in the French cohort of galactosemic patients and structural simulation of 27 novel missense variations. Mol Genet Metab 2012; 107:438-47. [PMID: 22944367 DOI: 10.1016/j.ymgme.2012.07.025] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Revised: 07/31/2012] [Accepted: 07/31/2012] [Indexed: 11/20/2022]
Abstract
BACKGROUND Classic galactosemia refers to galactose-1-phosphate uridyltransferase (GALT) deficiency and is characterized by long-term complications of unknown mechanism and high allelic heterogeneity of GALT gene. AIM To report molecular characterization of GALT variations in 210 French families, to analyze the structural effects of novel missense variations and to assess informativity of structural data in predicting outcome. METHODS Sequencing of exons and intron-exon junctions of GALT gene was completed in unsolved cases by analysis of a long range PCR product. Structural consequences of novel missense variations were predicted using a homology model of GALT protein and a semi-automated analysis which integrates simulation of variations, structural analyses and two web servers dedicated to identify mutation-induced change of protein stability. RESULTS Forty four novel variations were identified, among them 27 nucleotide substitutions. In silico modeling of these missense variations showed that 12 variations are predicted to impair subunit interactions and/or active site conformation and that 23 variations modify H-bond or salt-bridge networks. Twenty variations decrease the global stability of the protein. Five variations had apparently no structural effect. CONCLUSION Our results expand the mutation spectrum in GALT gene and the list of GALT variations analyzed at the structural level, providing new data to assess the pathophysiology of galactosemia.
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Affiliation(s)
- Audrey Boutron
- Biochimie - Hôpital de Bicêtre, Hôpitaux Universitaires Paris-Sud, APHP-Paris, France.
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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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Solomon BD, Pineda-Alvarez DE, Bear KA, Mullikin JC, Evans JP. Applying Genomic Analysis to Newborn Screening. Mol Syndromol 2012; 3:59-67. [PMID: 23112750 DOI: 10.1159/000341253] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/06/2012] [Indexed: 01/30/2023] Open
Abstract
Large-scale genomic analysis such as whole-exome and whole-genome sequencing is becoming increasingly prevalent in the research arena. Clinically, many potential uses of this technology have been proposed. One such application is the extension or augmentation of newborn screening. In order to explore this application, we examined data from 3 children with normal newborn screens who underwent whole-exome sequencing as part of research participation. We analyzed sequence information for 151 selected genes associated with conditions ascertained by newborn screening. We compared findings with publicly available databases and results from over 500 individuals who underwent whole-exome sequencing at the same facility. Novel variants were confirmed through bidirectional dideoxynucleotide sequencing. High-density microarrays (Illumina Omni1-Quad) were also performed to detect potential copy number variations affecting these genes. We detected an average of 87 genetic variants per individual. After excluding artifacts, 96% of the variants were found to be reported in public databases and have no evidence of pathogenicity. No variants were identified that would predict disease in the tested individuals, which is in accordance with their normal newborn screens. However, we identified 6 previously reported variants and 2 novel variants that, according to published literature, could result in affected offspring if the reproductive partner were also a mutation carrier; other specific molecular findings highlight additional means by which genomic testing could augment newborn screening.
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Affiliation(s)
- B D Solomon
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Md., USA
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Berry GT, Elsas LJ. Introduction to the Maastricht workshop: lessons from the past and new directions in galactosemia. J Inherit Metab Dis 2011; 34:249-55. [PMID: 21116719 DOI: 10.1007/s10545-010-9232-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Revised: 09/29/2010] [Accepted: 10/07/2010] [Indexed: 11/25/2022]
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Ovarian tissue cryopreservation and subsequent spontaneous pregnancies in a patient with classic galactosemia. Fertil Steril 2011; 95:290.e1-3. [PMID: 20663501 DOI: 10.1016/j.fertnstert.2010.06.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2010] [Revised: 06/04/2010] [Accepted: 06/07/2010] [Indexed: 11/21/2022]
Abstract
OBJECTIVE To report two consecutive spontaneous pregnancies in a compound heterozygous patient with classic galactosemia and a heterozygous partner, 6 years after ovarian tissue cryopreservation. DESIGN Case report. SETTING Tertiary health care center. PATIENT(S) A patient with classic galactosemia and strict adherance to a galactose-free diet. INTERVENTION(S) Right ovariectomy by laparoscopy and cryopreservation of cortical slices; metabolic follow-up. MAIN OUTCOME MEASURE(S) Genotyping, galactose-1-phosphate uridyltransferase (GALT) activity and erythrocyte galactose-1-phosphate determination, histology of ovarian cortex, pregnancy achievement. RESULT(S) Undetectable GALT activity; compound heterozygosity: association of c.563A>G (p.Gln188Arg) and a novel mutation c.982C>T (p.Arg328Cys); rare growing follicles and abnormally low primordial follicles; two uneventful spontaneous pregnancies without need for autografting of the cryopreserved tissue. CONCLUSION(S) The risk for ovarian failure is a frequent concern, but spontaneous pregnancies may occur, even repeatedly, in young patients with galactosemia. Thus, there is a need for more accurate predictive factors to guide the indication for ovarian tissue cryopreservation, the benefits and risks of which have to be balanced through a multidisciplinary approach.
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Abstract
In most organisms, productive utilization of galactose requires the highly conserved Leloir pathway of galactose metabolism. Yet, if this metabolic pathway is perturbed due to congenital deficiencies of the three associated enzymes, or an overwhelming presence of galactose, this monosaccharide which is abundantly present in milk and many non-dairy foodstuffs, will become highly toxic to humans and animals. Despite more than four decades of intense research, little is known about the molecular mechanisms of galactose toxicity in human patients and animal models. In this contemporary review, we take a unique approach to present an overview of galactose toxicity resulting from the three known congenital disorders of galactose metabolism and from experimental hypergalactosemia. Additionally, we update the reader about research progress on animal models, as well as advances in clinical management and therapies of these disorders.
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Affiliation(s)
- Kent Lai
- Division of Medical Genetics, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
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Rubio-Gozalbo ME, Gubbels CS, Bakker JA, Menheere PPCA, Wodzig WKWH, Land JA. Gonadal function in male and female patients with classic galactosemia. Hum Reprod Update 2009; 16:177-88. [PMID: 19793842 DOI: 10.1093/humupd/dmp038] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Hypergonadotropic hypoestrogenic infertility is the most burdensome complication for females suffering from classic galactosemia. In contrast, male gonadal function seems less affected. The underlying mechanism is not understood and several pathogenic mechanisms have been proposed. Timing of the lesion, prenatal or chronic post-natal, or a combination of both are not yet clear. METHODS This review focuses on gonadal function in males and females, ovarian imaging and histology in this disease. It is based on the literature known to the authors and a Pubmed search using the keywords galactosemia, GALT deficiency, (premature) ovarian failure/insufficiency/dysfunction, testicular function, gonadotrophins, FSH, LH (published between January 1971 and April 2009). RESULTS Male gonads are less affected, boys spontaneously reach puberty, although onset can be delayed. Semen quality has not been extensively studied. Several affected males are known to have fathered a child. Female gonads are invariably affected, although to a varied extent (hypergonadotropic hypoestrogenic ovarian dysfunction). Intriguingly, FSH is often already increased in infancy. Imaging usually shows hypoplastic and streak-like ovaries. Histological findings in some cases reveal the presence of morphologically normal but decreased numbers of primordial follicles, with the absence of intermediate and Graafian follicles. CONCLUSION Gonads in males seem less affected than in females who exhibit hypergonadotropic hypoestrogenic subfertility. FSH can be elevated in infancy, and ovarian histology sometimes shows the presence of normal primordial follicles with absence of intermediate and Graafian follicles. These findings are similar to other genetic diseases primarily affecting the ovary.
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Affiliation(s)
- M E Rubio-Gozalbo
- Department of Pediatrics, Maastricht University Medical Center, Maastricht, The Netherlands.
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25
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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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Park HD, Kim YK, Park KU, Kim JQ, Song YH, Song J. A novel c.-22T>C mutation in GALK1 promoter is associated with elevated galactokinase phenotype. BMC MEDICAL GENETICS 2009; 10:29. [PMID: 19309526 PMCID: PMC2667498 DOI: 10.1186/1471-2350-10-29] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Accepted: 03/24/2009] [Indexed: 11/10/2022]
Abstract
Background Many genetic variations of GALK1 have been identified in the patients with galactokinase (GALK1) deficiency. However, the molecular characteristics of GALK1 in individuals with elevated GALK1 activity are relatively unknown. Methods We investigated the relationship between elevated GALK1 activity and the molecular GALK1 gene variations, and the molecular mechanism underlying elevated GALK1 activity. PCR products from 63 subjects, without any attenuation of galactose degradation enzymes, were sequenced to screen for nucleotide alterations in the GALK1 promoter. Results Three nucleotide substitutions were identified: c.-179A>G, c.-27A>C, and c.-22T>C. With respect to the c.-22T>C mutation, GALK1 activity in 13 subjects with the T/C or C/C genotype was significantly higher than those in 50 subjects with the T/T genotype (p < 0.001). The dual luciferase reporter assay in Hep3B cells showed that the luciferase activity with the GALK1 promoter with the c.-22C mutant allele increased approximately 2.5-fold, compared to that with the c.-22T. A specific DNA-protein complex was observed in an electrophoretic mobility shift assay, with slightly higher affinity to c.-22C than to c.-22T. Conclusion The c.-22T>C mutation, which was observed frequently in individuals with elevated GALK1 activity, increased the expression of a reporter gene through enhanced binding of a currently unidentified nuclear protein. These results suggest that the elevated GALK1 activity resulted from enhanced gene expression, due to nucleotide variation within GALK1 promoter.
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Affiliation(s)
- Hyung-Doo Park
- Ilsong Institute of Life Science, Hallym University, Anyang, Korea.
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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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Barbouth DS, Velazquez DL, Konopka S, Wilkinson JJD, Carver VH, Elsas LJ. Screening newborns for galactosemia using total body galactose oxidation to CO2 in expired air. Pediatr Res 2007; 62:720-4. [PMID: 17957157 DOI: 10.1203/pdr.0b013e3181598cdf] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Classic galactosemia is caused by impaired galactose-1-phosphate uridyltransferase (GALT EC 2.7.712). If discovered and treated within the first days of life, the acute problems of hepatocellular damage, sepsis, and death are prevented. However, chronic problems such as ataxia, tremor, dyspraxic speech, and ovarian failure may occur. To determine whether screening newborns before discharge from the nursery for GALT deficiency is feasible and whether acute and chronic signs could be prevented by earlier intervention, we developed a simplified "breath test." We quantitated total body oxidation of C-D-galactose to CO2 in expired air by normal newborns between 2 h and 2 mo of age and compared their results to older children with GALT deficiency. We found no differences in total body galactose oxidation (TBGO) among normal newborns up to 48 h of age, but a 2-fold rise in TBGO developed during their first 2 wk of life. Older children with galactosemia had significantly less oxidative capacity than normal newborns. We conclude that newborn breath testing for total body galactose oxidation is feasible before discharge from nursery. It has potential utility for both preventing acute neonatal toxicity and determining the mechanisms producing long-term complications such as ovarian failure, dyspraxia, ataxia, and tremors.
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Affiliation(s)
- Deborah S Barbouth
- Department of Pediatrics, University of Miami, Miami, Florida 33136, USA
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29
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Jama M, Nelson L, Pont-Kingdon G, Mao R, Lyon E. Simultaneous amplification, detection, and analysis of common mutations in the galactose-1-phosphate uridyl transferase gene. J Mol Diagn 2007; 9:618-23. [PMID: 17884932 PMCID: PMC2049049 DOI: 10.2353/jmoldx.2007.070027] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Classic galactosemia is an autosomal recessive inherited error of galactose metabolism. It is caused by lack of galactose-1-phosphate uridyl transferase, an enzyme that is required to metabolize galactose-1-phosphate to uridine diphosphate galactose. The build up of galactose-1-phosphate is toxic at high levels and can damage the liver, brain, eyes, and other vital organs. Over 200 mutations have been identified in affected individuals. We describe an assay to identify nine target mutations or variants in the galactose-1-phosphate uridyl transferase gene, namely p.Q188R, p.S135L, p.K285N, p.L195P, p.T138M, p.Y209C, IVS2-2 A>G, p.L218L, and p.N314D. A single long-range PCR is followed by a multiplexed nucleotide extension assay (single nucleotide extension) and capillary electrophoresis to detect simultaneously all nine target mutations/variants. Fifty-four previously characterized samples (47 clinical samples and seven controls) gave a 100% concordance. We also report a nontarget novel mutation, p.L192X, and its profile using single nucleotide extension. This assay can complement the enzyme activity assay and identify familial mutations for testing additional family members.
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Affiliation(s)
- Mohamed Jama
- ARUP Institute for Clinical and Experimental Pathology, 500 Chipeta Way, Salt Lake City, UT 84108, USA
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30
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Abstract
Classical galactosaemia (McKusick 230400) is an: autosomal recessive disorder of galactose metabolism, caused by a deficiency of the enzyme galactose-1-phosphate uridyltransferase (GALT; EC 2.7.712). Most patients present in the neonatal period, after ingestion of galactose, with jaundice, hepatosplenomegaly, hepatocellular insufficiency, food intolerance, hypoglycaemia, renal tubular dysfunction, muscle hypotonia, sepsis and cataract. The gold standard for diagnosis of classical galactosaemia is measurement of GALT activity in erythrocytes. Gas-chromatographic determination of urinary sugars and sugar alcohols demonstrates elevated concentrations of galactose and galactitol. The only therapy for patients with classical galactosaemia is a galactose-restricted diet, and initially all galactose must be removed from the diet as soon as the diagnosis is suspected. After the neonatal period, a lactose-free diet is advised in most countries, without restriction of galactose-containing fruit and vegetables. In spite of the strict diet, long-term complications such as retarded mental development, verbal dyspraxia, motor abnormalities and hypergonadotrophic hypogonadism are frequently seen in patients with classical galactosaemia. It has been suggested that these complications may result from endogenous galactose synthesis or from abnormal galactosylation. Novel therapeutic strategies, aiming at the prevention of galactose 1-phosphate production, should be developed. In the meantime, the follow-up protocol for patients with GALT deficiency should focus on early detection, evaluation and, if possible, early intervention in problems of motor, speech and cognitive development.
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Affiliation(s)
- Annet M Bosch
- Department of Pediatrics, Division of Metabolic Disorders, Academic Medical Centre (G8 205), University Hospital of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
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Forges T, Monnier-Barbarino P, Leheup B, Jouvet P. Pathophysiology of impaired ovarian function in galactosaemia. Hum Reprod Update 2006; 12:573-84. [PMID: 16835432 DOI: 10.1093/humupd/dml031] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Classical galactosaemia is an inherited inborn error of the major galactose assimilation pathway, caused by galactose-1-phosphate uridyltransferase (GALT) deficiency. Many GALT mutations have been described, with different clinical consequences. In severe forms, newborns present with a life-threatening, acute toxic syndrome that rapidly regresses under a galactose-restricted diet. However, long-term complications, particularly cognitive and motor abnormalities, as well as hypergonadotrophic hypogonadism in female patients are still unavoidable. The pathogenesis of galactose-induced ovarian toxicity remains unclear but probably involves galactose itself and its metabolites such as galactitol and UDP-galactose. Possible mechanisms of ovarian damage include direct toxicity of galactose and metabolites, deficient galactosylation of glycoproteins and glycolipids, oxidative stress and activation of apoptosis. As there is no aetiological treatment, clinical management of ovarian failure in galactosaemic patients principally relies on hormonal replacement therapy to induce pubertal development and to prevent bone loss and other consequences of estrogen deprivation. Further investigations will be necessary to better understand the metabolic flux of galactose through its biochemical pathways and the mechanisms of these secondary complications. The aim of this article is to present an extensive review on the pathogenesis and clinical management of galactose-induced premature ovarian failure.
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Affiliation(s)
- T Forges
- Department of Reproductive Medicine, Maternité Régionale Universitaire, Nancy Cedex, France.
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Larsson SC, Orsini N, Wolk A. Milk, milk products and lactose intake and ovarian cancer risk: a meta-analysis of epidemiological studies. Int J Cancer 2006; 118:431-41. [PMID: 16052536 DOI: 10.1002/ijc.21305] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
It has been proposed, on the basis of animal models and ecological studies, that consumption or metabolism of dairy sugar may increase the risk of ovarian cancer. Case-control and cohort studies of the association between lactose and dairy food consumption and ovarian cancer risk, however, have yielded varied findings. We summarized the available literature on this topic using a meta-analytic approach. Random-effects models were used to estimate the summary relative risks (RR(summary)). A linear regression analysis of the natural logarithm of the RR was carried out to assess a possible dose-response relationship between lactose intake and ovarian cancer risk. Eighteen case-control and 3 prospective cohort studies were eligible for inclusion in the meta-analysis. The findings of case-control studies were heterogeneous, and, except for whole milk (RR(summary) for highest vs. lowest category = 1.27, 95% confidence interval [CI] = 0.97-1.68), do not provide evidence of positive associations between dairy food and lactose intakes with risk of ovarian cancer. In contrast, the 3 cohort studies are consistent and show significant positive associations between intakes of total dairy foods, low-fat milk, and lactose and risk of ovarian cancer. The RR(summary) for a daily increase of 10 g in lactose intake (the approximate amount in 1 glass of milk) was 1.13 (95% CI = 1.05-1.22) for cohort studies. In conclusion, prospective cohort studies, but not case-control studies, support the hypothesis that high intakes of dairy foods and lactose may increase the risk of ovarian cancer.
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Affiliation(s)
- Susanna C Larsson
- Division of Nutritional Epidemiology, The National Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
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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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Scaglia F, Vogel H, Hawkins EP, Vladutiu GD, Liu LL, Wong LJC. Novel homoplasmic mutation in the mitochondrialtRNATyr gene associated with atypical mitochondrial cytopathy presenting with focal segmental glomerulosclerosis. ACTA ACUST UNITED AC 2003; 123A:172-8. [PMID: 14598342 DOI: 10.1002/ajmg.a.20315] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We report a 9-year-old girl with a mitochondrial cytopathy preceded by steroid-resistant focal segmental glomerulosclerosis (FSGS). The proband presented at the age of 2 years with steroid-resistant nephrotic syndrome caused by FSGS. Her renal function progressively deteriorated and a dilated cardiomyopathy developed at the age of 7 years. A skeletal muscle biopsy showed a combined respiratory chain (RC) defect and a partial deficiency of coenzyme Q(10). A novel mutation in the evolutionary highly conserved region of the mitochondrial tRNA(Tyr) gene was found in homoplasmic state in skeletal muscle, blood, and renal tissue. The mutation was also found in homoplasmic state in her mildly symptomatic mother. No other maternal family members were available for testing. The present case of mitochondrial cytopathy initially presenting with steroid-resistant nephrotic syndrome, unusual biochemical and renal findings associated with a novel tRNA point mutation suggests that steroid-resistant FSGS can predate other features of mitochondrial disease for a prolonged period of time and that the progressive glomerulopathy associated with combined mitochondrial RC defects is genetically heterogeneous.
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MESH Headings
- Abnormalities, Multiple/genetics
- Base Sequence
- Biopsy
- Child
- Child, Preschool
- Chromatography, High Pressure Liquid
- Coenzymes
- DNA, Mitochondrial/genetics
- Female
- Glomerulosclerosis, Focal Segmental/genetics
- Glomerulosclerosis, Focal Segmental/pathology
- Humans
- Immunohistochemistry
- Kidney/ultrastructure
- Microscopy, Electron
- Mitochondrial Diseases/genetics
- Molecular Sequence Data
- Muscle, Skeletal/ultrastructure
- Mutation/genetics
- RNA, Transfer/genetics
- Sequence Alignment
- Sequence Analysis, DNA
- Tyrosine
- Ubiquinone/analogs & derivatives
- Ubiquinone/genetics
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Affiliation(s)
- Fernando Scaglia
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA.
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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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