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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Succoio M, Sacchettini R, Rossi A, Parenti G, Ruoppolo M. Galactosemia: Biochemistry, Molecular Genetics, Newborn Screening, and Treatment. Biomolecules 2022; 12:biom12070968. [PMID: 35883524 PMCID: PMC9313126 DOI: 10.3390/biom12070968] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 07/02/2022] [Accepted: 07/08/2022] [Indexed: 12/16/2022] Open
Abstract
Galactosemia is an inborn disorder of carbohydrate metabolism characterized by the inability to metabolize galactose, a sugar contained in milk (the main source of nourishment for infants), and convert it into glucose, the sugar used by the body as the primary source of energy. Galactosemia is an autosomal recessive genetic disease that can be diagnosed at birth, even in the absence of symptoms, with newborn screening by assessing the level of galactose and the GALT enzyme activity, as GALT defect constitutes the most frequent cause of galactosemia. Currently, galactosemia cannot be cured, but only treated by means of a diet with a reduced content of galactose and lactose. Although the diet is able to reverse the neonatal clinical picture, it does not prevent the development of long-term complications. This review provides an overview of galactose metabolism, molecular genetics, newborn screening and therapy of galactosemia. Novel treatments for galactosemia currently being investigated in (pre)clinical studies and potentially able to prevent long-term complications are also presented.
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Affiliation(s)
- Mariangela Succoio
- CEINGE-Biotecnologie Avanzate s.c.ar.l., 80145 Naples, Italy; (M.S.); (R.S.)
| | - Rosa Sacchettini
- CEINGE-Biotecnologie Avanzate s.c.ar.l., 80145 Naples, Italy; (M.S.); (R.S.)
| | - Alessandro Rossi
- Department of Translational Medical Sciences, University of Naples Federico II, 80131 Naples, Italy; (A.R.); (G.P.)
| | - Giancarlo Parenti
- Department of Translational Medical Sciences, University of Naples Federico II, 80131 Naples, Italy; (A.R.); (G.P.)
- Telethon Institute of Genetics and Medicine (TIGEM), 80078 Pozzuoli, Italy
| | - Margherita Ruoppolo
- CEINGE-Biotecnologie Avanzate s.c.ar.l., 80145 Naples, Italy; (M.S.); (R.S.)
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, 80131 Naples, Italy
- Correspondence:
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3
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Ohlsson A, Hunt M, Wedell A, von Döbeln U. Heterogeneity of disease-causing variants in the Swedish galactosemia population: Identification of 16 novel GALT variants. J Inherit Metab Dis 2019; 42:1008-1018. [PMID: 31194895 DOI: 10.1002/jimd.12136] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 06/10/2019] [Accepted: 06/11/2019] [Indexed: 11/11/2022]
Abstract
The aim was to determine disease-causing variants in the GALT gene which codes for the enzyme galactose-1-phosphate uridylyltransferase. Loss of activity of this enzyme causes classical galactosemia-a life threatening, treatable disorder, included in the Swedish newborn screening program since 1967. A total of 66 patients with the disease are known in Sweden and 56 index patients were investigated. An additional two patients with Duarte galactosemia were included. The disease-causing variants were identified in all patients. As reported from other countries only a few variants frequently recur in severe disease. The two variants p.(Gln188Arg) (c.563A>G) and p.(Met142Lys) (c.425T>A) are present in several index patients whereas the remaining are found in one to three patients each. The most common variant, p.(Gln188Arg), has an allele frequency of 51% in the cohort. A total of 16 novel variants were found among the 33 different variants in the cohort. Two of these are synonymous variants affecting splicing, demonstrating the importance of the evaluation of synonymous variants at the cDNA level. Concise sentence: Galactosemia is a rare disease in Sweden and the disease-causing variants are heterogenous including two synonymous variants.
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Affiliation(s)
- Annika Ohlsson
- Centre for Inherited Metabolic Diseases (CMMS), Karolinska University Hospital, Stockholm, Sweden
- Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden
| | - Mary Hunt
- The School of Biological and Health Sciences, Dublin Institute of Technology, Dublin, Ireland
| | - Anna Wedell
- Centre for Inherited Metabolic Diseases (CMMS), Karolinska University Hospital, Stockholm, Sweden
- Department of Molecular Medicine and Surgery, Karolinska Institute, Stockholm, Sweden
| | - Ulrika von Döbeln
- Centre for Inherited Metabolic Diseases (CMMS), Karolinska University Hospital, Stockholm, Sweden
- Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden
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4
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Yuzyuk T, Balakrishnan B, Schwarz EL, De Biase I, Hobert J, Longo N, Mao R, Lai K, Pasquali M. Effect of genotype on galactose-1-phosphate in classic galactosemia patients. Mol Genet Metab 2018; 125:258-265. [PMID: 30172461 DOI: 10.1016/j.ymgme.2018.08.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 08/21/2018] [Accepted: 08/22/2018] [Indexed: 11/27/2022]
Abstract
Impaired activity of galactose-1-phosphate uridyltransferase (GALT) causes classic galactosemia (OMIM 230400), characterized by the accumulation of galactose-1-phosphate (GAL1P) in patients' red blood cells (RBCs). Our recent study demonstrated a correlation between RBC GAL1P and long-term outcomes in galactosemia patients. Here, we analyze biochemical and molecular results in 77 classic galactosemia patients to evaluate the association between GALT genotypes and GAL1P concentration in RBCs. Experimental data from model organisms were also included to assess the correlation between GAL1P and predicted residual activity of each genotype. Although all individuals in this study showed markedly reduced RBC GALT activity, we observed significant differences in RBC GAL1P concentrations among galactosemia genotypes. While levels of GAL1P on treatment did not correlate with RBC GALT activities (p = 0.166), there was a negative nonlinear correlation between mean GAL1P concentrations and predicted residual enzyme activity of genotype (p = 0.004). These studies suggest that GAL1P levels in RBCs on treatment likely reflect the overall functional impairment of GALT in patients with galactosemia.
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Affiliation(s)
- Tatiana Yuzyuk
- Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, Salt Lake City, UT, USA.
| | - Bijina Balakrishnan
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, UT, USA
| | | | - Irene De Biase
- Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, Salt Lake City, UT, USA
| | - Judith Hobert
- Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, Salt Lake City, UT, USA
| | - Nicola Longo
- Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, Salt Lake City, UT, USA; Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, UT, USA
| | - Rong Mao
- Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, Salt Lake City, UT, USA
| | - Kent Lai
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, UT, USA
| | - Marzia Pasquali
- Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, Salt Lake City, UT, USA
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5
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Demirbas D, Coelho AI, Rubio-Gozalbo ME, Berry GT. Hereditary galactosemia. Metabolism 2018; 83:188-196. [PMID: 29409891 DOI: 10.1016/j.metabol.2018.01.025] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 01/19/2018] [Accepted: 01/24/2018] [Indexed: 10/18/2022]
Abstract
Hereditary galactosemia is an inborn error of carbohydrate metabolism. Galactose is metabolized by Leloir pathway enzymes; galactokinase (GALK), galactose-1-phosphate uridylyltransferase (GALT) and UDP-galactose 4-epimerase (GALE). The defects in these enzymes cause galactosemia in an autosomal recessive manner. The severe GALT deficiency, or classic galactosemia, is life-threatening in the newborn period. The treatment for classic galactosemia is dietary restriction of lactose. Although implementation of lactose restricted diet is efficient in resolving the acute complications, it is not sufficient to prevent long-term complications affecting the brain and female gonads, the two main target organs of damage. Implementation of molecular genetics diagnostic tools and GALT enzyme assays are instrumental in distinguishing classic galactosemia from clinical and biochemical variant forms of GALT deficiency. Better understanding of mechanisms responsible for the phenotypic variation even within the same genotype is essential to provide appropriate counseling for families. Utilization of a lactose restricted diet is also recommended for GALK deficiency and some rare forms of GALE deficiency. Novel modes of therapies are being explored; they may be beneficial if access issues to the affected tissues are circumvented and optimum use of therapeutic window is achieved.
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Affiliation(s)
- Didem Demirbas
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Ana I Coelho
- Department of Pediatrics, Department of Clinical Genetics, GROW-School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - M Estela Rubio-Gozalbo
- Department of Pediatrics, Department of Clinical Genetics, GROW-School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Gerard T Berry
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
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6
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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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7
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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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8
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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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9
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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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10
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Singh R, Thapa BR, Kaur G, Prasad R. Biochemical and molecular characterization of GALT gene from Indian galactosemia patients: Identification of 10 novel mutations and their structural and functional implications. Clin Chim Acta 2012; 414:191-6. [DOI: 10.1016/j.cca.2012.09.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2012] [Accepted: 09/09/2012] [Indexed: 11/28/2022]
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11
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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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12
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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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13
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Milánkovics I, Schuler Á, Kámory E, Csókay B, Fodor F, Somogyi C, Németh K, Fekete G. Molecular and clinical analysis of patients with classic and Duarte galactosemia in western Hungary. Wien Klin Wochenschr 2010; 122:95-102. [DOI: 10.1007/s00508-010-1311-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Accepted: 12/21/2009] [Indexed: 11/29/2022]
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Milánkovics I, Schuler Á, Németh K, Somogyi C, Fekete G. Frequencies of the Los Angeles and Duarte galactose-1-phosphate uridyltransferase variant alleles in the Hungarian population. Orv Hetil 2009; 150:1301-5. [DOI: 10.1556/oh.2009.28671] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
A klasszikus galactosaemia autoszomális recesszív módon öröklődő anyagcsere-betegség, amelynek hátterében a galaktóz-1-foszfát-uridil-transzferáz (GALT) enzim defektusa áll. Hazánkban a betegséget az újszülöttkori tömegszűrés keretében, 1976 óta szűrik. A p.N314D mutáció asszociál a GALT enzim Los Angeles és a Duarte variánsaival, attól függően, hogy a mutáció mely polimorfizmusokkal öröklődik együtt
cis
helyzetben.
Célkitűzés:
Munkánk célja volt a magyar egészséges populációban a p.N314D mutáció, valamint a Los Angeles és Duarte variánsok gyakoriságát meghatározni.
Módszerek:
A 100 donor személyből izolált genomiális DNS-mintát polimeráz láncreakció során amplifikáltuk, majd restrikciós endonukleázzal emésztettük.
Eredmények:
A p.N314D mutáció, a Los Angeles variáns és a Duarte variáns allélgyakorisága az általunk vizsgált populációban 11,5%, 2,5%, illetve 9% volt.
Következtetés:
A magyar populációban a Los Angeles és Duarte varánsok allélgyakorisága jól korrelál más kaukázusi populációkban detektált gyakoriságokkal.
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Affiliation(s)
- Ilona Milánkovics
- 1 Semmelweis Egyetem, Általános Orvostudományi Kar II. Gyermekgyógyászati Klinika Budapest Tűzoltó u. 7–9. 1094
| | | | - Krisztina Németh
- 1 Semmelweis Egyetem, Általános Orvostudományi Kar II. Gyermekgyógyászati Klinika Budapest Tűzoltó u. 7–9. 1094
| | | | - György Fekete
- 1 Semmelweis Egyetem, Általános Orvostudományi Kar II. Gyermekgyógyászati Klinika Budapest Tűzoltó u. 7–9. 1094
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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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16
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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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17
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Karas-Kuzelicki N, Pfeifer V, Lukac-Bajalo J. Synergistic effect of high lactase activity genotype and galactose-1-phosphate uridyl transferase (GALT) mutations on idiopathic presenile cataract formation. Clin Biochem 2008; 41:869-74. [PMID: 18454942 DOI: 10.1016/j.clinbiochem.2008.04.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Revised: 02/05/2008] [Accepted: 04/03/2008] [Indexed: 10/22/2022]
Abstract
OBJECTIVES To evaluate the possible synergistic role of partial galactose metabolism defects, high lactase (LPH) genotype and lactose and galactose ingestion in presenile cataract formation. DESIGN AND METHODS 51 patients with idiopathic presenile cataracts and 172 healthy cataract-free subjects were genotyped to determine their galactose-1-phosphate uridyl transferase (GALT) and LPH status. Whole milk, skimmed milk and yoghurt consumption was recorded in 19 cataract patients and 172 controls by questionnaire. RESULTS GALT mutations and whole milk consumption increased the risk of cataract formation in high LPH genotype group, but not in lactose intolerant subjects. Logistic regression analysis showed the synergistic effect of GALT and LPH mutations on cataract formation. CONCLUSIONS High lactase activity genotypes and mutations in galactose-1-phosphate uridyl transferase have a synergistic effect on presenile cataract formation.
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18
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Christensen M, Duno M, Lund AM, Skovby F, Christensen E. Xanthurenic aciduria due to a mutation in KYNU encoding kynureninase. J Inherit Metab Dis 2007; 30:248-55. [PMID: 17334708 DOI: 10.1007/s10545-007-0396-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2006] [Revised: 01/11/2007] [Accepted: 01/29/2007] [Indexed: 11/27/2022]
Abstract
Massive urinary excretion of xanthurenic acid, 3-hydroxykynurenine and kynurenine, known as xanthurenic aciduria or hydroxykynureninuria, in a young Somali boy suggested kynureninase deficiency. Mutation analysis of KYNU encoding kynureninase of the index case revealed homozygosity for a c.593 A > G substitution leading to a threonine-to-alanine (T198A) shift. A younger brother was found to have a similar excretion pattern and the same genotype. At present, neither of the two boys has symptoms of niacin deficiency. This is the first report linking xanthurenic aciduria to a mutation in the gene encoding kynureninase.
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Affiliation(s)
- M Christensen
- Department of Clinical Genetics, Rigshospitalet 4062, Blegdamsvej 9, DK-2100, Copenhagen, Denmark.
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19
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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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20
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Flanagan JM, Tighe O, O' Neill C, Naughten E, Mayne PD, Croke DT. Identification of sequence variation in the galactose-1-phosphate uridyl transferase gene by dHPLC. Mol Genet Metab 2004; 81:133-6. [PMID: 14741195 DOI: 10.1016/j.ymgme.2003.10.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Transferase-deficient galactosaemia is an inherited disorder of carbohydrate metabolism, caused by mutation at the galactose-1-phosphate uridyl transferase (GALT) locus. A denaturing high performance liquid chromatography (dHPLC) method was developed for variant scanning of the GALT gene. The method unequivocally identified the Duarte D1, D2, Q188R, and K285N GALT alleles and associated polymorphisms. Length polymorphism in an intronic Alu repeat was characterised and a novel Single Nucleotide Polymorphism (IVS10nt-322g-->t) associated with the D1 allele was identified.
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Affiliation(s)
- Jonathon M Flanagan
- Department of Pathology, The Children's University Hospital, Temple Street, Dublin 1, Ireland
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21
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Karas N, Gobec L, Pfeifer V, Mlinar B, Battelino T, Lukac-Bajalo J. Mutations in galactose-1-phosphate uridyltransferase gene in patients with idiopathic presenile cataract. J Inherit Metab Dis 2003; 26:699-704. [PMID: 14707519 DOI: 10.1023/b:boli.0000005660.88944.2f] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Impaired activity of the enzyme galactose-1-phosphate uridyltransferase (GALT) has been proposed as a risk factor for idiopathic presenile cataract. A study was undertaken to determine the prevalence of the three most common mutations in the GALT gene (Q188R, K285N and N314D, including its variant Duarte-2) in a group of Slovenian patients with idiopathic presenile cataract. GALT activity was determined in the erythrocytes of 30 cataract patients. DNA was isolated from their blood and analysed for Q188R, K285N and N314D mutations and IVS5-24G>A intronic variation by means of polymerase chain reaction and digestion with restriction enzymes. The average GALT activity of the cataract group was 19.5+/-4.9 U/g Hb, which is lower than the normal range (p = 0.034). Frequencies of Q188R, K285N, N314D and Duarte-2 alleles in the cataract group were 0.00%, 5.0%, 11.7% and 3.3%, respectively. Only the frequency of the K285N mutation was significantly higher in the patient group than in the control group (p = 0.0244). Our results support the reported association of decreased GALT activity with idiopathic presenile cataract. Molecular analysis indicates that, in the Slovenian population, this association is linked to the K285N mutation, which is neonatally benign in heterozygotes.
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Affiliation(s)
- N Karas
- Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
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22
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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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23
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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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24
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Elsas LJ, Lai K, Saunders CJ, Langley SD. Functional analysis of the human galactose-1-phosphate uridyltransferase promoter in Duarte and LA variant galactosemia. Mol Genet Metab 2001; 72:297-305. [PMID: 11286503 DOI: 10.1006/mgme.2001.3157] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Human galactose-1-phosphate uridyltransferase (hGALT) is an evolutionarily conserved enzyme central to D-galactose metabolism. The impairment of hGALT causes galactosemia. One missense mutation, an aspartate to asparagine substitution at amino acid 314 (N314D), impairs 50% activity in the homozygous state in some patients but gives near normal activity in others. The former condition is called Duarte (D) and the latter, Los Angeles (LA). The D allele is linked to hGALT polymorphisms including a deletion 5'to the translation start site (-119 to -116delGTCA), g1391G --> A and g1105G --> C. The LA allele is linked to a g1721C --> T transition. To investigate possible mechanisms for differences in hGALT activity between the D and LA alleles, we sequenced 3951 nucleotides of genomic DNA 5' to the hGALT translation start site. Using a dual-luciferase reporter system to express deletion constructs of the hGALT promoter, we noted both positive and negative regulatory regions. Two putative positive regulatory domains overlap with the naturally occurring -119 to -116delGTCA linked to Duarte. One is an E-box motif (CACGTG) at -117 to -112 bp. The second is an AP-1 motif (TCAGTCAG) at -124 to -119 bp. The delGTCA mutation confers reduced luciferase activity to transfected cell lines derived from human ovarian and liver neoplasms. Additionally, human lymphoblasts derived from patients with the Duarte allele have reduced GALT mRNA. We conclude that the human GALT gene is regulated in the first -165 bp of its promoter region by positive regulators of GALT gene expression. The -119 to -116delGTCA reduces hGALT transcription resulting in reduced GALT activity in the Duarte allele.
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Affiliation(s)
- L J Elsas
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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25
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Tyfield L, Reichardt J, Fridovich-Keil J, Croke DT, Elsas LJ, Strobl W, Kozak L, Coskun T, Novelli G, Okano Y, Zekanowski C, Shin Y, Boleda MD. Classical galactosemia and mutations at the galactose-1-phosphate uridyl transferase (GALT) gene. Hum Mutat 2000; 13:417-30. [PMID: 10408771 DOI: 10.1002/(sici)1098-1004(1999)13:6<417::aid-humu1>3.0.co;2-0] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Classical galactosemia is caused by a deficiency in activity of the enzyme galactose-1-phosphate uridyl transferase (GALT), which, in turn, is caused by mutations at the GALT gene. The disorder exhibits considerable allelic heterogeneity and, at the end of 1998, more than 150 different base changes were recorded in 24 different populations and ethnic groups in 15 countries worldwide. The mutations most frequently cited are Q188R, K285N, S135L, and N314D. Q188R is the most common mutation in European populations or in those predominantly of European descent. Overall, it accounts for 60-70% of mutant chromosomes, but there are significant differences in its relative frequency in individual populations. Individuals homoallelic for Q188R tend to have a severe phenotype and this is in keeping with the virtually complete loss of enzyme activity observed in in vitro expression systems. Globally, K285N is rarer, but in many European populations it can be found on 25-40% of mutant chromosomes. It is invariably associated with a severe phenotype. S135L is found almost exclusively in African Americans. In vitro expression results are discrepant, but some individuals carrying S135L appear to exhibit GALT activity in some tissues. Duarte 1 (or Los Angeles) and Duarte 2 (or Duarte) variants carry the same amino acid substitution, N314D, even though D1 is associated with increased erythrocyte GALT activity and D2 with reduced activity. N314D is in linkage disequilibrium with other base changes that differ on the D1 and D2 alleles. N314D does not impair GALT activity in in vitro expression systems. However, there are differences in the abundance of GALT protein in lymphoblastoid cells lines from D2 and D1 individuals. It is unclear whether the specific molecular changes that distinguish the D1 and D2 alleles account for the different activities. The considerable genetic heterogeneity documented to date undoubtedly contributes to the phenotypic heterogeneity that is observed in galactosemia. The additional effects of nonallelic variation and other constitutional factors on phenotypic variability remain to be elucidated.
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Affiliation(s)
- L Tyfield
- The Lewis Laboratories, Southmead Hospital, Bristol, England, United Kingdom.
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26
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Zekanowski C, Radomyska B, Bal J. Molecular characterization of Polish patients with classical galactosaemia. J Inherit Metab Dis 1999; 22:679-82. [PMID: 10399107 DOI: 10.1023/a:1005511020607] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- C Zekanowski
- Department of Genetics, National Research Institute of Mother and Child, Warsaw, Poland
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27
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Shin YS, Zschocke J, Das AM, Podskarbi T. Molecular and biochemical basis for variants and deficiency forms of galactose-1-phosphate uridyltransferase. J Inherit Metab Dis 1999; 22:327-9. [PMID: 10384398 DOI: 10.1023/a:1005516523196] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Y S Shin
- University Children's Hospital of Munich, Germany.
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28
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Shin YS, Koch HG, Köhler M, Hoffmann G, Patsoura A, Podskarbi T. Duarte-1 (Los Angeles) and Duarte-2 (Duarte) variants in Germany: two new mutations in the GALT gene which cause a GALT activity decrease by 40-50% of normal in red cells. J Inherit Metab Dis 1998; 21:232-5. [PMID: 9686364 DOI: 10.1023/a:1005303818858] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Y S Shin
- University Children's Hospital, Munich, Germany
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29
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Wells L, Fridovich-Keil JL. Biochemical characterization of the S135L allele of galactose-1-phosphate uridylyltransferase associated with galactosaemia. J Inherit Metab Dis 1997; 20:633-42. [PMID: 9323558 DOI: 10.1023/a:1005314207513] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Impairment of the human enzyme galactose-1-phosphate uridylyltransferase (GALT) results in the potentially lethal disorder galactosaemia. The S135L mutation, which accounts for almost 50% of the GALT alleles in galactosaemia patients of African-American descent, has been associated with activities ranging from null to wild-type by different investigators examining cell lysates representing different tissues or model systems. Because of the crude nature of the lysates examined, however, and the absence of quantitative measures concerning GALT abundance in most of those lysates, the available data do not distinguish between differences in GALT enzyme expression/abundance, specific activity, or kinetic constants in these different tissues or systems. In an effort to overcome this uncertainty and investigate the biochemical impact of the S135L substitution on human GALT function under defined conditions, we have overexpressed both wild-type and S135L-mutant GALT sequences in a null-background yeast expression system, and purified both proteins to near homogeneity. Abundance of the wild-type and mutant proteins in crude yeast lysates differed by approximately 2-fold. Kinetic studies of the purified proteins, however, demonstrated that although K(m) values differed by < 2-fold, specific activities differed by 10-fold. Temperature-activity profiles revealed no significant differences, and coprecipitation studies demonstrated that S135L-hGALT subunits remained competent to self-associate in vivo. We conclude that the S135L substitution causes either steric or electrochemical changes sufficiently close to the active site in human GALT to result in partial impairment of the transferase reaction.
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Affiliation(s)
- L Wells
- Graduate Program in Biochemistry and Molecular Biology, Emory University School of Medicine, Atlanta, Georgia, USA
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