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Stettner NM, Cutler DJ, Fridovich-Keil JL. Racial and ethnic diversity of classic and clinical variant galactosemia in the United States. Mol Genet Metab 2023; 138:107542. [PMID: 36848716 PMCID: PMC10133179 DOI: 10.1016/j.ymgme.2023.107542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 02/14/2023] [Accepted: 02/16/2023] [Indexed: 02/25/2023]
Abstract
Classic and clinical variant galactosemia (CG/CVG) are allelic, autosomal recessive disorders that result from deficiency of galactose-1-P uridylyltransferase (GALT). CG/CVG has been reported globally among patients of diverse ancestries, but most large studies of outcomes have included, almost exclusively, patients categorized as White or Caucasian. As a first step to explore whether the cohorts studied are representative of the CG/CVG population at large, we sought to define the racial and ethnic makeup of CG/CVG newborns in a diverse population with essentially universal newborn screening (NBS) for galactosemia: the United States (US). First, we estimated the predicted racial and ethnic distribution of CG/CVG by combining the reported demographics of US newborns from 2016 to 2018 with predicted homozygosity or compound heterozygosity of pathogenic, or likely pathogenic, GALT alleles from the relevant ancestral groups. Incorporating some simplifying assumptions, we predicted that of US newborns diagnosed with CG/CVG, 65% should be White (non-Hispanic), 23% should be Black (non-Hispanic), 10% should be Hispanic, and 2% should be Asian (non-Hispanic). Next, we calculated the observed racial and ethnic distribution of US newborns diagnosed with CG/CVG using available de-identified data from state NBS programs from 2016 to 2018. Of the 235 newborns in this cohort, 41 were categorized as other or unknown. Of the remaining 194, 66% were White (non-Hispanic or ethnicity unknown), 16% were Black (non-Hispanic or ethnicity unknown),15% were Hispanic, and 2% were Asian (non-Hispanic or ethnicity unknown). This observed distribution was statistically indistinguishable from the predicted distribution. To the limits of our study, these data confirm the racial and ethnic diversity of newborns with CG/CVG in the US, demonstrate an approach for estimating CG/CVG racial and ethnic diversity in other populations, and raise the troubling possibility that current understanding of long-term outcomes in CG/CVG may be skewed by ascertainment bias of the cohorts studied.
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Affiliation(s)
| | - David J Cutler
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA
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Katler Q, Stepien KM, Paull N, Patel S, Adams M, Balci MC, Berry GT, Bosch AM, De La O A, Demirbas D, Edman J, Ficicioglu C, Goff M, Hacker S, Knerr I, Lancaster K, Li H, Mendelsohn BA, Nichols B, de Rezende Pinto WBV, Rocha JC, Rubio-Gozalbo ME, Saad-Naguib M, Scholl-Buergi S, Searcy S, de Souza PVS, Wittenauer A, Fridovich-Keil JL. A multinational study of acute and long-term outcomes of Type 1 galactosemia patients who carry the S135L (c.404C > T) variant of GALT. J Inherit Metab Dis 2022; 45:1106-1117. [PMID: 36093991 PMCID: PMC9643640 DOI: 10.1002/jimd.12556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 08/23/2022] [Accepted: 09/09/2022] [Indexed: 11/08/2022]
Abstract
Patients with galactosemia who carry the S135L (c.404C > T) variant of galactose-1-P uridylyltransferase (GALT), documented to encode low-level residual GALT activity, have been under-represented in most prior studies of outcomes in Type 1 galactosemia. What is known about the acute and long-term outcomes of these patients, therefore, is based on very limited data. Here, we present a study comparing acute and long-term outcomes of 12 patients homozygous for S135L, 25 patients compound heterozygous for S135L, and 105 patients homozygous for two GALT-null (G) alleles. This is the largest cohort of S135L patients characterized to date. Acute disease following milk exposure in the newborn period was common among patients in all 3 comparison groups in our study, as were long-term complications in the domains of speech, cognition, and motor outcomes. In contrast, while at least 80% of both GALT-null and S135L compound heterozygous girls and women showed evidence of an adverse ovarian outcome, prevalence was only 25% among S135L homozygotes. Further, all young women in this study with even one copy of S135L achieved spontaneous menarche; this is true for only about 33% of women with classic galactosemia. Overall, we observed that while most long-term outcomes trended milder among groups of patients with even one copy of S135L, many individual patients, either homozygous or compound heterozygous for S135L, nonetheless experienced long-term outcomes that were not mild. This was true despite detection by newborn screening and both early and life-long dietary restriction of galactose. This information should empower more evidence-based counseling for galactosemia patients with S135L.
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Affiliation(s)
- Quinton Katler
- Division of Reproductive Endocrinology and Infertility, Department of Gynecology and Obstetrics, Emory University School of Medicine, Atlanta, Georgia USA
| | - Karolina M. Stepien
- Adult Inherited Metabolic Diseases Department, Salford Royal Foundation NHS Trust, Salford, Greater Manchester, UK
| | - Nathan Paull
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia USA
| | - Sneh Patel
- Emory College, Emory University, Atlanta, Georgia USA
| | - Michael Adams
- UNC School of Medicine, Division of Pediatric Genetics and Metabolism, Chapel Hill, North Carolina USA
| | - Mehmet Cihan Balci
- Department of Pediatric Metabolic Disease, Istanbul Medical School, Fatihİstanbul, Turkey
| | - Gerard T. Berry
- Division of Genetics and Genomics, Department of Pediatrics, The Manton Center for Orphan Disease Research, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts USA
| | - Annet M. Bosch
- Amsterdam UMC location University of Amsterdam, Emma Children’s Hospital, Department of Pediatrics, Division of Metabolic Diseases, Amsterdam Gastroenterology Endocrinology Metabolism, Meibergdreef 9, Amsterdam, the Netherlands
| | | | - Didem Demirbas
- Division of Genetics and Genomics, Department of Pediatrics, The Manton Center for Orphan Disease Research, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts USA
| | - Julianna Edman
- Department of Pediatric Genetics, University of Illinois-Chicago, Chicago, Illinois USA
| | - Can Ficicioglu
- The Children’s Hospital of Philadelphia, Division of Human Genetics and Metabolism, Perelman School of Medicine at The University of Pennsylvania, Philadelphia, Pennsylvania USA
| | - Melanie Goff
- Division of Genetic and Genomic Medicine, Nationwide Children’s Hospital, Columbus, Ohio USA
| | - Stephanie Hacker
- Department of Human Genetics, University of Miami Miller School of Medicine, Miami, Florida USA
| | - Ina Knerr
- National Centre for Inherited Metabolic Disorders, Temple St. Children’s University Hospital, Dublin, Ireland
| | - Kristen Lancaster
- UNC School of Medicine, Division of Pediatric Genetics and Metabolism, Chapel Hill, North Carolina USA
| | - Hong Li
- Departments of Human Genetics and Pediatrics, Emory University School of Medicine, Atlanta, Georgia USA
| | - Bryce A. Mendelsohn
- Department of Genetics, Oakland Medical Center, Kaiser Permanente, Oakland, California USA
| | - Brandi Nichols
- Department of Clinical Nutrition, Arkansas Children’s Hospital, Little Rock, Arkansas USA
| | | | - Júlio César Rocha
- Nutrition & Metabolism, NOVA Medical School, Faculdade de Ciências Médicas, Universidade Nova de Lisboa Reference Centre of Inherited Metabolic Diseases, Centro Hospitalar Universitário de Lisboa Central, and Center for Health Technology and Services Research (CINTESIS), NOVA Medical School, Lisboa, Portugal
| | - M Estela Rubio-Gozalbo
- Department of Pediatrics, Department of Clinical Genetics, GROW-School for Oncology and Reproduction, European Reference Network for Hereditary Metabolic Disorders (MetabERN) member and United for Metabolic Diseases member, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Michael Saad-Naguib
- Department of Human Genetics, University of Miami Miller School of Medicine, Miami, Florida USA
| | | | - Sarah Searcy
- Division of Genetic and Genomic Medicine, Nationwide Children’s Hospital, Columbus, Ohio USA
| | | | - Angela Wittenauer
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia USA
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Crespo C, Eiroa H, Otegui MI, Bonetto MC, Chertkoff L, Gravina LP. Molecular analysis of GALT gene in Argentinian population: Correlation with enzyme activity and characterization of a novel Duarte-like allele. Mol Genet Metab Rep 2020; 25:100695. [PMID: 33335841 PMCID: PMC7733017 DOI: 10.1016/j.ymgmr.2020.100695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 11/29/2020] [Accepted: 12/01/2020] [Indexed: 11/02/2022] Open
Abstract
Background Classical galactosemia is an autosomal recessive inherited metabolic disorder caused by mutations in the galactose-1-phosphate uridyltransferase (GALT) gene. GALT enzyme deficiency leads to the accumulation of galactose-1-phosphate in various organs, causing hepatic, renal and cerebral impairment. Over 300 mutations have been reported in the GALT gene. The aim of this study was to describe molecular characterization of GALT gene in Argentinian patients with decreased GALT activity, and to correlate molecular results with enzyme activity. Methods 37 patients with enzyme activity below 6.3 μmol/h/g Hb (35% of normal value) were included. GALT activity was measured on red blood cells. DNA was extracted from peripheral blood. p.Gln188Arg mutation was studied by PCR-RFLP and, on samples negative or heterozygous, GALT gene was sequenced. In vivo splicing analysis of the GALT gene was performed on RNA extracted from leukocytes of one patient. Results 14 different sequence variations were identified among 72 unrelated alleles. The two most common disease-causing mutations were p.Gln188Arg (24/72) and p.Lys285Asn (9/72). Three novel mutations were detected. One of them, c.688G>A, caused partial skipping of exon 9 of the GALT gene. Enzyme activity correlated with GALT genotype in 36 of the 37 patients. Conclusion This is the first report of sequence variations in the GALT gene in the Argentinian population. This study highlights the contribution of the molecular analysis to the diagnosis of Galactosemia and reveals c.688G>A as a novel Duarte-like variant, with a high prevalence in our population.
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Affiliation(s)
- Carolina Crespo
- Laboratorio de Biología Molecular, Servicio de Genética, Hospital de Pediatría "Prof. Dr. Juan P. Garrahan", Buenos Aires, Argentina
| | - Hernán Eiroa
- Servicio de Errores Congénitos del Metabolismo, Hospital de Pediatría "Prof. Dr. Juan P. Garrahan", Buenos Aires, Argentina
| | - María Inés Otegui
- Laboratorio de Errores Congénitos del Metabolismo, Hospital de Pediatría "Prof. Dr. Juan P. Garrahan", Buenos Aires, Argentina
| | - Mara Cecilia Bonetto
- Laboratorio de Biología Molecular, Servicio de Genética, Hospital de Pediatría "Prof. Dr. Juan P. Garrahan", Buenos Aires, Argentina
| | - Lilien Chertkoff
- Área de Laboratorios de Especialidades, Hospital de Pediatría "Prof. Dr. Juan P. Garrahan", Buenos Aires, Argentina
| | - Luis Pablo Gravina
- Laboratorio de Biología Molecular, Servicio de Genética, Hospital de Pediatría "Prof. Dr. Juan P. Garrahan", Buenos Aires, Argentina
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Kotb MA, Mansour L, William Shaker Basanti C, El Garf W, Ali GIZ, Mostafa El Sorogy ST, Kamel IEM, Kamal NM. Pilot study of classic galactosemia: Neurodevelopmental impact and other complications urge neonatal screening in Egypt. J Adv Res 2018; 12:39-45. [PMID: 30038819 PMCID: PMC6054589 DOI: 10.1016/j.jare.2018.02.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 01/25/2018] [Accepted: 02/02/2018] [Indexed: 12/26/2022] Open
Abstract
Classic galactosemia is caused by deficiency of galactose-1-phosphate uridylyltransferase (GALT). It causes serious morbidity and mortality if left untreated. Screening for galactosemia is not included in Egyptian neonatal screening program. The study aimed to define clinical presentation and complications of galactosemia at Pediatric Hepatology Clinic, Cairo University, Egypt. Thus, the clinical presentation, course and outcome of 37 children with documented galactosemia was studied. Jaundice was the main presentation (67.6%). Other presentations included; convulsions (29.7%), motor retardation (24.3%), mental retardation (5.4%), microcephaly (5.4%), failure to thrive (16.2%), hepatomegaly (62.2%), splenomegaly (35.1%), vomiting (16.2%), diarrhea (8.1%), liver cell failure (10.8%), renal tubular acidosis (5.4%), cataract (5.4%), autoimmune hepatitis (2.7%), self-mutilation (2.7%), combined immune deficiency (2.7%) and kernicterus (2.7%). There was no correlation of residual enzyme activity to severity, clinical presentation, liver function tests, liver biopsy findings or outcome apart from highly significant correlation with repeated chest infections (P = 0.001). Duration to diagnosis and exposure to galactose in diet correlated with liver pathology severity i.e. hepatocyte necrosis (P = 0.003) and cytoskeleton damage (P = 0.003), but not to outcome. Galactosemia should be suspected in any child with liver, neurologic disease and/or immunodeficiency. Its complications are potentially preventable. Early detection is mandatory to prevent serious morbidity and mortality. Initiation of neonatal screening for galactosemia in Egypt is recommended.
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Affiliation(s)
- Magd A Kotb
- Department of Pediatrics, Pediatric Hepatology Unit, Faculty of Medicine, Cairo University, Egypt
| | - Lobna Mansour
- Department of Pediatrics, Pediatric Neurology Unit, Faculty of Medicine, Cairo University, Egypt
| | | | - Wael El Garf
- Pediatric Medicine Department, National Research Center, Cairo, Egypt
| | - Ghada I Z Ali
- Department of Pediatrics, Maady Military Hospital, Cairo, Egypt
| | | | - Inas E M Kamel
- Pediatric Medicine Department, National Research Center, Cairo, Egypt
| | - Naglaa M Kamal
- Department of Pediatrics, Pediatric Hepatology Unit, Faculty of Medicine, Cairo University, Egypt
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Ramadža DP, Sarnavka V, Vuković J, Fumić K, Krželj V, Lozić B, Pušeljić S, Pereira H, Silva MJ, Tavares de Almeida I, Barić I, Rivera I. Molecular basis and clinical presentation of classic galactosemia in a Croatian population. J Pediatr Endocrinol Metab 2018; 31:71-75. [PMID: 29252199 DOI: 10.1515/jpem-2017-0302] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 11/02/2017] [Indexed: 11/15/2022]
Abstract
BACKGROUND Classic galactosemia is an autosomal recessive disorder of galactose metabolism caused by severely decreased activity of galactose-1-phosphate uridylyltransferase (GALT) due to pathogenic mutations in the GALT gene. To date more than 330 mutations have been described, with p.Q188R and p.K285N being the most common in Caucasian populations. Although acute manifestations can be fully avoided by a galactose-restricted diet, chronic complications, such as neurological ones, cannot be prevented in a significant number of patients despite compliance with the dietary treatment. METHODS A cohort of 16 galactosemic Croatian patients, including one pair of siblings, was studied. Molecular characterization was performed by direct sequence analysis of the GALT gene. RESULTS Sixteen patients were analyzed and only four different mutations were detected. As expected, p.Q188R and p.K285N were common, accounting for 40% and 37% of unrelated alleles, respectively. The third mutation accounting for 20% of mutant alleles was p.R123X causing a premature stop codon, is thus considered to be severe, which is in accordance with the phenotype presented by the homozygous patient described here. The fourth mutation p.E271D was found in a single allele. More than half of our patients manifested some chronic neurological complications. CONCLUSIONS This is the first report on mutational and phenotypic spectra of classic galactosemia in Croatia that expands the knowledge on the mutational map of the GALT gene across Europe and reveals the genetic homogeneity of the Croatian population.
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Affiliation(s)
- Danijela Petković Ramadža
- Department of Pediatrics, University Hospital Centre, Zagreb, Croatia.,School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Vladimir Sarnavka
- Department of Pediatrics, University Hospital Centre, Zagreb, Croatia
| | - Jurica Vuković
- Department of Pediatrics, University Hospital Centre, Zagreb, Croatia.,School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Ksenija Fumić
- Department of Laboratory Diagnostics, University Hospital Centre, Zagreb, Croatia
| | - Vjekoslav Krželj
- Department of Pediatrics, University Hospital Centre, Split, Croatia
| | - Bernarda Lozić
- Department of Pediatrics, University Hospital Centre, Split, Croatia
| | - Silvija Pušeljić
- Department of Pediatrics, University Hospital Centre, Osijek, Croatia
| | - Hana Pereira
- Metabolism and Genetics Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal
| | - Maria João Silva
- Metabolism and Genetics Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal.,Department of Biochemistry and Human Biology, Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal
| | - Isabel Tavares de Almeida
- Metabolism and Genetics Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal
| | - Ivo Barić
- Department of Pediatrics, University Hospital Centre, Zagreb, Croatia.,School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Isabel Rivera
- Metabolism and Genetics Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal.,Department of Biochemistry and Human Biology, Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal
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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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Narravula A, Garber KB, Askree SH, Hegde M, Hall PL. Variants of uncertain significance in newborn screening disorders: implications for large-scale genomic sequencing. Genet Med 2017; 19:77-82. [DOI: 10.1038/gim.2016.67] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 04/11/2016] [Indexed: 12/24/2022] Open
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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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 06/24/2014] [Indexed: 01/19/2023]
Abstract
Knowledge of the impact of variations on protein structure can enhance the comprehension of the mechanisms of genetic diseases related to that protein. Here, we present a new version of GALT Protein Database, a Web-accessible data repository for the storage and interrogation of structural effects of variations of the enzyme galactose-1-phosphate uridylyltransferase (GALT), the impairment of which leads to classic Galactosemia, a rare genetic disease. This new version of this database now contains the models of 201 missense variants of GALT enzyme, including heterozygous variants, and it allows users not only to retrieve information about the missense variations affecting this protein, but also to investigate their impact on substrate binding, intersubunit interactions, stability, and other structural features. In addition, it allows the interactive visualization of the models of variants collected into the database. We have developed additional tools to improve the use of the database by nonspecialized users. This Web-accessible database (http://bioinformatica.isa.cnr.it/GALT/GALT2.0) represents a model of tools potentially suitable for application to other proteins that are involved in human pathologies and that are subjected to genetic variations.
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Coelho AI, Lourenço S, Trabuco M, Silva MJ, Oliveira A, Gaspar A, Diogo L, Tavares de Almeida I, Vicente JB, Rivera I. Functional correction by antisense therapy of a splicing mutation in the GALT gene. Eur J Hum Genet 2015; 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] [What about the content of this article? (0)] [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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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] [What about the content of this article? (0)] [Affiliation(s)] [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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