Franciele Cabral Pinheiro1, Fernanda Sperb-Ludwig2, Rodrigo Ligabue-Braun3, Lavínia Schüler-Faccini4, Carolina Fischinger Moura de Souza5, Filippo Vairo6, Ida Vanessa Doederlein Schwartz7. 1. Post Graduate Program in Genetics and Molecular Biology, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil; BRAIN Laboratory, Center for Experimental Research (CPE), Hospital de Clínicas de Porto Alegre (HCPA), Porto Alegre, RS, Brazil; Universidade Federal do Pampa (UNIPAMPA), Itaqui, RS, Brazil. 2. Post Graduate Program in Genetics and Molecular Biology, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil; BRAIN Laboratory, Center for Experimental Research (CPE), Hospital de Clínicas de Porto Alegre (HCPA), Porto Alegre, RS, Brazil. Electronic address: fsperb@hcpa.edu.br. 3. Post Graduate Program in Cell and Molecular Biology, Center of Biotechnology, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil; Department of Pharmaceutical Sciences, Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, RS, Brazil. 4. INAGEMP-Instituto Nacional de Genética Médica Populacional, Porto Alegre, RS, Brazil; Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; Medical Genetics Service, HCPA, Porto Alegre, RS, Brazil. 5. Medical Genetics Service, HCPA, Porto Alegre, RS, Brazil. 6. Center for Individualized Medicine, Mayo Clinic, Rochester, MN, USA; Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA. 7. Post Graduate Program in Genetics and Molecular Biology, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil; BRAIN Laboratory, Center for Experimental Research (CPE), Hospital de Clínicas de Porto Alegre (HCPA), Porto Alegre, RS, Brazil; Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; Medical Genetics Service, HCPA, Porto Alegre, RS, Brazil.
Abstract
INTRODUCTION: Fructose-1,6-bisphosphatase deficiency (FBPase deficiency) is a rare inborn error of metabolism that affects gluconeogenesis. Ketotic hypoglycemia is the main symptom and can occur at any age, usually after long periods of fasting or during illness. The diagnosis may be achieved by measurement of the enzyme activity in a liver sample, but FBP1 analysis has become the most common approach. AIM: To characterize the genotype of Southern Brazilian FBPase-deficient patients. METHODOLOGY: The FBP1 gene of six unrelated patients (one had consanguineous parents) with previous diagnoses of FBPase deficiency (enzymatic, pts A, B, D, E; genetic through Next-Generation Sequencing-NGS, pt F; enzymatic and Sanger sequencing, pt C) was first analyzed through NGS. Pathogenic variants found in NGS were confirmed by Sanger sequencing. The pathogenicity of novel missense variants was evaluated through in silico analysis. RESULTS: Five patients (pt A, B, D, E, F) had their genotype identified by NGS, all of them being homozygous. In Pt C, NGS detected only one pathogenic variant. Among the 11 alleles analyzed, only three variants were found, two being novel: c.958G > A and c.986T > C. In silico analysis indicated the pathogenicity of both variants. Interestingly, the three variants seem to be linked to specific haplotypes, indicating that an endogamy effect may be acting on these alleles in the population of Southern Brazil. CONCLUSIONS: Our data suggest that NGS is a good tool for the diagnosis of FBPase deficiency. Variants c.958G > A and c.986T > C are the most prevalent variants in the country.
INTRODUCTION:Fructose-1,6-bisphosphatase deficiency (FBPase deficiency) is a rare inborn error of metabolism that affects gluconeogenesis. Ketotic hypoglycemia is the main symptom and can occur at any age, usually after long periods of fasting or during illness. The diagnosis may be achieved by measurement of the enzyme activity in a liver sample, but FBP1 analysis has become the most common approach. AIM: To characterize the genotype of Southern Brazilian FBPase-deficient patients. METHODOLOGY: The FBP1 gene of six unrelated patients (one had consanguineous parents) with previous diagnoses of FBPase deficiency (enzymatic, pts A, B, D, E; genetic through Next-Generation Sequencing-NGS, pt F; enzymatic and Sanger sequencing, pt C) was first analyzed through NGS. Pathogenic variants found in NGS were confirmed by Sanger sequencing. The pathogenicity of novel missense variants was evaluated through in silico analysis. RESULTS: Five patients (pt A, B, D, E, F) had their genotype identified by NGS, all of them being homozygous. In Pt C, NGS detected only one pathogenic variant. Among the 11 alleles analyzed, only three variants were found, two being novel: c.958G > A and c.986T > C. In silico analysis indicated the pathogenicity of both variants. Interestingly, the three variants seem to be linked to specific haplotypes, indicating that an endogamy effect may be acting on these alleles in the population of Southern Brazil. CONCLUSIONS: Our data suggest that NGS is a good tool for the diagnosis of FBPase deficiency. Variants c.958G > A and c.986T > C are the most prevalent variants in the country.