Estudo genético de pacientes brasileiros com miopatias relacionadas à selenoproteína N1

Abstract

Introduction: Different kinds of myopathy are related to the selenoprotein N1 gene, among which: congenital muscular dystrophy with rigid spine (RSMD) multiminicore myopathy (Mm), desminopathy with Mallory body and congenital fiber-type disproportion myopathy (CFTD). Until the present moment there are not any national studies that evaluated mutations in the gene SEPN1 in Brazilian patients with myopathy related to selenoprotein N1. This study is a PhD thesis and will be presented in the form of two scientific articles: the first is a literature review about the next generation sequencing in the study of the myopathies related to selenoprotein N1 and the second shows the results of the the next generation sequencing in the study of Brazilian patients with myophathies related to selenoprotein N1, and the study of these patients for others genes related to neuromuscular diseases. Objective: To evaluate the presence and characterize the mutations in the SEPN1 gene in Brazilian patients with myophathies related to selenoprotein N1, correlate the mutations to clinical and histopathological findings, thereby checking mutations in some others genes related to neuromuscular diseases that can show similar phenotypic characteristics to the myopathies related to selenoprotein N1. Methodology: 19 patients were included with myopathies related to SEPN1 from 16 different families. Among these, 14 were classified as RSMD, four with Mm, and one with CFTD. The clinical, muscular histopathologics (histological reactions and muscle histochemical) and molecular findings were evaluated for the characterization of mutations in the SEPN1 gene to research and identify mutations in the SEPN1 gene as well as in others genes included in the next generation sequencing technique that include the 61 principal genes related to neuromuscular diseases. We conducted family segregation studies of some families by Sanger sequencing. Results: The molecular study revealed mutations in 12 families. Family 1 : one patient with classic phenotype Mm , with one new mutation (c.1010G>T) in compound heterozygous with one pathogenic mutation already described (c.1384T>G) in SEPN1 gene. Families 2, 3 , 4, and 15: four unrelated patients with RSMD phenotype, showed insertion of a base out of phase (c.713-714insA) , three of them in compound heterozygous with other pathogenic mutations, one being a new mutation (3'UTR: c.53G>T) and homozygous (case 18) Family 5: One patient with Mm prenatal form with arthrogryposis showed a missense mutation in heterozigose (c.583G>A) in which the complementary change was not identified. Family 16: A patient with Mm was detected with a pathogenic mutation (c.1406G>A) in compound heterozygosity with a new mutation c.1396C>T. Family 14: One patient with CFTD showed insertion of 12 bases in phase (c.316-317 Ins.12bp), this insertion was considered a polymorphism. In this patient was a mutation detected in compound heterozygosity (c.6469G>A/c.9457G>A) in the RYR1 gene. Family 12: three siblings with with RSMD phenotype , were identified with an insertion in frame, three base pairs, in heterozygous (c.438-439ins3bp), it was considered as a polymorphism. In this family a pathogenic mutation was detected in LAMA2 gene in compound heterozygosity with a new mutation (c.1259delA). In the families 10 and 11 were mutations detected in compound heterozygosity in the COL6A1 e COL6A3 genes, in the family 10, both mutations were described as pathogenic (c.6859delG/ c.6064-5G>A) and in family 11 was one pathogenic mutation (c.850G>A) detected in compound heterozygous with a new mutation (c.2959G>A). Conclusion: myopathies related to selenoprotein N1 showed wide phenotypic and genotypic variability. 12 pathogenic mutations were detected in SEPN1 gene in 7 patients with RSMD and Mm, among them 4 didnt have registers in the medical literature. In Addition, it was possible to detect 10 mutations in 7 patients in 5 others genes related to neuromuscular diseases that were included in a NGS panel, being, 8 already described as a pathogenic mutations and, two were considered as new mutations. The molecular analysis could help to confirm the diagnosis of complex diseases that show wide genetic and phenotypic variability, as well as genetic counseling of the families.