PESQUISA DE VARIANTES GENÉTICAS EM PACIENTES BRASILEIROS COM DISTONIA IDIOPÁTICA

• Ano de defesa: 2019
• Autor(a) principal: Camila Oliveira dos Santos Alves
• Orientador(a): Patricia Maria de Carvalho Aguiar
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Faculdade Israelita de Ciências da Saúde Albert Einstein
• Programa de Pós-Graduação: Acadêmico em Ciências da Saúde
• País: Brasil
• Palavras-chave em Português: Distonia; Variação genética; Transtornos dos movimentos
• Palavras-chave em Inglês: Dystonia; Genetic variation; Movement disorders
• Link de acesso: https://repositorio.einstein.br/publicacao/171379

Introduction: Dystonia is a movement disorder of neurological order, characterized by involuntary contractions that lead to abnormal movements and postures, or both, that can occur in an isolated part or in the whole body. Studies in dystonia have advanced due to improvement of sequencing technologies. The discovery of novel genes and pathogenic allelic variants allowed the identification of proteins involved in the pathophysiology of dystonia implicated in several metabolic pathways when dysfunctional. Actually, genetic diagnosis in dystonia is already an element used to define prognosis, useful in indication of specific treatments, especially in relation to surgical treatment, and reclassification of sporadic or familial cases considered idiopathic. Purpose: This project aimed to standardize the molecular analysis of the main genes described, identifying potentially pathogenic variants in Brazilian individuals with idiopathic dystonia, to characterizing them according their pathogenic potential and to establish genotype – phenotype correlations. Methods: Through the project “Brazilian Network for the Study of Dystonia”, 153 individuals with isolated or combined idiopathic dystonia, were investigated for allelic variants in TOR1A, TUBB4A, GCH1, TH, DDC, THAP1, SGCE, ATP1A3, PRKRA, CIZ1, ANO3, GNAL and KCTD17 genes by a custom amplicon-based assay for targeted resequencing (TruSeq® Custom Amplicon) in the MiSeq system (Illumina). The obtained sequences were aligned to human genome reference and allelic variants were characterized by in silico analysis according its pathogenic potential and correlation with the phenotype. To date, in silico homology molecular modeling was performed to evaluate the impact of variants on protein function and conformation. Results: In this study, in 16% of the probands, we identified 25 allelic variants with a possible causal contribution to dystonia in most genes investigated in the panel, including variants already established as cause of dystonia in the TOR1A, THAP1, GCH1, and PRKRA genes. Unusually, DYT-PRKRA was a major cause of dystonia in our sample, accounting for about 4% of cases, without parkinsonism. Novel variants in the CIZ1, GNAL, and KCTD17 genes correlated with the phenotype of cervical dystonia with onset in adulthood, but myoclonus described in DYT-KCTD17 cases was not observed in the proband of this study. In DDC gene, we identified a frameshift insertion and premature stop codon with high impact on protein function, according to in silico analyzes, in case of dystonia-parkinsonism. Conclusions: Through this study, it was possible to confirm the role of the TUBB4A, CIZ1 and KCTD17 genes as cause of dystonia in our sample, this being the first confirmatory study in Brazilian individuals. Unlike other studies, PRKRA was a frequent cause. In addition, we described ten novel variants characterized according to pathogenic potential. Regarding the etiology of dystonia, although functional studies are necessary to confirm the pathogenicity of the variants identified in this study, our results showed genetic causes among idiopathic cases in our sample, with greater efficacy in cases with early onset.