Avanços tecnológicos e variabilidade genética da expansão CGG da região promotora do gene FMR1

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Universidade Federal de Goiás


X-Fragile Syndrome (FXS) is the leading cause of inherited intellectual disability in the world and the second of genetic etiology, with an estimated prevalence of 1/4000 men and 1/8000 women. The most common molecular mechanism in SXF is due to changes in the expression of the FMR1 gene, located in Xq27.3, due to CGG trinucleotide expansions in the promoter region and subsequent methylation of the gene. In spite of presenting consistent clinical findings, they are not exclusive, and the existence of carriers of alteration in the FMR1 gene without apparent clinical manifestations makes it impossible to diagnose SXF based only on the evaluation. In the present study, a methodological proposal for the molecular diagnosis of X-Fragile Syndrome was developed from the methylation-specific triple amplification of the promoter region of the FMR1 gene combined with capillary electrophoresis. Thirty-four patients with clinical indication of SXF were referred to a laboratory of the public health network. After extraction and quantification of the DNA, the samples were amplified in an optimized protocol and the products submitted to 36cm capillary electrophoresis to verify the amount of CGG repeats and the degree of DNA methylation of each sample. Pre-mutation (3%) and six complete mutations (18%) were detected, all of which revealed a high degree of methylation. Considering the clinical signs commonly presented, the patients were also analyzed for the occurrence of Autism Spectrum Disorder (ASD), which shadowing and overlapping the SXF, verifying that 100% of the individuals with complete mutation presented the phenotype. Thus, it was possible to observe small behavioral differences in the patients analyzed, indicating a lighter clinical picture regarding aspects of social interaction and stereotypies. Thus, the new methodological proposal allows to effectively determine the CGG trinucleotide expansions in FMR1 allowing an assertive diagnosis of SXF for the families of patients attended in the public health network in Goiás.



GIGONZAC, Marc Alexandre Duarte. Avanços tecnológicos e variabilidade genética da expansão CGG da região promotora do gene FMR1. 2016. 70 f . Tese (Doutorado em Biotecnologia e Biodiversidade em Rede Pró-Centro-Oeste) - Universidade Federal de Goiás, Goiânia, 2016.