Padronização da investigação molecular do gene FMR1 associado à síndrome do X-frágil em hospital universitário de Maceió/AL

Abstract

Fragile-X syndrome (FXS) is an X-linked dominant genetic condition and is the main heritable cause of Intellectual Disability (ID), with major prevalence in males. It is caused by an unstable mutation consisting of an expansion of a repeat region of the CGG trinucleotide triplet in the 5' untranslated region of the first exon of the FMR1 gene (FMRP translational regulator 1), causing hypermethylation in the gene promoter, resulting in its silencing and loss or reduction in the expression of the FMRP protein (Fragile X mental retardation protein), which is essential for the regulation of molecular mechanisms related to neural development, the connection of synapses and the maintenance of nervous circuits. This change can occur in premutation or full mutation, depending on the number of CGG repeats, and in addition to SXF as a condition in male patients with full mutation, other conditions exist and are associated with premutation in the FMR1 gene in men and women, such as Fragile X-associated tremor/ataxia syndrome and primary ovarian insufficiency (women only). Therefore, the objective of this study was to standardize a technique for the molecular investigation of FXS through the screening of the FMR1 gene, at the Laboratory of Human Molecular Genetics, located at the University Hospital Professor Alberto Antunes, of the Federal University of Alagoas (LGMH/HUPAA-UFAL) to offer it as a diagnostic test to patients with suggestive clinical features, positive family history or with some degree of ID. For this, a family with a positive family history and a clinical history suggestive of FXS was selected, and after collecting biological material, extraction of genomic DNA was carried out in the laboratory, and conventional and multiplex PCR reactions were performed, with subsequent analysis by capillary electrophoresis (ABI 3500®), and the generated electropherograms were analyzed in specific software for the analysis of fragments. From this, it was possible to confirm that the male patients of this investigated family are carriers of SXF, with full mutation in the FMR1 gene. In view of this, the standardization of the technique at the LGMH was successfully carried out and the test has been offered at the Clinical Genetics Service of the HUPAA-UFAL, within the scope of the Unified Health System, as well for patients with ID selected by active search in the capital and in other municipalities of Alagoas.