Análise in silico de variantes genéticas nos genes REV1 e POLI em pacientes portadores de Síndrome Mielodisplásica.

Abstract

Myelodysplastic Syndromes (MDS) comprise a group of clonal diseases that affect hematopoietic precursor cells and result in an inefficient hematopoietic process with distinct clinical occurrences, such as peripheral cytopenias, dysplasias of one or more cell lines and progression to acute myeloid leukemia. The diagnosis occurs more commonly in elderly individuals over the age of 60 years, with an incidence of up to 50 cases per 100,000 inhabitants/year. It is believed that the chromosomal alterations and gene mutations involved in the pathogenesis of MDS, present in up to 80% of cases, are consequences of DNA damage caused after exposure to genotoxic agents, chemotherapeutics and environmental toxins, in addition to risk factors such as smoking and obesity, thus giving rise to genomic instability. DNA repair mechanisms act on single- and double-stranded lesions, however, when these can not be repaired, the damage tolerance mechanism is activated to avoid stalling of the replicative process. By employing specific DNA polymerases, the Translesion Synthesis (TLS) mechanism represents an important pathway that allows passage through and beyond bulky DNA lesions, however, this mechanism is error-prone and has mutagenic potential. The aim of the present study was to analyze, using in silico tools, the genomic profile and pathogenicity of genetic variants identified in the genes REV1 and POLI, which encode TLS DNA polymerases, in patients with Myelodysplastic Syndrome, in order to seek potential biomarkers for MDS. 14 patients diagnosed with MDS in a tertiary referral hospital were included in the study. Cytogenetic analysis was performed by G-Banding and the genetic variants were obtained by target sequencing (NGS Target Sequencing), different databases were used for annotation and classification of variants, and in total 5 different bioinformatics tools were used for in silico analysis of pathogenic potential. For the REV1 gene, we identified 48 variants, of which 17 were classified as pathogenic, in addition, p.Glu571Asp and p.Glu1184* variants, which obtained maximum pathogenicity prediction, were detected in all 14 patients. Regarding REV1, high-risk patients diagnosed with MDS - EB 1 and MDS - EB 2 that showed karyotypes with aneuploidies and del(7q) had a higher frequency of mutations, with high pathogenic potential, compared to low-risk patients with MDS RS-SLD and MDS-MLD showing normal karyotypes, which had a low frequency of mutations, with low pathogenic potential. As for the POLI gene, it was possible to identify 28 variants, among them, 9 were classified as pathogenic and the p.Glu122Asp, classified as deleterious by all algorithms, was detected in 9 patients. Regarding this gene, high-risk patients diagnosed at an advanced stage (SMD EB-1 and MDS-EB 2) that showed karyotypes including aneuploidies and del(7q) had a higher frequency of mutations, totalizing a very high predictive pathogenicity score, on the other hand, low-risk patients with early-stage disease had a low frequency of mutations, but with high pathogenic potential. The present study allowed us to trace important associations between the accumulation of variants found in REV1 and POLI genes and the progression of clinical conditions in MDS, thus pointing to a possible connection between the failure of the TLS mechanisms, caused by deleterious mutations, and the pathogenesis and evolution of this disease.