Avaliação da instabilidade do genoma em crianças com fendas labiopalatinas não-sindrômicas

Abstract

The non-syndromic clefts of the lip and/or palate (NSCL/P) are common birth defects in humans characterized by an incomplete development of cellular structures that separate the nasal cavity from the oral cavity, and they are caused due to an interaction between genetic and environmental factors. Data from case-control and dietary intervention studies indicates that maternal supplementation with multivitamins containing folic acid prevents the formation of oral clefts. It is known that folic acid plays a role in essential cellular functions, such as nucleotides synthesis for DNA repair, which contribute to the protection of genome integrity from damage events generated by endogenous and/or exogenous factors. In fact, studies show that a deficiency in this vitamin increases micronuclei formation, a cytogenetic structure that indicates misrepair of damaged DNA. Furthermore, this deficiency is modulated by genetic polymorphisms associated with folic acid metabolism, affecting the performance of genome stability functions and therefore, it has been associated with the development of various disorders, including oral clefts. From this context, it was planned a unpaired case-control cross-sectional study in order to assess the frequency of genome instability biomarkers, their relationship with genetic polymorphisms in folate metabolism, and if these variables are associated with the development of NSCL/P in children from a Northeast region at Brazil. For this research, it was recruited 48 NSCL/P patients and 18 control children, respectively, at the Pediatric Hospital Professor Heriberto Ferreira Bezerra (HOSPED)/ UFRN and at schools in Natal city. With the participants consent, they were interviewed with a standard questionnaire to obtain epidemiological data, and the children underwent a blood sampling for the tests. It was performed the cytokinesis-block micronucleus assay to estimate the frequency of micronuclei (MN), nucleoplasmic bridges (NPB) and nuclear buds (NB). Also, from the genomic DNA extraction, it was evaluated by PCR-RFLP the polymorphisms of methylenetetrahydrofolate reductase C677T and A1298C, methionine synthase A2756G, methionine synthase reductase A66G and reduced folate carrier A80G. Children with NSCL/P had higher baseline frequency of MN, NPB and NB than the control group (p < 0.001), and none of the evaluated polymorphisms significantly modified the frequency of these biomarkers. In addition, children with clefts had 2.3 times more risk of displaying high frequency of MN (p = 0.043) according to the binary logistic regression model. The high genomic instability in children with oral clefts suggests that genotoxic events that promote double strand breaks on DNA and are not properly repaired, thus originating micronuclei, represent significant factors in the development of non-syndromic cleft lip/ palate.