Avalia??o da instabilidade do genoma em crian?as com fendas labiopalatinas n?o-sindr?micas

• Main Author: Xavier, Lu?za Ara?jo da Costa
• Other Authors: 91206359072
• Language: Portuguese
• Published: Universidade Federal do Rio Grande do Norte 2016
• Subjects: CNPQ::CIENCIAS BIOLOGICAS::BIOQUIMICA; Fenda labiopalatina; Micron?cleo; Instabilidade do genoma; ?cido f?lico; Polimorfismo
• Online Access: http://repositorio.ufrn.br/handle/123456789/20330

Submitted by Automa??o e Estat?stica ([e-mail]) on 2016-04-26T19:16:13Z No. of bitstreams: 1 LuizaAraujoDaCostaXavier_DISSERT.pdf: 2033184 bytes, checksum: 2e016a1123ca6a8907a0176e6866a4a7 (MD5) === Approved for entry into archive by Arlan Eloi Leite Silva ([e-mail]) on 2016-04-28T22:16:51Z (GMT) No. of bitstreams: 1 LuizaAraujoDaCostaXavier_DISSERT.pdf: 2033184 bytes, checksum: 2e016a1123ca6a8907a0176e6866a4a7 (MD5) === Made available in DSpace on 2016-04-28T22:16:51Z (GMT). No. of bitstreams: 1 LuizaAraujoDaCostaXavier_DISSERT.pdf: 2033184 bytes, checksum: 2e016a1123ca6a8907a0176e6866a4a7 (MD5) Previous issue date: 2015-07-31 === As fendas labiopalatinas n?o-sindr?micas (FL/PNS) s?o defeitos cong?nitos comuns em humanos, caracterizadas pelo desenvolvimento incompleto de estruturas que separam a cavidade nasal da cavidade oral, e s?o causadas devido a uma intera??o entre fatores gen?ticos e ambientais. Dados obtidos de estudos de caso-controle e interven??o diet?tica indicam que a suplementa??o materna com multivitaminas contendo ?cido f?lico previne o surgimento das fissuras orais. ? conhecido que o ?cido f?lico participa de fun??es celulares essenciais, como a s?ntese de nucleot?deos para o reparo do DNA, as quais contribuem para a prote??o da integridade do genoma contra eventos de danos gerados por fatores end?genos e/ou ex?genos. Inclusive, estudos revelam que a defici?ncia desta vitamina aumenta a forma??o de micron?cleos, estruturas citogen?ticas indicadoras de danos no DNA. Al?m disso, esta defici?ncia ? modulada pelos polimorfismos gen?ticos associados ao metabolismo do ?cido f?lico, comprometendo o desempenho das fun??es de estabilidade do genoma e, portanto, est?o sendo associados com o desenvolvimento de v?rios dist?rbios, dentre eles as fissuras orais. A partir deste contexto, foi conduzido um estudo transversal do tipo caso-controle n?o pareado com o objetivo de avaliar a frequ?ncia de biomarcadores de instabilidade gen?mica, sua rela??o com polimorfismos gen?ticos do metabolismo do folato, e se essas vari?veis est?o associadas com o desenvolvimento das FL/PNS em crian?as do Rio Grande do Norte, Brasil. Foram recrutados 48 pacientes fissurados e 18 crian?as controles, respectivamente, no Hospital de Pediatria Professor Heriberto Ferreira Bezerra (HOSPED)/UFRN e em escolas estaduais da cidade de Natal, RN. Com o devido consentimento dos participantes, realizou-se uma entrevista com os respons?veis para obten??o de dados epidemiol?gicos, como tamb?m procedeu-se a coleta sangu?nea das crian?as para a realiza??o dos testes. Foi executado o ensaio do micron?cleo com bloqueio da citocinese para calcular a frequ?ncia de micron?cleos (MN), pontes nucleoplasm?ticas (PN) e brotos nucleares (BN). A partir da extra??o do DNA gen?mico, avaliou-se os polimorfismos da metilenotetrahidrofolato redutase C677T e A1298C, metionina sintase A2756G, metionina sintase redutase A66G e do receptor de folato reduzido A80G pela t?cnica de rea??o em cadeia da polimerase associada ao polimorfismo de tamanho do fragmento de restri??o (PCR-RFLP). As crian?as com FL/PNS apresentaram maior frequ?ncia basal de MN, PN e BN que o grupo de crian?as controle (p < 0,001), e nenhum dos polimorfismos avaliados modificaram significativamente a frequ?ncia destes biomarcadores. Al?m disso, crian?as com FL/PNS apresentaram 2,3 vezes mais risco de exibir altas frequ?ncias de MN (p = 0,043) segundo modelo de regress?o log?stica bin?ria. A alta instabilidade do genoma nas crian?as com fissuras orais sugere que os eventos genot?xicos, em particular os que promovem quebras na dupla fita do DNA e n?o s?o devidamente reparados formando micron?cleos, representam fatores relevantes no desenvolvimento das fendas labiopalatinas n?o-sindr?micas. === 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.