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Previous issue date: 2017-08-31 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / A forma??o de circuitos neurais durante o desenvolvimento se d? atrav?s de uma complexa intera??o entre fatores gen?ticos e ambientais, que influenciam m?ltiplos eventos como a neurog?nese, a sinaptog?nese e a mieliniza??o. Em transtornos do desenvolvimento, como o transtorno do espectro autista (TEA), intercorr?ncias nesse processo levam ? m?-forma??o da circuitaria neural e, consequentemente, a d?ficits de intera??o social, interesses restritos e movimentos estereotipados, entre outros. Recentemente, realizamos em nosso laborat?rio a an?lise do transcriptoma do c?rtex frontal no modelo animal de autismo induzido por exposi??o a ?cido valpr?ico (VPA) in utero. Observamos que ratos com 15 dias de idade (P15) apresentam aumento da express?o de genes relacionados ? estabilidade sin?ptica e redu??o de genes relacionado ? mielina, sugerindo poss?veis mecanismos moleculares para as varia??es comportamentais previamente observadas nestes animais. Portanto, o objetivo desta disserta??o foi aprofundar este estudo investigando o padr?o de mieliniza??o no enc?falo de animais tratados com VPA em diferentes idades p?s-natais (infantil: P15 e adulta: P60). Para tanto, os grupos experimental e controle foram gerados, respectivamente, atrav?s da inje??o de VPA (500 mg/kg i.p.) ou salina em f?meas gr?vidas durante o dia embrion?rio 12.5 (E12.5). A an?lise da integridade da mielina foi realizada por duas abordagens: (1) an?lise da express?o de genes relacionados ? mielina (Mobp, Plp1, Mag e Klhl1), por PCR quantitativo, no c?rtex frontal de animais em P15; e (2) quantifica??o histol?gica da distribui??o de mielina em cinco sub-regi?es do c?rtex frontal e corpo caloso de animais P15 e P60. Dos quatro genes avaliados, observamos significativa diminui??o na express?o de Mobp e Mag em animais VPA em P15. A an?lise histol?gica de mielina mostrou redu??o significativa na intensidade de marca??o no c?rtex cingulado anterior em animais VPA em P60, por?m n?o detectou diferen?a na intensidade de marca??o em animais VPA em P15 quando comparados aos controles. Conclu?mos assim que animais VPA neonatos t?m reduzida express?o de genes relacionados a compacta??o da mielina, por?m sem altera??es no conte?do lip?dico da mielina nas ?reas analisadas. Animais adultos, por sua vez, apresentaram altera??es no conte?do lip?dico da mielina no c?rtex cingulado anterior. Em conjunto, estes resultados sugerem que dist?rbios na comunica??o entre circuitos frontais neste modelo de autismo podem ocorrer inicialmente devido altera??es na organiza??o da mielina, levando a redu??es de mielina no adulto. / The formation of brain circuits during neural development occurs through the interaction between timely regulated genetic and environmental signals, which influence multiple events such as neurogenesis, synaptogenesis, and myelination. In developmental disorders, such as autism spectrum disorders (ASD), deficits in these processes may lead to neural circuitry malformations and, in consequence, to social interaction deficits, restricted interests, and stereotyped movements, among others. Recently, we performed a transcriptome analysis of the frontal cortex of an animal model of autism induced by valproic acid (VPA) in utero in our lab. We observed that VPA animals at the postnatal age 15 (P15) show an increased expression of genes related to synaptic stability and a decrease in the expression of myelin-related genes, suggesting possible molecular mechanisms for the behavioral deficits previously observed in these animals. Therefore, the aim of this Master?s thesis was to further investigate the myelination pattern in the forebrain of VPA-treated rats at different postnatal ages (infant: P15 and adult: P60). For that, experimental and control groups were generated by injecting pregnant dams with 500 mg/Kg i.p. VPA or saline, respectively, on embryonic day 12.5 (E12.5). Analysis of myelin integrity was conducted by two different approaches: (1) gene expression analysis of myelin-related genes (Mobp, Plp1, Mag, and Klhl1) in dissected samples of the frontal cortex of P15 rats by quantitative real-time PCR; and (2) histological quantification of myelin distribution in five sub-regions of the frontal cortex and corpus callosum of P15 and P60 animals. Of all genes analyzed, we observed a significant decrease in Mobp and Mag expression in P15 VPA animals. Myelin analysis showed a significant reduction in myelin staining in the anterior cingulate cortex of VPA animals at P60, but no differences were observed at P15. In conclusion, infant VPA rats showed reduced expression of genes related to myelin assembly, without alterations in the lipid content of myelin in the areas analyzed. Adult animals, in contrast, showed a decrease in lipid content of myelin in the anterior cingulate cortex. Together, these results suggest that communication abnormalities in frontal circuits in this animal model of autism may occur initially due to alterations in myelin organization, leading to myelin reduction in adulthood.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/24079 |
| Date | 31 August 2017 |
| Creators | Sousa, Carolina Ara?jo |
| Contributors | 52408493153, Velho, Tarciso Andr? Ferreira, 66992249053, Castro, Olagide Wagner de, 27306783874, Pereira, Rodrigo Neves Romcy |
| Publisher | PROGRAMA DE P?S-GRADUA??O EM NEUROCI?NCIAS, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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