Résumé
The field of epigenetics is a fascinating research area focusing on the regulation of DNA sequence. More specifically, DNA methylation is an epigenetic mechanism vastly studied in a myriad of organisms allowing to link gene expression with phenotypic plasticity. The mangrove rivulus (Kryptolebias marmoratus) is an ideal model organism for studying the epigenetic roles in the regulation and expression of phenotypic traits, as it is one of only two vertebrates capable of self-fertilization. This ultimately allows to specifically scope epigenetic mechanisms while drastically reducing genetic variation between individuals. This work therefore aims to study the evolutionary potential of DNA methylation in two populations of the mangrove rivulus exhibiting a differential genetic background. A first approach studies the methylome in the gonads using Reduced-Representation Bisulfite Sequencing (RRBS), targeting CpG-rich DNA regions of the genome where cytosine methylation is known to be abundant in vertebrates. A second approach targets gene-specific methylation of key epigenetic actors, namely DNMT3a (DNA Methyl-Transferase 3a), MeCP2 (Methyl CpG binding Protein 2), and NIPBL (Nipped-B-like protein B) in three developmental stages of K.marmoratus, using bisulfite pyrosequencing. RRBS study on the gonads of ermaphroditic fish shows a close methylation pattern within cytosine distribution in both populations. The differential methylation of CpGs (DMCs) and of regions (DMRs) showed that 1.230% of the CpGs and 4.236% of the regions are significantly differentially methylated between the two populations on the reverse strand of DNA. Pyrosequencing analysis on the other hand reveals interestingly variable methylation between the targeted sequences. Notably, the second intron of DNMT3a and the promoter region of NIPBL demonstrated a significant effect of the 2
developmental stages on the methylation status of the studied sequences, showing progressive demethylation and increasing methylation, respectively, while progressing
through embryogenesis. Evolutionary potentials are discussed following the DNA methylation patterns discovered throughout this research. This work promotes further investigation on the contribution of DNA methylation towards phenotypic plasticity using cutting-edge technologies, especially with the mangrove rivulus which has unique natural characteristics permitting to decipher relevant epigenetic questions.
| la date de réponse | 2024 |
|---|---|
| langue originale | Anglais |
| L'institution diplômante |
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| Superviseur | Frederic Silvestre (Promoteur) |