Epigenetic characterization of epiblast stem cells derived from fertilized and nuclear-transferred mouse embryos
Résumé
In the embryo, pluripotency is established after the 16 cell-stage and is maintained up to the early gastrulation stage in the epiblast, while profound epigenetic changes and pattern specification occur in the embryo. Embryo-derived pluripotent cells can be classified into two distinct states of pluripotency, naïve (mouse ESCs) and primed (EpiSCs). The former is closer to the inner cell mass of blastocyst while the latter, to the epiblast of a more advanced, pre-gastrulating stage. Reprogramming of a somatic nucleus to pluripotency using nuclear transfer (NT) can be achieved relatively efficiently. Whereas it was shown that ES cells derived from NT-embryos were undistinguishable from those derived from fertilized embryos, our previous work showed that some NT-derived EpiSC lines exhibited a subset of abnormally expressed genes. In order to better characterize the differences exhibited by NT-derived EpiSCs, we have established the methylation profile of EpiSCs by MethylCap-sequencing. Compared to the general annotation profile of methylated peaks in EpiSCs, promoter annotations are highly enriched in the differentially methylated regions (DMR) between NT and control EpiSCs. Validation of some DMRs by DNA bisulfite conversion/pyrosequencing is currently ongoing.