Reprogramming of fish somatic cells for nuclear transfer is primed by Xenopus egg extract

Abstract: Somatic cell reprogramming in vitro prior to nuclear transfer is one strategy expected to improve clone survival during development. In this study, we investigated the reprogramming extent of fish fin somatic cells after in vitro exposure to Xenopus egg extract and subsequent culture. Using a cDNA microarray approach, we observed drastic changes in the gene expression profile of the treated cells. Several actors of the TGFβ and Wnt/β-catenin signaling pathways, as well as some mesenchymal markers, were inhibited in treated cells, while several epithelial markers were upregulated. This was associated with morphological changes of the cells in culture, suggesting that egg extract drove somatic cells towards a mesenchymal-epithelial transition (MET), the hallmark of somatic reprogramming in induced pluripotent stem cells (iPSCs). However, treated cells were also characterized by a strong decrease in de novo lipid biosynthesis metabolism, the lack of re-expression of pou2 and nanog pluripotency markers, and absence of DNA methylation remodeling of their promoter region. In all, this study showed that Xenopus egg extract treatment initiated an in vitro reprogramming of fin somatic cells in culture. Although not thorough, the induced changes have primed the somatic chromatin for a better embryonic reprogramming upon nuclear transfer.