Contrasting transcriptome landscapes of rabbit pluripotent stem cells in vitro and in vivo.

Pluripotency refers to the ability for a single cell to differentiate into the three embryonic germ layers. In mice, two types of pluripotent stem cells with different features have been obtained in vitro. Naive pluripotent stem cells are derived from the inner cell mass (ICM) of early blastocyst (ESCs) or reprogrammed from somatic cells (iPSCs), while primed pluripotent stem cells are derived from late epiblast (EpiSCs). Cells in a primed pluripotency state are more prone to differentiation and only naive pluripotent stem cells form germline chimera after injection into a blastocyst. Despite numerous attempts, capturing pluripotency in domestic mammalian species has been largely unsuccessful and only primed pluripotent stem cells have been obtained even starting from early blastocyst or reprogramming somatic cells. This raises two questions: whether inner cell mass and epiblast are in naive or primed pluripotency state and what are the transcriptome features of ESCs and iPSCs in these species. To address these questions we compared rabbit ICM, epiblast, ESCs and iPSCs transcriptomes. Our results show that: (i) molecular signature of naïve and primed pluripotency may differ between mice and rabbit embryos; (ii) Genes involved in G1/S transition of the cell-cycle, actin cytoskeleton signaling, development and differentiation pathways are upregulated in ESCs and iPSCs; (iii) ICM and epiblast upregulate pluripotency associated genes and display specific metabolic features. These results denote an advanced primed state of pluripotency for rabbit ESCs and iPSCs and evidence specific functions for ICM and epiblast that are not shared by ESCs and iPSCs.