Naïve Pluripotency and Chimeric Competency in Rabbits and Non-Human Primates

Pluripotent stem cells (PSCs) exist in two distinct state configurations,the naive and primed states. These two states exhibitdramatic differences in their transcription and epigenetic profile,cell cycle regulation and energy production, which subsequentlyinfluence their characteristics and function. In rodents,only the naïve embryonic stem cells (ESCs) can colonise theblastocyst, contribute to the development of all tissue types, andgenerate germline chimeras. In rabbit and non-human primates,PSCs exist only in primed-like states and, consequently, theyfail to incorporate into host blastocysts and participate in embryodevelopment.We aim to develop embryo colonization-competent PSCs inrabbits and rhesus monkey for developmental studies. Protocolsoriginally developed to convert human PSCs to naïve-likepluripotency (i.e. cocktails of transcription factors, cytokinesand kinase inhibitors) were systematically applied to rabbitand rhesus PSCs. The transcriptome of the converted cells wasanalysed and compared to that of the embryo. The capacity ofthe converted cells to colonise rabbit morulas and participate inembryo development was systematically assessed. Reprogrammingprotocols originally developed in human PSCs yieldedvery variable results in rabbit and rhesus monkey. Only someprotocols yielded PSCs capable of extensive incorporation andsurvival into host embryos. A correlation was observed betweencolonisation competency and the yield of transcriptome reconfiguration.On the basis of these results, I will discuss the obstaclesto overcome for successful generation of somatic chimerasin non-rodent species.