Cell competition as a barrier for interspecies chimerism between evolutionary distant species

we develop an interspecies pluripotent stem cell (PSC) co-culture strategy and uncover a previously unknown mode of cell competition. Interspecies PSC competition occurs during primed but not naive pluripotency, and between evolutionarily distant species. We identified genes related to NF-κB signaling pathways, among others, were upregulated in loser cells and genetic inactivation of RELA, a core component of canonical NF-κB pathway, could overcome interspecies PSC competition. We further showed that an upstream regulator of the NF-κB signaling, MYD88 innate immune signal transduction adaptor, was also involved in promoting loser PSC elimination. Suppressing interspecies PSC competition via genetic perturbation of MYD88 or P65 improved engraftment of human cells in early post-implantation mouse embryos. Our study discovers a new paradigm of cell competition and paves the way for studying evolutionarily conserved cell competition mechanisms during early mammalian development. Strategies developed here to overcome interspecies PSC competition may facilitate interspecies organogenesis between evolutionary distant species, including humans. Examination of 2 different mRNA expression level of human ESC cells in co-culture and separate culture condition