Project description:Pluripotency is the capacity of early embryonic cells to make all the future lineages of the organism, and the existence of a pluripotent population of cells is important to both germ cell function and the pool of progenitor cells that enable vertebrate development to proceed over time through the process of gastrulation. Oct4, a class V POU transcription factor, is required for maintenance of pluripotency in embryonic stem cells (ESCs) and induction of pluripotency via transcription factor reprogramming. Homologues of Oct4 have been identified in other gnathostomes and classified into two different paralogues: POU5F1 and POU5F3. Here we provide evidence that these proteins are probably derived from a single POUV gene through ancient whole genome duplication events. To approach this issue, we compared the functional conservation and divergence of different POUV proteins in their capacity to support naïve pluripotency in mouse ESCs. We found a strong correlation between POU5F1 activity in naïve pluripotency and the regulation of germ cell specification programs. In contrast, POU5F3 exhibited reduced capacity to support naïve ESCs and its activity in ESCs correlated with the expression of genes associated with pre-gastrulation stages, or primed pluripotency. We detected evidence of this functional segregation as early as Sarcopterygian ancestors, based on the activities of coelacanth POUV proteins. Furthermore, we were able to identify earlier POUV homologues in lamprey and shark, indicating that the earliest point at which mammalian-level pluripotency of both POUV paralogues emerged is between the osteichthyan-chondrichthyan split and the gnathostome-cyclostome split.Taken together, our work highlights the evolutionary history of POUV activities across jawed vertebrates, suggesting that evolutionary pressure has facilitated maintenance of both paralogues over long periods of evolutionary history. In species with both paralogues, subfunctionalization of these proteins appears conserved. However, in many branches of vertebrate evolution, one of these paralogues is lost, suggesting a high level of plasticity in function and precarious balance between retaining both proteins and the overall levels of POUV activity in different developmental systems. While the conserved subfunctionalization of POUV activities evolved at some point just before the appearance of tetrapods, the additional divergent activities of this protein family appear to have evolved independently in each vertebrate lineage after gnathostome radiation.

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Maintenance of pluripotency signature in the entire ectoderm enables potential for neural crest formation

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