The cdk inhibitor p27Xic1 is required for differentiation of primary neurones in Xenopus.

We have investigated the role of the cyclin-dependent kinase inhibitor, p27(Xic1), in the coordination of cell cycle exit and differentiation during early neurogenesis. We demonstrate that p27(Xic1) is highly expressed in cells destined to become primary neurones and is essential for an early stage of neurogenesis. Ablation of p27(Xic1) protein prevents differentiation of primary neurones, while overexpressing p27(Xic1) promotes their formation. p27(Xic1) may enhance neurogenesis by stabilising the bHLH protein, neurogenin. Moreover, the ability of p27(Xic1) to stabilise neurogenin and enhance neurogenesis localises to an N-terminal domain of the molecule and is separable from its ability to inhibit the cell cycle.