Its transcriptional activity is enhanced by CCND3 and slightly inhibited by CDK4.Important regulator of the cerebral cortex formation, functions in cerebral cortical neuroprogenitor cells to maintain proliferation and to block differentiation into neurons. Must be down-regulated in order for such cells to exit the cycle and differentiate.Participates in the pathways by which SHH promotes cerebellar granule neuron progenitor cells proliferation.