Figure 7.

A Pathway by which Pax6 Regulates Cortical Progenitor Cell Cycles

In this model, Pax6 directly represses Cdk6 expression and, either directly or indirectly, the expression of other cyclins (Ccnds)/Cdks. This limits the hyperphosphorylation of pRb, which is catalyzed by cyclin/Cdk complexes. This limits the release of E2F transcription factors, which bind to pRb. This limits the expression of genes such as Cdc6 and Mcm6, which promote G1 to S phase transition, and Ccnd1 (Cyclin D1), thereby dampening a positive feedback loop that would promote proliferation.