Figure 2 .

Summary scheme describing Cdk2-cyclin E interactions involved in cell cycle withdrawal and arrest in OPC. Compared to proliferating OPCs (A), Cdk2 and cyclin E protein expression is not modified during reversible cell cycle arrest in G1 (B) but Cdk2-cyclin E complex formation is impaired which causes a selective decrease in Cdk2 activity. However, in differentiated cells that had permanently withdrawn from the cycle (C), protein levels, Cdk2-cyclin E complex formation and kinase activity are decreased compared to proliferating OPCs (A).