HIF1A and brain ischemia: Recent observations suggest that apoptosis of neurons after brain ischemia is strongly associated with Cdk5 hyper-activation mediated by its activator p25 [9], however, normal signaling through the Cdk5/p35 complex promotes neuronal survival, whilst inhibition of normal Cdk5 activity may inhibit Hif-1α accumulation and concomitantly induce neuronal cell death [26].