CDK5 and Stroke: We also examined neuronal death by TUNEL and PI staining and found that Tat-CDK5-CTM reduced the percentage of TUNEL- or PI-positive cells when compared with vehicle- or Tat-s-CDK5-CTM-treated OGD neurons (Fig. 1D and Supplementary Fig. 2A-B), suggesting that Tat-CDK5-CTM can protect against stroke damage in vitro.