Overexpression of CDK5 in Neural Stem Cells Facilitates Maturation of Embryonic Neurocytes Derived from Rats In Vitro

To further understand the effects of cyclin-dependent kinase 5 (CDK5) on the differentiation of neural stem cells, which were cultured and transfected with CDK5-EGFP recombinant overexpression vector (OV-CDK5 Group), successful transfection was confirmed by RT-PCR and Western blot. Our results showed that the CDK5 mRNA expression significantly increased in 6 h after transfection. Increase in the levels of the CDK5 protein expression was observed in 72 h, compared with Empty Vector Control Group (EV-CTL Group) (P < 0.01). Furthermore, in OV-CDK5 Group, the percentage of S-phase cells was significantly higher than in EV-CTL Group (P < 0.01). Differentiated cells were showed with short processes in 24 h and with obviously enlarged cell body, and extended cellular processes in 72 h, in comparison to those in EV-CTL Group (P < 0.01). In 72 h under treatment with 10 mu mol/L all-trans retinoic acid (ATRA), in OV-CDK5 Group, processes of the GFP-positive cells were reduced slightly and little GFP-positive debris was found. However, in the EV-CTL Group, processes of the GFP-positive cells were obviously shortened and deformed and much GFP-positive debris were found. Moreover, the percentage of G0/G1-phase cells was lesser, while the percentage of S-phase cells was higher than that in EV-CTL Group (P < 0.01, P < 0.01). In conclusion, our experiment suggested that CDK5 might promote proliferation and differentiation of neural stem cells, lengthen the processes of differentiated neurocytes, and accelerate morphological maturation of such cells. Furthermore, CDK5 might antagonize ATRA-induced inhibition against proliferation and differentiation in differentiated neurocytes.