Absence of cyclin-dependent kinase inhibitor p27 or p18 increases efficiency of iPSC generation without induction of iPSC genomic instability.

Mechanisms underlying the generation of induced pluripotent stem cells (iPSC) and keeping iPSC stability remain to be further defined. Accumulated evidences showed that iPSC reprogramming may be controlled by the cell-division-rate-dependent model. Here we reported effects of absence of mouse p27 or p18 on iPSC generation efficiency and genomic stability. Expression levels of cyclin-dependent kinases inhibitors (CDKIs), p21, p27, and p18 decreased during iPSC reprogramming. Like p21 loss, p27 or p18 deficiency significantly promoted efficiency of iPSC generation, whereas ectopic expression of p27, p18, or treatment with CDK2 or CDK4 inhibitors repressed the reprogramming rate, suggesting that CDKIs-regulated iPSC reprogramming is directly related with their functions as CDK inhibitors. However, unlike p21 deletion, absence of p27 or p18 did not increase DNA damage or chromosomal aberrations during iPSC reprogramming and at iPSC stage. Our data not only support that cell cycle regulation is critical for iPSC reprogramming, but also reveal the distinction of CDKIs in somatic cell reprogramming.