CDK1 plays an important role in the maintenance of pluripotency and genomic stability in human pluripotent stem cells

Abstract

Human embryonic stem cells (hESC) and induced pluripotent stem cells (hiPSC) are characterised by an unusual and tightly regulated cell cycle that has been shown to be important for the maintenance of a pluripotent phenotype. Cyclin-dependant kinase 1 (CDK1) is a key player in cell cycle regulation and particularly mitosis; however, its role has not been studied previously in hESC and hiPSC. To investigate the impacts of CDK1 downregulation, we performed RNA interference studies which in addition to expected mitotic deficiencies revealed a large range of additional phenotypes related to maintenance of pluripotency, ability to repair double strand breaks (DSBs) and commitment to apoptosis. Downregulation of CDK1 led to the loss of typical pluripotent stem cell morphology, downregulation of pluripotency markers and upregulation of a large number of differentiation markers. In addition, human pluripotent stem cells with reduced CDK1 expression accumulated a higher number of DSBs were unable to activate CHK2 expression and could not maintain G2/M arrest upon exposure to ionising radiation. CDK1 downregulation led to the accumulation of cells with abnormal numbers of mitotic organelles, multiple chromosomal abnormalities and polyploidy. Furthermore, such cells demonstrated an inability to execute apoptosis under normal culture conditions, despite a significant increase in the expression of active PARP1, resulting in tolerance and very likely further propagation of genomic instabilities and ensuing of differentiation process. On the contrary, apoptosis but not differentiation, was the preferred route for such cells when they were subjected to ionising radiation. Together these data suggest that CDK1 regulates multiple events in human pluripotent stem cells ranging from regulation of mitosis, G2/M checkpoint maintenance, execution of apoptosis, maintenance of pluripotency and genomic stability.

Crosstalk between stem cell and cell cycle machineries

“…Loss of CDK1 in human ES cells results in a reduction of pluripotency gene expression, including the core factors OCT4, KLF4, and LIN28, and subsequently increases differentiation [33]. Additionally, these cells show increased DNA damage and ensuing apoptosis [33,34]. Similar results were found performing chemical CDK2-inhibition in human ES cells [35].…”

“…Indeed there are several examples of how the high CDK activity in ES cells may influence the pluripotency network. Loss of CDK1 in human ES cells results in a reduction of pluripotency gene expression, including the core factors OCT4, KLF4, and LIN28, and subsequently increases differentiation [33]. Additionally, these cells show increased DNA damage and ensuing apoptosis [33,34].…”

CDK1-PDK1-PI3K/Akt signaling pathway regulates embryonic and induced pluripotency

“…3 Cdk1 is also essential for meiosis in mouse oocytes, 4 and the suppression of Cdk1 leads to the differentiation of mouse trophoblast stem cells into giant cells. 5 Recently, it has been demonstrated that Cdk1/CDK1 is required for self-renewal in both mESCs and human embryonic stem cells (hESCs), 6, 7 which might be related to its interaction with Oct4. 8, 9 CDK1/CDK2 potentially regulates a large number of substrates (at least 1220) during hESC differentiation.…”

Nanotopography controls cell cycle changes involved with skeletal stem cell self-renewal and multipotency

“…Cyclin D1, cyclin B and cdc2 (CDK1) are involved in cell cycle regulation during G1 and G2/M phases [37] and have been reported to help regulate pluripotency in human embryonic/induced pluripotent stem cells [38] and were down-regulated in SSCs on SQ. Negative regulators of the cell cycle, p21 Cip1 , p19INK4D and p18INK4C ), were also down-regulated on SQ, which suggests that cell cycle progression is occurring on this surface ( i.e.…”