Genomic Instability in Human Pluripotent Stem Cells Arises from Replicative Stress and Chromosome Condensation Defects

Abstract

Human pluripotent stem cells (hPSCs) frequently acquire chromosomal aberrations such as aneuploidy in culture. These aberrations progressively increase over time and may compromise the properties and clinical utility of the cells. The underlying mechanisms that drive initial genomic instability and its continued progression are largely unknown. Here, we show that aneuploid hPSCs undergo DNA replication stress, resulting in defective chromosome condensation and segregation. Aneuploid hPSCs show altered levels of actin cytoskeletal genes controlled by the transcription factor SRF, and overexpression of SRF rescues impaired chromosome condensation and segregation defects in aneuploid hPSCs. Furthermore, SRF downregulation in diploid hPSCs induces replication stress and perturbed condensation similar to that seen in aneuploid cells. Together, these results suggest that decreased SRF expression induces replicative stress and chromosomal condensation defects that underlie the ongoing chromosomal instability seen in aneuploid hPSCs. A similar mechanism may also operate during initiation of instability in diploid cells.

Conditional mutation of Smc5 in mouse embryonic stem cells perturbs condensin localization and mitotic progression

“…That study specified that Smc5/6 is required to resolve recombination structures formed from endogenous replication stress and late replication pausing sites. Human PSCs are prone to genomic instability due to replicative stress and impaired chromosome condensation (Lamm et al, 2015). It is likely that Smc5/6 plays a crucial role in avoiding these sources of genomic instability in PSCs.…”

“…A previous study employing human somatic RPE-1 cells has demonstrated the requirement of Smc5/6 complex for timely progression of DNA synthesis (Gallego-Paez et al, 2014). Given that DNA replication stress can further cause defects in stem cell chromosome condensation and abnormal segregation (Lamm et al, 2015), we synchronized mESCs in the G1 phase of cell cycle and observed the progression through the S phase (Fig. 4E).…”

“…PSCs also share multiple characteristics with cancer cells and are prone to acquisition of chromosomal abnormalities in cell culture. Although the underlying mechanisms that initiate genomic instability are yet to be elucidated, DNA replication stress and defective chromosome condensation, decatenation and segregation are likely contributing factors (Na et al, 2014;Lamm et al, 2015;Damelin et al, 2005).…”

Continuous chromosomal instability in human pluripotent stem cells – the role of DNA replication

“…Therefore, we set out to study replication dynamics in aneuploid hPSCs by taking advantage on the DNA combing method. We found that aneuploid hPSCs (either harboring trisomy 12, 17 or both) exhibit inherent perturbed DNA replication characterized by a slow replication rate and activation of dormant origins (6). Interestingly, a recent work showed that aneuploidy induces replication stress also in somatic cells (8).…”

“…Indeed, hPSCs harboring these recurrent aneuploidies show higher tumorigenic potential and on-going chromosomal instability similar to chromosome instability (CIN + ) cancer cells. Therefore, we were intrigued to investigate the cellular mechanisms underlying the on-going instability and tumorigenicity induced by these aneuploidies (6).…”