Human pluripotent stem cells (PSCs) are subject to the appearance of recurrent genetic variants on prolonged culture. We have now found that, compared with isogenic differentiated cells, PSCs exhibit evidence of considerably more DNA damage during the S phase of the cell cycle, apparently as a consequence of DNA replication stress marked by slower progression of DNA replication, activation of latent origins of replication, and collapse of replication forks. As in many cancers, which, like PSCs, exhibit a shortened G1 phase and DNA replication stress, the resulting DNA damage may underlie the higher incidence of abnormal and abortive mitoses in PSCs, resulting in chromosomal non-dysjunction or cell death. However, we have found that the extent of DNA replication stress, DNA damage, and consequent aberrant mitoses can be substantially reduced by culturing PSCs in the presence of exogenous nucleosides, resulting in improved survival, clonogenicity, and population growth.

人类多能干细胞 (PSC) 在长期培养过程中会出现反复出现的遗传变异。我们现在发现，与同基因分化细胞相比，PSC 在细胞周期的 S 期表现出明显更多的 DNA 损伤，这显然是 DNA 复制应激的结果，其特征是 DNA 复制进展缓慢，潜在的 DNA 起源激活。复制和复制叉的崩溃。与许多癌症一样，PSC 表现出 G1 期缩短和 DNA 复制应激，由此产生的 DNA 损伤可能是 PSC 中异常和流产有丝分裂发生率较高的基础，导致染色体非脱联或细胞死亡。然而，我们发现，在外源核苷存在的情况下培养 PSC 可以大大减少 DNA 复制应激、DNA 损伤和随之而来的异常有丝分裂的程度，从而提高存活率、克隆性和群体增长。