Limiting replication stress during somatic cell reprogramming reduces genomic instability in induced pluripotent stem cells

TLDR

Induced pluripotent stem cell generation from adult somatic cells is a major advance, yet genomic instability in iPSC is frequently observed and its causes remain largely unclear. We demonstrate that reprogramming factor expression triggers replication stress, and that boosting CHK1 activity or adding nucleosides during reprogramming lowers this stress, thereby reducing DNA damage, genomic rearrangements, and improving iPSC generation efficiency in both mouse and human cells.

Abstract

The generation of induced pluripotent stem cells (iPSC) from adult somatic cells is one of the most remarkable discoveries in recent decades. However, several works have reported evidence of genomic instability in iPSC, raising concerns on their biomedical use. The reasons behind the genomic instability observed in iPSC remain mostly unknown. Here we show that, similar to the phenomenon of oncogene-induced replication stress, the expression of reprogramming factors induces replication stress. Increasing the levels of the checkpoint kinase 1 (CHK1) reduces reprogramming-induced replication stress and increases the efficiency of iPSC generation. Similarly, nucleoside supplementation during reprogramming reduces the load of DNA damage and genomic rearrangements on iPSC. Our data reveal that lowering replication stress during reprogramming, genetically or chemically, provides a simple strategy to reduce genomic instability on mouse and human iPSC.