Induced Pluripotent Stem Cell Generation-Associated Point Mutations Arise during the Initial Stages of the Conversion of These Cells

•iPSCs versus ESCs—an obvious difference in the frequency and mode of point mutations•A large number of iPSC generation-associated, not preexisting, point mutations•Heterogeneity of point mutation profiles in an iPSC clone•No common point mutations among iPSC clones

SummaryA large number of point mutations have been identified in induced pluripotent stem cell (iPSC) genomes to date. Whether these mutations are associated with iPSC generation is an important and controversial issue. In this study, we approached this critical issue in different ways, including an assessment of iPSCs versus embryonic stem cells (ESCs), and an investigation of variant allele frequencies and the heterogeneity of point mutations within a single iPSC clone. Through these analyses, we obtained strong evidence that iPSC-generation-associated point mutations occur frequently in a transversion-predominant manner just after the onset of cell lineage conversion. The heterogeneity of the point mutation profiles within an iPSC clone was also revealed and reflects the history of the emergence of each mutation. Further, our results suggest a possible approach for establishing iPSCs with fewer point mutations.

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