Abstract
Somatic mutations accumulate in multiple organs and tissues during aging and are a known cause of cancer. Cellular senescence is a possible cause of functional decline in aging, yet also acts as an anticancer mechanism in vivo. Here, we compared somatic mutation burden between early passage and deeply senescent human fibroblasts using single-cell whole-genome sequencing. The results show that single-nucleotide variants (SNVs) and small insertions and deletions (INDELs) are increased in senescent cells by about twofold but have the same mutational signature as early passage cells. The increase in SNVs and INDELs can be explained by increased replication errors due to the increased number of cell divisions senescent cells are likely to have undergone. By contrast, a stark increase of aneuploidies was observed in deeply senescent cells, with about half of all senescent cells affected but none of the early passage cells analyzed. These results indicate that large chromosomal events rather than small base substitutions or insertions and deletions could be mechanistically linked to cellular senescence.