Guardians of the genome: protecting DNA from endogenous sources of damage

Mutational signatures are imprints of cell-intrinsic and extrinsic pathophysiological processes that have occurred through tumorigenesis. Experimental efforts to explore signature etiologies have produced a compendium of signatures of exogenous mutagens previously. Here, we unearth major sources of endogenous DNA damage and the genes that are critical to mitigating this innate stream of DNA damage under normal, physiological circumstances. We performed whole genome sequencing of 173 subclones of CRISPR-Cas9 knockouts of 43 genes in a human induced pluripotent stem cell system, in the absence of any added DNA damage. We reveal substitution and indel signatures that arise from those genes which are essential guardians of the genome. By detailed dissection and comparisons to cancer-derived signatures, we demonstrate interminable sources of constitutive DNA damage, and some mechanistic knowledge into how guardian genes preserve the genome. Based on these experimental insights, we develop and benchmark a tool for clinical classification of tumor samples.

• 173 samples
• DAC: EGAC00001000205
• Technology: HiSeq X Ten