The Y-chromosome is frequently lost in hematopoietic cells, representing the most common somatic mutation in men. However, the mechanisms regulating mosaic loss of chromosome-Y (mLOY), and its clinical relevance, are unknown. Using genotype array intensity data and sequence reads in 85,542 men, we identify 19 genomic regions (P<5x10-8) associated with mLOY. Cumulatively, these loci also predicted X-chromosome loss in women (N=96,123, P=4x10-6). Additional epigenome-wide methylation analyses in whole blood highlighted 36 differentially methylated sites associated with mLOY. Identified genes converge on aspects of cell proliferation and cell-cycle regulation, including DNA synthesis (NPAT), DNA damage response (ATM), mitosis (PMF1-CENPN-MAD1L1) and apoptosis (TP53). We highlight shared genetic architecture between mLOY and cancer susceptibility, in addition to inferring a causal effect of smoking on mLOY. Collectively, our results demonstrate that genotype array intensity data enable a measure of cell-cycle efficiency at population scale, identifying genes implicated in aneuploidy, genome instability and cancer susceptibility.</p
