Abstract 9854: Somatic Mutations in Single Human Cardiomyocytes Reveal Rapid Age-Related DNA Damage and Cardiomyocyte Fusion

Abstract

Introduction: Advanced age is the most important risk factor for heart disease, yet we have an incomplete understanding of how aging promotes heart disease. Accumulation of somatic DNA mutations has been demonstrated to be a hallmark of aging in many human cell types. The underlying cause of these many aging phenotypes is likely molecular in nature, but its mechanism is not well understood. Methods: To define the effect of aging on cardiomyocytes we performed single-cell whole-genome or panel sequencing from ~1000 single cardiomyocytes from 10 individuals aged 0.4 ~ 82 yrs. Mutational signatures of aging cardiomyocytes were analyzed by non-negative matrix factorization and a cell lineage tree was constructed. Results and Conclusions: Tetraploid cardiomyocytes showed a significant increase of (somatic single nucleotide variants (sSNV) density with age ( p = 0.0027), and this age-dependent increase remained significant even after adjusting for differences in the evenness of amplification. The sSNVs were distributed broadly across the genome. We further confirmed the age-dependent trend in diploid cardiomyocytes. A consistent increase of somatic mutation burden in human heart muscle cells with age, regardless of cardiomyocyte nuclear ploidy was observed. Cardiomyocytes accumulate age-related SNVs at rates higher than those previously described in other noncycling cells like neurons. Signature analysis reveals that cardiomyocyte SNVs display distinctive signatures of mutagenic processes, including increased oxidative stress, defective mismatch repair. A cell lineage tree, constructed from shared somatic single nucleotide variants, revealed that many polyploid cardiomyocytes derive from multiple clonal origins, implicating cell fusion as a major mechanism contributing to polyploidization. Since age-accumulated sSNVs create many damaging mutations, the fusion of clonally distinct cells to form multiploid cardiomyocytes provides a mechanism of genetic compensation that may minimize the complete knockout of essential genes during aging. Age-related accumulation of cardiac mutations provides a paradigm to understand the influence of aging on cardiac dysfunction.