Recent evidence suggests that environmental factors causing somatic mutations during the lifetime have a more crucial role, not only in cancer but also in other common diseases, including heart failure. Recent studies have also shown that somatic single nucleotide variants (sSNV) accumulate even in nondividing cells, such as neurons in the human cortex, resulting in thousands of sSNV per neuronal genome by old age. However, genomic DNA changes in aging cardiomyocytes (CM) remain poorly understood. The accumulation of somatic DNA mutations over time has recently been demonstrated to be a hallmark of aging in many human cell types. The current study aims to determine the landscape and role of somatic mutations in aging and cardiac disease by adopting a new technique that allow deep whole-genome sequencing of DNA isolated from single CM taken from the frozen postmortem heart.
The first Aim of this study is to evaluate the somatic mutational burden (sSNVs) in aging CM genome. We will also compare CM mutational burden with postmitotic cells from another organ (neurons) to define differences in accumulation rate during aging. In the second Aim, we will ask what are the mutational signature and the mechanisms of mutation formation in the aging human heart and if the heart mutational signature is different than the brain mutational signature. Further to recapitulate the mutational signature and related phenotype in the heart we will directly induce oxidative stress in an in vitro culture model of primary CMs.
The final Aim will focus on evaluating the genotoxic effect of radiation in CMs after childhood radiation therapy and the role of radiation in premature aging. The proposed research is significant for the comprehensive, results-based development of strategies for understanding natural aging and disease progression in the human heart. Together with the planned characterization of mutational signatures, the anticipated results may provide knowledge to develop new strategies for preventing the heart disease associated with aging. The proposed study is only possible because of a series of innovations that are, at this time, uniquely available to our research team, 1) a novel method to isolate single CM nuclei from frozen myocardium based on CM ploidy and nuclei cardiac troponin T expression. 2) A major breakthrough by developing ?LiRA? and ?PhaseDel? algorithm to call sSNV and sSV confidently from tetraploid cells that considers cell-specific depth distributions of DNA sequencing and allele-dropout rates in scWGS data. For the first time, our study will reveal the landscape of somatic mutations, genomic changes during aging and after radiation therapy in human heart muscle cells in a single-cell resolution. In the long term, this study will provide insights that might allow blocking some of the mutational processes ameliorating age-related myocardial dysfunction.
Epidemiological studies clearly show that advanced age is the most important risk factor for cardiovascular disease, but we have an incomplete understanding of how aging promotes cardiovascular disease progression. The accumulation of somatic DNA mutations over time has recently been demonstrated to be a hallmark of aging in many human cell types. The overarching goal of this proposal is to define the extent of somatic mutations in aging human cardiomyocytes, provide an understanding of the mutational processes acting on aging human cardiomyocytes, and explore the link between somatic mutational burden and cardiovascular pathologies, for developing new strategies to treat millions of adults with heart disease associated with aging.
