Patterns and Mechanisms Underlying Somatic Mutations Across Long-Lived Bats

Aging is ubiquitous across the tree of life, impacting biology at all levels. Among the hallmarks of aging, the accumulation of somatic mutations over time has been implicated in many leading causes of death including cancer10-12, heart disease4, and dementia5. However, most risk factors governing somatic mutation rates and patterns with age remain unknown. It has recently become possible to study the relationship between somatic mutation rates and longevity using comparative genomics. Cagan et al. (2022) demonstrated a negative correlation between somatic mutation rates and longevity, and identified conserved, longevity-associated mutational spectra across mammals. Yet, this study lacked the power to explore further due to both sparce taxonomic sampling and low sample sizes per species. Thus, there is an outstanding gap in our knowledge of how somatic mutational spectra relate to changes in longevity, and the genes involved in longevity- associated mutational spectra. To properly study the mechanisms governing mutation rates and patterns, one must sample many individuals from a group of closely-related species spanning a wide range of lifespans. My central hypothesis is that somatic mutation spectra unique to long-lived mammals are signatures of enhanced DNA damage repair responses that contribute to their extraordinary longevity. In order to identify the genetic mechanisms underlying longevity-associated somatic mutational spectra, I have generated matched skin tissue and cell lines from over 200 individuals across 10 species of a closely related (14 million years) clade of bats spanning a 3-fold range in lifespans, including the longest-lived bat species in North America. In Aim 1, to explore how somatic mutation rates co-evolve with longevity and identify longevity-associated mutational spectra in bats, I will use the highly sensitive NanoSeq to sequence 60 individuals across a trio of species in skin tissue samples. In Aim 2, using matched cell lines from the same individuals I will identify both cis and trans regulators of somatic mutation rates and spectra by using the massively parallel CRISPRi screen Repair-seq. As I transition towards an independent researcher position, in Aim 3 I will expand my functional work to other tissues and developmental contexts by developing induced pluripotent stem cells (iPSCs) from my collection of bat cell lines, and combine the cell type diversity of embryoid bodies with the power of Repair-seq to assess DNA damage repair mechanisms across all cell types simultaneously. This project is the first to explore how somatic mutation rates and spectra co-evolve with longevity both mechanistically and at high resolution. The foundations of this project will be the cornerstone of my research program exploring the evolution of longevity-associated traits in extraordinarily long-lived species using functional genomics. Using iPSCs from non-lethal skin biopsies will enable us to study aging processes in internal tissues as a part of longitudinal studies, enabling new avenues of research in the comparative biology of aging.