Signals from the reproductive system regulate somatic regeneration and vertebrate lifespan

In many vertebrate species, age at maturity is proportional to organismal lifespan. A number of theories have attempted to provide a conceptual framework for this fascinating apparent co-evolution. The ‘disposable soma’ theory predicts that costly resources that are invested in germline preservation come at the expense of repairing age-related somatic damage. On the other hand, classical experiments in C. elegans have reported that germline ablation promotes longevity via endocrine signals mediated by the somatic gonad. However, how these seemingly opposing mechanisms may affect vertebrate aging is largely unknown. Here, we use the naturally short-lived turquoise killifish (N. furzeri) to demonstrate that germline ablation can enhance damage repair and promote vertebrate longevity. This was achieved by producing a detailed single-cell atlas of the killifish ovary and testis, and generating a panel of genetic perturbations to manipulate the killifish reproductive state. Specifically, we either block costly stages of germline differentiation by mutating gonadotropins and their receptors, or alternatively, ablate the germline altogether by mutating the dnd1 gene (dead end). Interestingly, only germline ablation enhances somatic repair, particularly in females, by improving tail regeneration following genotoxic stress. To investigate the observed sexual dimorphism, we directly compare several somatic cell types from WT and dnd1 fish. We identify a surprising male-specific upregulation of pro-longevity pathways, including protein homeostasis and stress resistance. Accordingly, only germline-depleted males experience a significant extension in maximal lifespan. Together, dissecting distinct paradigms of germline manipulations, reveals a functional link between the reproductive state, damage repair, and longevity. The sex-specific effect further supports the concept that phenotypes are independent of resource allocation, and instead, could be the result of a possible endocrine effect. Our findings may therefore have exciting implications for uncoupling the reproductive state from vertebrate aging. Sexually mature one-month old fish were used, and each group varied by either sex (males or females) or genotype (wild-type or dnd1 knock-out). For wild-type fish, 3 gonads were combined from either males or female, while for dnd1 mutants, multiple fish were used per group (as the gonads are very small).