An antagonistically pleiotropic gene regulates vertebrate growth, maturity, and lifespan.

The antagonistic pleiotropy theory of aging predicts genetic trade-offs between early-life and late-life fitness. However, empirical evidence for such trade-offs in vertebrates remains scarce, particularly from causal genetic experiments. Here, combining genetic perturbation with longitudinal phenotyping in the turquoise killifish (Nothobranchius furzeri), we identify vestigial-like 3 (vgll3), previously linked by GWAS to age at maturity in humans and male Atlantic salmon, as a gene with antagonistically pleiotropic effects. Selective disruption of vgll3 isoforms accelerates male growth and maturation in a dose-dependent manner. Transcriptomic and cellular analyses indicated increased cell division, corroborated in vivo by elevated germline and intestinal stem-cell proliferation. However, early-life maturation incurs a late-life cost, linked to altered DNA damage response. Older mutant males develop melanoma-like tumors, validated via transplantation into immunodeficient rag2 models, and exhibit a shortened lifespan. Thus, we identify vgll3 as a key regulator of life-history variation with antagonistic effects across ages, balancing early-life fitness against late-life mortality.