Ancillary reproductive health projects to existing large and/or longitudinal studies Sperm and egg cells carry genetic and epigenetic information from parents to offspring, serving as a link between the past, present and future of a species. Unlike oocytes and somatic cells, which package their DNA with histones, the DNA of mature sperm is bound by protamines, highly basic and rapidly evolving proteins that are essential for the compaction of paternal chromatin. This differential packaging traces back >500 million years, but the biological and functional significance of protamine protein packaging remains poorly understood. Here we identified a functional role for protamine proteins in coordinating proper embryonic development. This proposal aims to develop additional molecular genetic tools to dissect the role of protamines in fertility, early development, and evolution. Together, the findings presented here will increase our molecular understanding of these ancient, yet rapidly evolving proteins and may overturn the long-held dogma of their presumed function.