PROJECT SUMMARY Many monogenic diseases strike prior to or soon after birth and cause significant morbidity and mortality. In utero genome editing (IUGE) takes advantage of normal fetal properties, including small size, abundant progenitor cells, and immature immune system, to safely and efficiently institute the genome editing therapeutic prior to the onset of pathology. To fully understand the potential of IUGE and in preparation for IND applications, rigorous small and large animal studies are required to assess efficacy as well as fetal and maternal safety. The In Utero Small and Large Animal Resource Core will provide the knowledge and technical expertise required to design, implement and analyze in vivo gene editing therapies in mouse and large animal fetal models, including nonhuman primates.