Project Summary Across vertebrates, early development, prior to zygotic genome activation, is dependent on maternally supplied gene products. These products will initiate molecular pathways that are necessary for the embryonic developmental programing. Mutations that disrupt the function or stability of these maternal products can be lethal to the developing embryo. Females who carry these impaired maternal-effect genes do not display an overt phenotype, but their offspring will undergo abnormal development that is independent of their genetics. Despite the importance of maternal-effect genes in early development, we have only determined the function of a small subset of maternal-effect genes via genetic approaches. In humans, defects in maternally expressed genes are expected to result in failed implantation or early pregnancy loss. The Mayo Clinic estimates that ten to twenty percent of known pregnancies are miscarried, but this percentage is likely significantly higher because early miscarriages can go undetected. This proposal aims to address the role of maternally expressed genes during the egg to embryo transition. Specifically, in Aim 1 (K99), I will perform live subcellular imaging to characterize the role of a maternally expressed chromosomal passenger complex in regulating the dynamic nature of microtubule-dependent germplasm aggregation. In Aim 2 (K99), I will be exploring the role of a maternally expressed Importin-α, Kpna7 in regulating nuclear envelope reassembly during the egg-to-embryo transition. During my R00 years, I will use a large scale maternal-crispant screen to identify novel regulators of the egg-to-embryo transition. Preliminary studies have suggested that this is an efficient way to determine the role of maternally expressed genes in development. By combining this maternal crispant screen with live subcellular imaging of the dynamic processes that are required for early development, I will start understanding the role of newly identified maternal effect genes in early embryo. My K99 training will be guided by exceptional mentors, Dr. Francisco Pelegri and Dr. William Bement, and an advisory committee, all of whom will provide support and mentorship allowing me to transition into independence. The combination of my established genetic editing skill and the training in live subcellular imaging with Dr. Bement will give me the unique skill set that is required to research the role of the maternally expressed genes in the egg-to-embryo transition. The K99/R00 award will allow me to become an independent investigator in the role of maternal products during development and will provide understanding into the genetics of infertility and early pregnancy loss.