Project Summary The specification of neurons from stem cells is a complex process involving the interpretation of the genetic and epigenetic landscape by proteins. The three-dimensional organization of chromatin within the nucleus is an increasingly recognized contributor of this landscape. Although there is a growing understanding of the general principles of DNA folding and functional genomic domains, how developmentally dynamic DNA folding patterns relate to the formation of neurons in vivo remains unexplored. In recent years, disruption of three- dimensional chromatin organization has been shown to lead to complex congenital diseases including a neurological degenerative disorders and skeletal abnormalities, solidifying the role of nuclear organization in development and disease. This proposal aims to characterize the organization of chromatin as it relates to an in vivo model of neurogenesis, the mouse olfactory epithelium, an organ essential for complex behaviors such as mating, communication, and toxin avoidance in both mice and humans. The availability of stem cells, progenitors, and mature neurons throughout the life of the mouse and the stratified organization of these cells presents a tractable system for isolating pure populations of developing neurons. This proposal first aims to characterize the chromatin reorganization that accompanies the development of these neurons by sorting pure populations of the aforementioned developmental cell types. Although mature olfactory sensory neurons are largely specified by the same developmental program, neurons are unique in that they stochastically express one olfactory receptor from a pool of approximately 2800. Recent in vitro studies suggest considerable nuclear architecture heterogeneity amongst clonal cell populations, but how this relates to clonal populations of functioning neurons remains unknown. By isolating mature neurons expressing one olfactory receptor, the extent of stereotypy of nuclear organization for a specific cell type will be interrogated. Lastly, this proposal aims to identify the molecular substrates of chromatin reorganization as it occurs in neurogenesis. Using established mutant cells lines that disrupt differentiation of the olfactory epithelium, the contribution of various developmental transcription factors on the nuclear architecture will be examined to identify specific regulators of nuclear reorganization. Overall, this proposal will further the mechanistic understanding of three-dimensional reorganization of chromatin during the development of unique cells of the nervous system.