Transcriptional regulation of post-embryonic neuronal maturation

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PROJECT SUMMARY During the complex and intricately-timed sequence of nervous system development and maturation, significant and persistent disruptions to the dynamic regulatory process through genetic and environmental risks can result in neurodevelopmental disorders. Neuroscience research has contributed much to our understanding of early neural development in the embryonic and perinatal periods including neuronal specification, neuronal migration, axonal guidance/outgrowth, and synaptogenesis. The period from early post-natal life to young adulthood is equally critical for proper development of the mature brain, as extensive structural and behavioral plasticity are observed during these periods. However, much less is known about the molecular regulatory mechanisms underlying neuronal maturation during post-natal development. In my post-doctoral work/K99 phase of the award, I developed and optimized a method to isolate single neuron types for genomics profiling. Using this method, in combination with the genetic amenability of the C. elegans system, I profiled the transcriptome and chromatin accessibility of the nervous system throughout early post-natal development to young adulthood and identified a conserved pathway, initiated by the microRNA lin-4 (mir-125 in vertebrates), that controlled many but not all developmental-regulated, neuron-specific gene expression changes that underlie neuronal maturation. In Aim 1, using the genomic profiling data as an entry point, I will take a 2- pronged approach to identify additional, novel regulators of neuronal maturation. First, I will implement bioinformatics tools to extract common cis-regulatory motifs from developmentally regulated genes and predict/test candidate transcriptional regulators. Second, using validated developmentally-regulated gene reporters from my profiling, I will conduct unbiased forward genetic screens to identify novel regulators of neuronal maturation. In Aim 2, I will use advanced neurotechnology tools to examine the role of environmental stimuli (sensory-induced neuron activity) on neuronal maturation. First, I will examine how acute and chronic inhibition of activity in target neurons, during different developmental windows, affects single neuron developmental transcriptomes and chromatin accessibility. In addition, the interaction between pathways regulating neuronal maturation through environmentally-induced activity versus intrinsic genetic mechanisms will be examined using approaches as in Aim 1. The proposed research will increase our understanding of the genetic and environmental regulatory mechanisms underlying normal post-natal neurodevelopment, improve our understanding of the etiology of neurodevelopmental disorders, and reveal novel therapeutic targets. The successful completion of this project will provide a platform for future experiments aimed at understanding gene-environment interplay in the transcriptional regulation of nervous system development and function.