Regulation of cortical circuit formation by subcellular compartmentalization of mRNA translation

项目总结/文摘

Project Summary/Abstract Cerebral cortex and other projection neurons extend axonal projections 103-105 times longer than their cell body diameters with exquisite precision. Growth cones (GCs) are specialized subcellular compartments that interpret axon guidance and target-derived signals, and carry out subtype-specific programs to ensure appropriate circuit and synapse formation. Because GCs extend so far from cell bodies that it takes hours to days to send molecules to them via axonal transport, GCs must be “semi-autonomous”. Local translation has been proposed as a mechanism for local control of growth cone function, but the types and diversity of locally translated mRNAs in vivo is largely unknown. More broadly, translational regulation in neurons is likely a crucial mechanism for properly establishing and maintaining long-range circuitry. Multiple neurodevelopmental (ex: Fragile X-Syndrome), and neurodegenerative (ex: ALS/FTD) diseases are caused by mutations in RNA binding proteins that both directly and indirectly disrupt several aspects of RNA processing, and culminate in altered translational output. My project addresses how translational regulation contributes to the development of subtype identity and cortical circuit formation by employing our newly-developed, low-input ribosome profiling approach to: 1) compare translational outputs and identify mRNAs in the somata that are differentially translated between multiple specific cortical projection neuron subtypes; 2) analyze the full landscape of local translation in callosal projection neuron (CPN) GCs to identify candidate regulators that are specifically locally translated in GCs; 3) functionally investigate novel, select locally GC-translated candidates in callosal projection neuron circuit formation. This project undertakes a relatively comprehensive, in vivo investigation of both subtype differences in translation, and local translation and its mechanisms in GCs. The data generated and concepts explored will provide a deep and rigorous foundation for understanding translational regulatory diversity and distinctions between neural subtypes, and the categories of mRNAs locally translated in GCs during circuit development. Beyond rigorously investigating the unique biology at the intersection of circuit formation, RNA trafficking, and translational regulation in distal neuronal subcellular compartments, it also has substantial