Macklis, Jeffrey DTillman, Dustin Eliot2026-01-1320252025-06-052025Tillman, Dustin Eliot. 2025. Identification of growth cone molecular machinery controlling subtype-specific circuit construction during mouse cortical development. Doctoral Dissertation, Harvard University Graduate School of Arts and Sciences.32039871https://dash.harvard.edu/handle/1/42725165Precise construction of specific neural circuitry enables exquisite control over diverse nervous system functions. Circuit construction is primarily regulated by growth cones, subcellular compartments at tips of extending axons that rapidly integrate extracellular signals to control axon pathfinding, then mature into synapses. Although elegant prior work has identified molecules in neuronal cell bodies that regulate subtype-specific wiring, much less is known about downstream molecular machinery in growth cones, and how dysregulation of these intricate pathways disrupts circuit construction, leading to a range of neurodevelopmental and neuropsychiatric disorders. Here, we identify RNAs and proteins in subtype-specific growth cones from developing mouse cortex that control distinct aspects of circuit construction by engineering new approaches for in vivo subcellular investigation. We elucidate non-canonical mechanisms underlying functions of these molecules in regulating axon guidance, and highlight the power of growth cone proteomics to discover new controls over subtype-specific circuit formation. Finally, we develop a synthetic system for manipulation of molecular abundances with subtype, stage, and subcellular specificity in vivo, enhancing future functional investigations of growth cone RNAs and proteins. Together, this work demonstrates how appropriate subcellular localization of diverse molecules is essential for specific neuron subtypes to form precise circuits in vivo, and how even subtle dysregulation of growth cone molecular machinery can result in aberrant circuitry that is implicated in a wide array of neurodevelopmental and neuropsychiatric disorders.application/pdfenCircuit FormationGrowth ConesNeurodevelopmentProteomicsSubcellular BiologyTranscriptomicsNeurosciencesMolecular biologyBiologyThesis or Dissertation2026-01-130000-0002-7450-0927