The formation of functional neural circuits depends on several neurodevelopmental processes, including the formation of growth cones to drive neurite outgrowth and branching, and synapse formation. These processes require filamentous actin (F-actin) formation and regulation. Branched F-actin dynamics are mediated by actin-binding proteins such as the Arp2/3 complex and its regulators, including Arp2/3-activating WAVEs and WASPs and Arp2/3-inhibiting Coronins. Despite this, the precise roles of many branched F-actin regulators in C. elegans neurodevelopment remain elusive, as their loss of function mutants are embryonic lethal. To directly test the functions of branched F-actin regulators in neurodevelopment, I used the auxin-inducible degron (AID) system to knock down branched F-actin regulators, specifically in neurons. Using the AID system, I found that ARX-2/Arp2, a subunit of the Arp2/3 complex, WVE-1/WAVE, POD-1/CORO7, and COR-1/Coronin-1 are necessary for synapse formation but not for maintenance in the DA9 motor neuron. Furthermore, I found that ARX-2/Arp2, WVE-1/WAVE, WSP-1/WASP, POD-1/CORO7, and COR-1/Coronin-1 are necessary for axon branch formation in the PLM mechanosensory neurons.
Sydney So-Young Ko (Thu,) studied this question.