Mulcahy, Ben et al. (2017) International Worm Meeting "The Dynamics of Synaptic Remodeling: insights from the C. elegans Motor Circuit."

Holmyard, Douglas, Christensen, Ryan, Lichtman, Jeff, Koh, WanXian, Witvliet, Daniel, Schroff, Hari, Mitchell, James, Qu, Yixin, Chisholm, Andrew, Samuel, Aravi, Bermant, Peter, Schalek, Richard, Zhen, Mei, Mulcahy, Ben, Chang, Maggie, Fetter, Rick

[International Worm Meeting, 2017]

During development, neural circuits undergo constant changes: they incorporate new neurons, and maintain, prune or remodel existing synapses. The small and rapidly developing nervous system of C. elegans allows us to address the developmental dynamics of synapses and neurons in the context of an intact neural ensemble. The vast majority of C. elegans postembryonic neurons are motor neurons. Previous studies suggest that at least one group of motor neurons, DD, reverse their neurite polarity entirely: they innervate ventral body wall muscles in the first larval stage, whereas they innervate dorsal muscles in adults. Their role of innervating ventral muscle is taken over by a group of post-embryonically born motor neurons, VD. Precisely how and when such processes occur, without disrupting motility as the motor circuit transitions into the adult form, is poorly described. We used serial section electron microscopy to reconstruct DD and VD motor neurons across development to define the beginning and ending of remodeling. We identified a series of elegantly coordinated synaptogenesis and remodeling events where synaptogenesis events follow different sequential orders for embryonic (DD) and post-embryonic (VD) neurons. Developing VD neurons have some interaction with DD neurons that may help to guide neurite extension and synaptogenesis. These events implicate an elegant mechanism that allows a gradual and seamless transition of the motor circuit to take place without disrupting its functional output.