Synapse Location during Growth Depends on Glia Location

Abstract

SUMMARY Synaptic contacts are largely established during embryogenesis and are then maintained during growth. To identify molecules involved in this process we conducted a forward genetic screen in C. elegans and identified cima-1. In cima-1 mutants, synaptic contacts are correctly established during embryogenesis, but ectopic synapses emerge during post-developmental growth. cima-1 encodes a solute carrier in the SLC17 family of transporters that includes Sialin, a protein that when mutated in humans results in neurological disorders. cima-1 does not function in neurons but rather functions in the nearby epidermal cells to correctly position glia during post-larval growth. Our findings indicate that CIMA-1 antagonizes the FGF receptor (FGFR), and does so most likely by inhibiting FGFR’s role in epidermal-glia adhesion rather than signaling. Our data suggest that epidermal-glia crosstalk, in this case mediated by a transporter and the FGF receptor, is vital to preserve embryonically-derived circuit architecture during post-developmental growth.

KIF1A/UNC-104 Transports ATG-9 to Regulate Neurodevelopment and Autophagy at Synapses

“…We were unable to detect any defects in the development or morphology of the glia that specifies presynaptic assembly in AIY (Figure S4A–S4F). Furthermore, visualization of the areas of contact between the glia and AIY by GFP reconstitution across synaptic partners (GRASP) (Feinberg et al, 2008; Shao et al, 2013) did not reveal defects in the AIY-glia contacts in any of the examined autophagy mutants (data not shown). We also did not detect defects in the subcellular localization of UNC-40 or MIG-10B in the examined autophagy mutants (Figure S4G–S4J).…”

Distinct Circuits for the Formation and Retrieval of an Imprinted Olfactory Memory

“…The AIY and RIA neurons required for memory retrieval were examined more closely with synaptic markers (Shao et al, 2013). Synaptic regions of AIY and RIA were superficially similar in naïve and imprinted adults, suggesting that imprinting did not lead to major structural changes in these neurons (Figure S4).…”

Coordinated morphogenesis of neurons and glia

“…2A,ii) [32-34]. Along with the previously described glia-RE contacts, these have been the focus of all existing studies on glia in the nematode.…”

“…First, in studies of glia-axon interactions, unbiased forward genetic screens have shown that synapses in the central neuropil are initially positioned by glia[32]. These synaptic positions are then maintained by epidermal signals that coordinate glial morphogenesis with larval growth [32,34]. Second, during embryonic development, morphogenesis of the sheath glial process and neuronal dendrites are coordinated, such that mutants with failures in dendrite extension show equivalent defects in glial process morphology[35].…”