Figure 3.

Caenorhabditis elegans glial cells in neuronal generation and morphogenesis. (A–A′) Schematic of AMso glia in males in L3 (A) and L4 (A′) larval stages showing its cell division to generate the MCM neuron. (B) Schematic of the male PHso glia transdifferentiating into a PHD neuron during developmental L3–L4-adult transition stages. (C–C′) Diagram and image of AFD-NRE in wild-type animals with intact AMsh glial ensheathment (C), and in kcc-3 mutant animals (C′). (D–D′) Schematic (D) and image (D′) of bilateral AMsh glia–AFD. AFD-NRE staining (top arrow) is also seen as punctate fragments in the AMsh glia cell body (bottom arrow) on the side with AFD neurons present and lost in the AMsh glial cell body on the side with AFD neuron ablated. (E–E′′) Pruning by AMsh glia regulates AFD-NRE shape. Reduced pruning (ced-10 mutants) causes elongated AFD-NRE, and excess pruning (overexpress CED-10 in AMsh) causes shorter AFD-NRE. (F–F′) RME synapses localized to a specific region of the neurite in wild-type (F) are misrouted along the neurite processes in GLR innexin mutant animals (F′). (G–G′′′) Diagram and image of CEPsh glial posterior membrane sheaths directing pioneer and follower neuronal axons (G, G′), and their misdirection in glia-ablated-animals (G′–G′′′). (H–H′) Diagram and image of glial cell and axon processes in the brain neuropil of wild-type animals (H), which become truncated or misguided in kpc-1; chin-1 double mutant animals with abnormal trafficking in CEPsh glial cells, leading to reduced brain neuropil size. (I–I′′) Schematic of epithelia and AIY neuron synapses within CEPsh glia posterior process zone. Densities of AIY synapses apposing specific CEPsh glia posterior membrane sheath process regions in wild-type animals (I, I′) are decreased in animals defective for glia-secreted UNC-6/Netrin (I′) and ectopically positioned in cima-1 animals with aberrant CEPsh posterior sheath processes. (Panel C is reprinted, with permission, from Singhvi et al. 2016; D, E reprinted from Raiders et al. 2021a under the terms of the Creative Commons Attribution License; G,H reprinted from Rapti et al. 2017 with permission from the author. Schematics adapted from Singhvi and Shaham 2019 with permission from the author.)