Glial development and function in the nervous system of Caenorhabditis elegans

Abstract

The nematode, Caenorhabditis elegans, has served as a fruitful setting for understanding conserved biological processes. The past decade has seen the rise of this model organism as an important tool for uncovering the mysteries of the glial cell, which partners with neurons to generate a functioning nervous system in all animals. C. elegans affords unparalleled single-cell resolution in vivo in examining glia-neuron interactions, and similarities between C. elegans and vertebrate glia suggest that lessons learned from this nematode are likely to have general implications. Here, I summarize what has been gleaned over the past decade since C. elegans glia research became a concerted area of focus. Studies have revealed that glia are essential elements of a functioning C. elegans nervous system and play key roles in its development. Importantly, glial influence on neuronal function appears to be dynamic. Key questions for the field to address in the near- and long-term have emerged, and these are discussed within.

Figure 1.

Three flavors of C. elegans glia. (A) Schematic depicting the amphid sensory organ. Red, neurons; green, AMsh glial cell; and blue, AMso glial cell. Extracellular compartment formed by glia, yellow. (B) Schematic depicting the nerve ring and associated glia. Red, axons; light green, four CEPsh glia; and dark green, six glutamate receptor (GLR) glia. (C) A nerve ring synapse between the ALA (green) and AVE (yellow) neurons is ensheathed by CEPsh glia (red). (From White et al. 1986; reproduced, with permission, from The Royal Society © 1986.)

Figure 2.

Regulators of glial compartment size. Neuron (red) and glia (green) are indicated. The identities of the neuronal signals are not known. WASP, Wiscott–Aldrich syndrome protein.

Figure 3.

AMsh glia ablation leads to loss of AWC neuron sensory receptive ending. (A) Normal amphid sensory structure with AWC neuron (red) and AMsh glia (green) depicted. (Inset) AWC alone. (B) AWC neuron following glia ablation. Note loss of wing-like receptive ending. Scale bar, 0.5 µm. (From Bacaj et al. 2008; reproduced, with permission, from The American Association for the Advancement of Science © 2008.)

Figure 4.

Glia control neurite extension and branching. (A–D) Ablation of CEPsh glia leads to extension defects in ensheathed CEP dendrites. Scale bar, 5 μm (A). (E) Ablation of CEPsh glia also leads to defects in nerve ring axon guidance and branching of the AWC neuron. WT, wild type. (From Yoshimura et al. (2008); reproduced, with permission, from the authors in conjunction with The Company of Biologists © 2008.)