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. Author manuscript; available in PMC: 2018 Jan 22.
Published in final edited form as: Neuron. 2017 Jan 4;93(1):80–98. doi: 10.1016/j.neuron.2016.11.036

Figure 1. C. elegans ventral nerve cord motor neurons.

Figure 1

A: Cholinergic MN classes in C. elegans VNC and their relative positions and morphology. Numbers in brackets represent the number of individual MNs in each class.

B: Unique combinations of effector gene expression define each unc-3-expressing MN class (as represented by different colors). As with the shared genes of the ACh pathway, class-specific genes are unc-3-dependent since their expression is lost in unc-3 mutants (bounded by red margin). Color-filled rectangles represent expression in the corresponding class; grey rectangles represent absence of expression; superimposed diagonal stripes indicate dim expression.

C: UNC-3 is a terminal selector which coordinately regulates the expression of class-specific as well as shared effector genes in cholinergic MNs. This co-regulation is achieved via phylogenetically conserved binding sites, termed COE motifs, found within the cis-regulatory region of these genes.

D: The co-activator versus repressor models of regulation: hypothetical models of how UNC-3 selectively controls the expression of class-specific genes. Black and color-filled circles indicate gene is expressed; grey-filled circles indicate gene is not expressed. Class-specific co-activators (A1, A2) and repressors (R1, R2).