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. 2017 Jul 5;6:e25751. doi: 10.7554/eLife.25751

Figure 1. A map of subclass-specific genes provides an entry point to study MN subclass diversification.

(A) Schematic showing seven C. elegans MN classes (SAB, DA, DB, VA, VB, AS, VC), which are color-coded. Individual neurons of each class intermingle and populate three regions along the A-P axis; retrovesicular ganglion (RVG), ventral nerve cord (VNC), preanal ganglion (PAG). Axonal trajectory is shown only for one member of each class. (B) A map of effector gene expression with single-cell resolution. Each column represents an individual neuron. Genes that are shared, class- and subclass-specific are shown on the left. Cell body position and connectivity similarities and differences are also shown for each individual motor neuron. Asterisk next to mig-13 indicates additional expression (not shown) in MNs located in the VNC but anterior to vulva. (C) Inter-class versus sub-class diversification. The left panel shows known mechanisms for interclass-specification. Class-specific repressor proteins counteract unc-3’s activity, thereby generating ‘inter’-class diversity in C. elegans MNs (example of DA and VA class is shown) (Kerk et al., 2017). The right panel illustrates the problem of subclass diversification: Within a given class, the mechanisms controlling the expression of subclass-specific genes and thereby generate ‘intra’-class diversity are not known (example of DA class is shown).

DOI: http://dx.doi.org/10.7554/eLife.25751.002

Figure 1—source data 1. Summary of synaptic wiring data.
(extracted from www.wormwiring.org). <> = gap junction (electrical synapse), > = chemical synapse, bwm = body wall muscle, MSN = male-specific neuron (all such connections lettered in blue). Note that only some subclass-specific connections are non-dimorphic (green), while most are sexually dimorphic (red). Only connections represented by >3 serial sections are shown. The extent of dimorphism of the VB1 neurons is not currently known because of absence of available male data.
DOI: http://dx.doi.org/10.7554/eLife.25751.003
elife-25751-fig1-data1.docx (113.2KB, docx)
DOI: 10.7554/eLife.25751.003

Figure 1.

Figure 1—figure supplement 1. Validation of MN subclass-specific gene expression.

Figure 1—figure supplement 1.

Transgenic gfp reporter animals for sra-36, avr-15, flp-18, ser-2, itr-1, and egl-5 were crossed with subclass-specific red fluorescent markers (ser-2, glr-4) or a marker that labels all cholinergic MNs (cho-1). Co-localization of red and green fluorescence, axonal anatomy, time of birth and the relative location and order of neurons along the A-P axis allowed for identification of MN subclasses expressing the respective reporter.
DOI: http://dx.doi.org/10.7554/eLife.25751.004