Figure 4.
Illegitimate clustering of extrasynaptic L-AChRs in rsu-1 mutant. A, Diagram highlighting the position of an SABD axon relative to the most anterior muscle cells of a dorsal quadrant. Muscle cells (green) are numbered according to their position in the quadrant. SABD, Cyan; L-AChRs, red. B, Schematic of C. elegans head region. SABVR, SABVL, and SABD are shown in different shades of blue. The pharynx is shown in gray. Dashed rectangle matches with the region in A. C, Confocal projections of the SABD region of wild-type and rsu-1(kr251) young adults expressing a presynaptic marker (VAMP, jsIs42[punc-4::snb-1::GFP]) and the L-AChR reporter (unc-29::tagRFP knock-in). Synaptic clusters are apposed to presynaptic varicosities (between arrowheads). In the wild type, diffused extrasynaptic receptors cover muscle cell 2 and the intercellular junction between muscle cells 4 and 6 (see also A). In rsu-1(kr251), aggregates of L-AChRs are visualized in extrasynaptic areas. D, Quantification of UNC-29–tagRFP fluorescence levels at SAB synapses in the wild-type and rsu-1 mutants. E, Labeling of cholinergic terminal (VAChT, anti-UNC-17 immunofluorescence), L-AChRs (persistent unc-29::tagRFP fluorescence after fixation), and GABAARs (anti-UNC-49 immunofluorescence) at the dorsal cord in wild-type and rsu-1(kr251) young adults. F, Synaptic clustering of L-AChRs (unc-29::tagRFP knock-in) was evaluated at the dorsal cord in wild-type and rsu-1(kr251) young adults. Quantification data are presented as means ± SEM; N indicates number of worms; Student's t tests between genotypes: *p ≤ 0.05; ***p ≤ 0.001; NS, not significant. Scale bars, 10 μm.