Figure 3. RGCs also display differential dependence on DSCAM C-terminal interactions for self-avoidance.
(A–C) Melanopsin-positive intrinsically photoresponsive retinal ganglion cells are found in a mosaic pattern in wild type retinas (A), but at two weeks of age, ipRGC cell bodies in Dscam∆C/∆C (B) retinas are pulled into clusters similar to those in Dscam-/- (C) retinas. (D) Overall ipRGC density was not significantly increased in Dscam∆C/∆C retinas. (E) By DRP, cell body clustering was intermediate between Dscam+/+ and Dscam-/- retinas. Voronoi (F) and nearest neighbor (G) analyses also revealed a clear intermediate defect. Values from Dscam∆C/∆C retinas were significantly different from both control and Dscam-/- mutants. (H–J) Cdh3-GFP RGCs are mosaically spaced in control retinas (H), and this spacing is not perturbed in the Dscam∆C/∆C retinas (I), but these cells form clusters in Dscam-/- animals (J), indicating interactions mediated by DSCAM’s C-terminus are dispensable to prevent these cells from clustering. (K) Cdh3-GFP RGC overall cell density was significantly increased in Dscam-/- retinas, but not in Dscam∆C/∆C mutants. (L) A clear exclusion zone is detectable by DRP analysis in Dscam+/+ and Dscam∆C/∆C retinas. This exclusion zone is lost in Dscam-/- animals, where cell density is increased adjacent to any given cell, indicative of clustering. Similarly, Voronoi (M) and nearest neighbor (N) analyses describe a clear spacing defect in Dscam-/- but not in Dscam∆C/∆C retinas. Means ± s.e.m. are represented in D–E, K–L. Box plots represent the median, first and third quartile, range, and outliers. N = 6 retinas per genotype. *p<0.05; **p<0.01; ***p<0.001; n.s. is not significant by Tukey post-hoc test between indicated genotypes or compared to controls. Scale bar is 250 µm. Representative Voronoi domains are in Figure 3—figure supplement 1.
Figure 3—figure supplement 1. Examples of Voronoi tessellation domains in Dscam mutants.
