Figure 3: Genetic retinal lesions induce an expansion of the central retina and RGC projections in the SC.

(a–h) Immunohistochemical detection of EYFP+ (Cre+, green) regions on cryosections (a,d) and flat mounts (g,h) in heterozygous controls and homozygous mutant retinae at P8, counterstained with DAPI (blue). Mutant retinae have an enlarged Cre-negative domain compared with wild-type or heterozygous control animals (curved lines in a,d). (b,c,e,f) Retinal lamination is the same for regions outside (b) and inside (c) the Cre-positive areas in control animals, but differs significantly in mutant mice presenting a normal lamination outside (e), but only a single thin layer of cells in the distal Cre-positive areas (f). (i) Dorsal view of a SC at P8 of control animals, stained against EYFP. The central EYFP-negative domain illustrates the area free of temporal and nasal RGC projections. (j) Dorsal view of a SC at P8 after full fills of the contralateral eye with CTB Alexa-488. RGC axons avoid the most anterior and posterior SC domains. (k) Relative Cre-negative index in retina and SC of control and α-Del mutant mice. Quantification shows that in control mice the Cre-negative index is 0.2 in both retina and SC (n=8 retinae and SCs, same animals). In contrast, in mutant mice this index reaches values above 0.8%, but stays correlated between retina and SC (n=8 retinae, n=9 SCs, different animals). (l,m) Immunohistochemical detection of Brn3a-positive cells in retinae from α-Del mutant and Cre-negative control mice at P8. Insets (1–4) illustrate Brn3a-positive cells in central and peripheral retina as shown in the camera lucida schematics. (n) Density quantification of Brn3a-positive cells for both genotypes. Unpaired Student’s t-test. (k,n) Values are mean±s.e.m. D, dorsal; GCL, ganglion cell layer; INL, inner nuclear layer; ONL, outer nuclear layer; T, temporal. Scale bar, 500 μm (g,h,l,m) and Scale bar, 200 μm (a,d,i,j).