Figure 1

Birth and melanopsin expression of ipRGCs. (A,B) The birthdates of ipRGCs were compared to Brn3a-positive RGCs (representative images in (A), paradigm in (B)). (C) For each time point, we determined the proportion of ipRGCs labeled with EdU; asterisks indicate significant difference between ipRGCs and Brn3a (t-test, P < 0.05). Representative sections with double-labeled RGCs (yellow arrowheads) and EdU-negative RGCs (white arrows) from postnatal day 0 (P0) retinas pulsed with EdU at embryonic day 15 (E15) are shown in (A). Note that the ipRGC marker beta-galactosidase (β-gal), is cytoplasmic, while Brn3a and EdU are nuclear. For all EdU time points, n = 3 to 4 retinas per time point, mean ± standard error of the mean. (D-F) Melanopsin (Opn4) expression begins at E15 based on immunofluorescence (D), and the Melanopsin^Cre/+;Z/AP (E) and Melanopsin^tauLacZ/+ genetic labeling methods (F). The Melanopsin^Cre/+;Z/AP labels all ipRGC subtypes and does not depend on the melanopsin locus for signal strength. Arrows in D-F denote migrating cells. GCL; Ganglion Cell Layer and RPE; Retinal Pigmented Epithelium. (G) Coronal sections from Melanopsin^tauLacZ/+ mice show an initial lack of ipRGCs in the periphery at E15, which is entirely filled in by P0 (arrows; D, dorsal; V, ventral). Note the lack of X-gal staining within the central optic nerve at E18 (G, green arrowhead). Scale bars: 50 μm (A,D-F); 100 μm (G).