Figure 4.

Labeling of ipRGCs in Crhr1-gfp retinas. A, GFP labeling of a subset of genetically identified ipRGCs in a Crhr1-gfp⁺;Opn4^Cre/+;Ai14^+/− retina. Confocal micrographs show GFP fluorescence (green, A₁), tdT expression driven by an Opn4-cre allele (Opn4-cre>tdT) (magenta, A₂), and their overlap (A₃) in the GCL of a Crhr1-gfp⁺;Opn4^Cre/+;Ai14^+/− retina. Yellow arrowheads indicate somas that exhibit overlap between both fluorescence channels. Empty arrowheads indicate tdT⁺ somas that lack GFP expression. B, Quantification of overlap between genetically labeled ipRGCs (tdT⁺) and GFP⁺ RGCs in the GCL of Crhr1-gfp⁺;Opn4^Cre/+;Ai14^+/− retinas; 20.4% of GFP⁺ RGCs are ipRGCs (top) and 86.2% of ipRGCs are GFP⁺ (bottom). C, GFP fluorescence intensity distribution of genetically labeled ipRGCs (tdT⁺) in Crhr1-gfp⁺;Opn4^Cre/+;Ai14^+/− retinas. D, Targeted recording and dye-filling of intensely GFP⁺ ipRGCs in Crhr1-gfp retinas. D₁, Confocal micrograph of an intensely GFP⁺ ipRGC (>90th percentile in distribution shown in C) dye-filled during whole-cell recording in a whole-mount Crhr1-gfp retina. D₂, Melanopsin-mediated intrinsic photocurrent of cell shown in D₁ in response to a 1 s light pulse (Φ_stim = 1.5 × 10¹⁶ Q cm⁻² s⁻¹).