(A–F) Sample cross-sections (A–C) and whole mounts (D–F) from Sdk1CG mice stained with antibodies to GFP and the bipolar cell (BC) marker Chx10 (A, D), amacrine (AC) marker AP2-α (B,E), and RGC marker RBPMS (C, F). Scale = 25 μm. (G) Bar graph showing density of BCs, ACs, displaced amacrine cells (dACs), and RGCs expressing Sdk1 computed from experiments like those shown in (D–F) (n = 14 fields from three animals for each experiment). (H–K) Top: GFP-stained sample Sdk1CG retinal whole mounts co-stained with antibodies to osteopontin (Ost) and neurofilament heavy chain (Nefh) (H), Brn3c (I), or Nr2f2 and calbindin (Calb) (J, K). Dotted circles indicate co-labeled neurons and scale = 50 μm. Bottom: normalized density recovery profiles and average density of co-labeled RGCs measured from corresponding experiments shown in the top row. Colored traces indicate density recovery profiles for co-labeled neurons; gray traces indicate density recovery profiles for all GFP+ cells in the GCL (n = 13–18 fields from six animals for each experiment). (L–O) Images showing the dendritic morphology of individually labeled Ost+/Nefh+ RGCs (L), Brn3c+ RGCs (M), Nr2f2+/Calb+ RGCs (N), and Nr2f2+/Calb- RGCs (O) in Sdk1CG/+ retinal whole mounts. Inset shows marker expression in the soma. (P–S) Top: images showing the laminar morphology of individually labeled Ost+/Nefh+ RGCs (P), Brn3c+ RGCs (Q), Nr2f2+/Calb+ RGCs (R), and Nr2f2+/Calb- RGCs (S) in Sdk1CG/+ retinal cross-sections. Red staining indicates VAcht, a marker for sublaminae 2 (S2) and 4 (S4) (scale = 50 μm). Bottom: inner plexiform layer (IPL) linescans measured from corresponding experiments shown in the top row. Red traces show VAChT intensity, and colored traces show reporter intensity measured from experiments like those shown in the top row (n = 6–12 fields per RGC type from more than 16 animals). (T) Summary cartoon of the Sdk1 RGC family showing Ost+/Nefh+ Onα-RGCs, Brn3c+ S1 RGCs, Ost+/Nefh- M2-RGCs, and Nr2f2+/Calb+ and Calb- ON-DSGCs.