Effect of removal of Fat3 from OFF-CBC type 2 on flicker ERG (Related to Fig. 4 ). (A) Schematic representation of cells types, i.e., type 2 OFF-CBCs and GABAergic ACs, that lose Fat3 expression in a Bhlhe22^CRE cKO mice (Bhlhe22^cKO). Magenta coloring represents cell type expression of FAT3. (B) VGAT immunostaining for control mice (exact genotype throughout this figure: Bhlhe22^CRE/+;Fat3^fl/+). (C) VGAT immunostaining for Bhlhe22^cKO mice (exact genotype throughout this figure: Bhlhe22^CRE/+;Fat3^fl/∆TM). (D) Quantification of the OMPL score for Bhlhe22^cKO. Controls: 0.0 ± 0.0 (n = 3 animals, 15 retinal regions); Bhlhe22^cKO: 1.0 ± 0.0 (n = 3 animals, 18 retinal regions). Each data point corresponds to a retinal region, color-coded by animal, analyzed using a nested two-tailed test. (E) DAPI and Bhlhb5 (a.k.a. Bhlhe22 gene encoded protein) staining of control mouse retinas. (F) DAPI and Bhlhb5 staining of Bhlhe22^cKO retinas. (G) Quantification of the number of nuclei per field in the IPL. Controls: 2.79 ± 0.66 (n = 3 animals, 14 retinal regions); Bhlhe22^cKO: 7.53 ± 1.20 (n = 3 animals, 15 retinal regions). Each data point corresponds to a retinal region, color-coded by animal, analyzed using a nested two-tailed test. (H) Quantification of the number of Bhlhb5⁺ nuclei per field in the IPL and GCL. Controls: 4.29 ± 0.98 (n = 3 animals, 14 retinal regions); Bhlhe22^cKO: 11.13 ± 1.34 (n = 3 animals, 15 retinal regions). Each data point corresponds to a retinal region, color-coded by animal, nested two-tailed test. (I) Representative flicker ERG raw traces for controls (n = 6 eyes) and Bhlhe22^cKO (n = 6 eyes) at 20 and 30 Hz. (J) Flicker ERG amplitude at 0.5, 10, 20, 30, 40, and 50 Hz for controls (n = 6 eyes) and Bhlhe22^cKO (n = 6 eyes). (K) Flicker ERG implicit time at 20 Hz for controls (39.7 ± 1.1 ms, n = 6 eyes) and Bhlhe22^cKO (38.3 ± 1.1 ms n = 6 eyes). Scale bars: 20 µm. Error bars: SEM.