a Schematic diagram of flippase (Flp) removal of the neo-cassette and conditional excision of the floxed HELLS allele. b Western blot analysis of HELLS expression in Hells cKO (Chx10-Cre Hellslox/lox) and littermate control (Hellslox/lox) shows effective reduction of HELLS protein upon Cre recombination of floxed HELLS alleles. Actin was used as a loading control. Band intensities were quantified by densitometry and normalized to littermate control. c RT-qPCR analysis of retinal cell marker genes. The genes of the seven major retina cell types are proportionately expressed in EGFP+ cells from Hells cKO mice compared with cells from Cre-negative littermate controls. All data are mean ± SD normalized to control littermates (n = 5). d Representative images of P21 retina cross-sections from Hells cKO Z/EG and littermate control mice immunostained with chx10 (bipolar), pkc-alpha (bipolar), and recoverin (photoreceptors) antibodies (red). Retinae were double immunostained with anti-EGFP to capture areas of Chx10-Cre-mediated EGFP expression. Nuclei were counterstained with DAPI (blue). ONL outer nuclear layer, INL inner nuclear layer, GCL ganglion cell layer, ipl inner plexiform layer, opl outer plexiform layer. e Representative images of P21 retina dissociated cells from Hells cKO Z/EG mice immunostained with recoverin (photoreceptors), cone arrestin (cone photoreceptors), calbindin (horizontal and a subset of amacrine cells), chx10 (bipolar), and pkc-alpha (bipolar) antibodies (red). Cells were double immunostained with anti-EGFP to capture areas of Chx10-Cre-mediated EGFP expression. Nuclei were counterstained with DAPI (blue). f Quantification of the proportion of immunoreactive cells for each cellular marker antibody shown in E and Supplementary Fig. 3 was determined for EGFP+ and EGFP− cells from Hells cKO Z/EG mice from independent litters (n = 3). Each bar represents the mean ± SD of 500 cells scored from each retina. g, h ERGs were recorded from 5-week-old Hells cKO (red line) and littermate control (black line). a-wave amplitude (g) and b-wave amplitude (h) were recorded at various light intensities. All measurements are mean ± SD (n = 4).