a, Synthetic promoter design strategies. ATG is the translation start site. b, Workflow for AAV-based retinal cell-type targeting screen. c, Confocal images of sections of AAV-infected retinas. Left: CatCh-GFP (green); middle-left, immunostaining with fluorescent marker (magenta); middle-right: CatCh-GFP and marker; right: CatCh-GFP and marker and nuclear stain (Hoechst, white). d, Left: confocal images of AAV-infected retinas (top view), CatCh-GFP (black). Middle: quantification of CatCh-GFP+ cell density as a percentage of target cell-type or cell class density; values are the mean ± s.e.m. from n = 12 confocal images. Right: quantification of AAV-targeting specificity shown as a percentage of the major (black) and minor (gray) cell types or classes among cells expressing CatCh-GFP. ONL, outer nuclear layer; OPL, outer plexiform layer; INL, inner nuclear layer; GCL, ganglion cell layer.