For best reproduction and clarity of SAC arbors, maximized projections of confocal images were inverted and contrast-enhanced using Photoshop (Adobe Systems Inc.). For morphometric analysis of SACs, we used Fiji software and selected confocal image series of wild-type and Pcdhg mutant SACs situated in comparable retinal eccentricities. Self-crossings per dendritic branch order were quantified as number of branch overlaps detected in single confocal planes; crossings occurring distal to 5′ branch order could not be quantified accurately due to severity of defects in mutants. Dendritic field diameter was measured as the longest axis of arbor. In some cases, arbors were reimaged by oversampling using a 60X 1.45NA objective at x,y,z resolution of 47 × 47 × 131and then subjected to deconvolution using Huygens software (http://www.svi.nl/HuygensProfessional).
