library_construction_protocol: Four retinas isolated from wildtype mouse embryos at E16.5 were pooled, and then dissociated using papain dissociation system (#LK003150, Worthington Biochemical Corporation, Lakewood, NJ). The CUT&Tag library was prepared using CUT&TAG-IT Assay Kit (#53160, Active Motif, Carlsbad, CA) following manufacturer's protocols.