Fig. 3. Effect of targeted Ptf1a deletion on the formation of different retinal cell types. (A-P) Retinal explants were prepared from wild-type (A,C,E,G,I,K,M,O) and Ptf1a^Cre/Cre (B,D,F,H,J,L,N,P) embryos at 18.5 and then cultured for 2 weeks. The neuronal subtypes were examined by immunohistochemistry (red) for rhodopsin (rods; A,B), Chx10 (bipolar cells; C,D), calbindin (horizontal and amacrine cells; E,F), syntaxin (horizontal and amacrine cells; G,H), calretinin (amacrine cells and RGCs; I,J), GABA (GABAergic amacrine cells; K,L), tyrosine hydroxylase (Th, dopaminergic amacrine cells; M,N) and Cralbp (RPE and Müller glia; O,P). In retinal explants, there is postnatal degeneration of pre-existing RGCs, owing to RGC axon severance resulting from optic nerve transection during tissue preparation. During explant culture, folding of retinal tissue usually results in mirror-image-like duplication on the periphery (broken lines in L and P). Arrowheads in L,P indicate rosette-like structure formation. Scale bars: 25 µm. Abbreviations: ONL, outer nuclear layer; OPL, outer plexiform layer; INL, inner nuclear layer; GCL, ganglion cell layer; IPL, inner plexiform layer.