Fig. 4

Maintenance of the photoreceptor mosaic in tbx2b^p25bbtl mutant adults. Transverse (A and C) and tangential (B and D) histological sections through the ONL from WT and tbx2b^p25bbtl adult animals (rods are GFP⁺) (green), immunolabeled for UV opsin (red), and counterstained with DAPI (blue). (A and C) Tiering of the rod and cone photoreceptor cells is maintained although the UV cones (asterisks) in the tbx2b^p25bbtl retinas are diminished in number and appear to have a greater width than in WT retinas. The approximate plane of the sections in (B) and (D) are indicated [arrows in (A) and (C)]. (B) Immunolabeling of tangential sections for the UV opsin reveals the photoreceptor cell mosaic composed of rows of UV cones and blue cones (arrowheads). (D) In tbx2b^p25bbtl the regular arrangement of the rows of blue cones (gaps in labeling; arrowheads) and occasional UV cones are maintained although the width of the cones is greater and there is some distortion of the row mosaic.