Fig. 3.

Widespread Crx>Math5 expression has little effect on cell fate decisions in the retina. (A–F) Sections from adult Crx>Math5-IRES-Cre BAC (shortened as Crx>Math5 BAC) or matched Crx>Cre BAC control transgenic mice carrying R26floxGFP reporters were coimmunostained with GFP and informative markers. GFP and marker costaining (bottom) and GFP alone (top) are indicated (arrows). Müller glia were identified by Sox9 (A,B), amacrines by AP2α (C,D) and horizontal neurons by calbindin (E,F). Arrowheads in E and F mark calbindin+ horizontal cells that are GFP−. (G–H) Flatmounts of adult Crx>Math5 BAC and Crx>Cre BAC retinas labeled with retrograde rhodamine dextran and imaged through the GCL. Some lineage-marked (GFP+) rhodamine dextran (rhod dext) [+] RGCs (arrows) and rhod dext [−] displaced amacrine cells (arrowheads) are indicated (insets). While both transgenes mark essentially all photoreceptors and bipolar cells (Suppl Fig. 2), a small fraction of other cell types was also labeled in each case. The fate spectra are similar, with or without Math5. Rare horizontal cells were labeled in Crx>Math5 BAC Tg mice, but not in Crx>Cre BAC Tg controls, most likely due to differences in transgene expression level. Scale bar, 50 µm.