Fig. 5. Ptf1a lineage-labeled cells are transfated to RGCs in Ptf1a-deficient embryos. (A-F) An anti-GFP antibody was used to detect YFP in E18.5 Ptf1a^Cre;R26R-EYFP retinas and an anti-Brn3b antibody was used to detect differentiated ganglion cells. YFP acts as a lineage marker for cells that have expressed the Ptf1a locus. YFP (green) does not co-localize with Brn3b (red) in the presence of Ptf1a, but they do co-localize in Ptf1a-null embryos (compare E with F). (G-L) An anti-GFP antibody was used to detect citrine, a modified version of GFP, in E18.5 Ptf1a^Citrine embryos. Citrine serves as a lineage marker for cells that are expressing or have expressed the Ptf1a locus during the past couple of days. Citrine (green) does not co-localize with Brn3b (red) in the presence of Ptf1a, but they do co-localize in Ptf1a-null embryos (compare K with L). Arrows in F indicate Brn3b⁺YFP^- `newly specified RGCs' in the onbl. Arrows in L indicate Brn3b⁺citrine⁺ Ptf1a lineage-labeled RGCs. Scale bar: 50 µm. Abbreviations: onbl, outer neuroblastic layer; INL, inner nuclear layer; GCL, ganglion cell layer.