Figure 6

Blocking Wnt signaling with XAV939 leads to loss of the progenitor population in the CMZ. Zebrafish at 3 dpf were given a pulse of BrdU to mark dividing cells, then exposed to either 0.15% DMSO as a vehicle control or 15 μM XAV939 for 2 days and fixed for analysis at 5 dpf. In control fish at 5 dpf, the progeny of cells labeled with BrdU at 3 dpf had differentiated and were displaced out of the CMZ and a population of dividing cells that express PCNA remain in the CMZ (bracket) at 5 dpf (A). In fish treated with 15 μM XAV939, the progeny of the cells labeled with BrdU at 3 dpf remain at the retinal margin and there are no PCNA-labeled cells (B). Overlays in A and B are shown including a brightfield image to allow visualization of the RPE marking the edge of the retina. Labeling control (C, E) or XAV939-treated (D, F) fish with antibodies against Pax6 (C, D) or Sox2 (E, F), shows that XAV939 greatly reduces the number of cells expressing these progenitor cell markers (dotted line marks the extent of labeling in the CMZ). Scale bar = 20 μm.