Fig. 2. Cells in the CB/CMZ are a source of regenerating retina. (A) Collagen type IX immunohistochemistry performed on an E4 operated eye 4 hours post-retinectomy shows the CB/CMZ region has not been removed. (B) An adjacent section shows that the CB/CMZ is rich in cells that express Pax6 (blue) and Chx10 (red). White arrowheads indicate progenitor cells that co-express Pax6 and Chx10. (C) Another adjacent section shows that within 4 hours of retinectomy, most cells in the CB/CMZ are proliferating and labeled with BrdU, suggesting that progenitor cells (like those shown in B) are proliferating. (D) The CB/CMZ was labeled with DiI (red) immediately after retinectomy. The collagen type IX (green) immunofluorescence confirms that the labeled region is the CB/CMZ. (E) At E5, 1 day after the CB/CMZ was labeled, DiI-labeled cells have migrated from the CB/CMZ and generated a neuroepithelium. (F) Three days after retinectomy this phenomenon is still apparent. The asterisk indicates the region where the CB/CMZ was originally labeled with DiI. c, cornea; CB/CMZ, ciliary body/ciliary marginal zone; l, lens; RPE, retina pigmented epithelium; pe, pigmented epithelium; cr, retina that regenerated from the CB/CMZ. The red arrowheads indicate the site at which the incision was made during the retinectomy. Scale bar in A is for A-C.