Fig. 2. Proliferation of precursor cells in the CMZ. (A-C) Double staining for cdk2 expression (A) and BrdU uptake (B). BrdU was injected at stage 41. The embryos were fixed one hour later and then in situ hybridisation and BrdU immunostaining were performed. (C) Overlaid image. (D) Immunostaining of stage 41 CMZ with MPM-2 antibody. Mitotic cells with endfeet are indicated by arrows, and differentiated photoreceptors and RGCs close to CMZ are indicated by arrowheads. (E), Double staining of stage 41 CMZ using phosphohistone H3 antibody (red) and calbindin antibody (green) to identify cone photoreceptors. (F) Immunostaining with cyclin A2 antibody. (G) Immunostaining with cdc2 antibody. The end of the CMZ is indicated by a dashed line in C, D, E, F and G. (H), Schematic model of the expression of cell cycle components and determination genes in the CMZ of the stage 41 embryo.