Fig. 6

Proliferation is reduced in cells with active Wnt/β-catenin signaling. A: In 48 hours postfertilization (hpf) wild-type eyes, cyclinD1 is expressed in the sox2 and atoh7 domain but is excluded from the most peripheral cells. B: myca is expressed in the sox2 domain and is also excluded from the most peripheral cells. C,D: In 48 hpf apc eyes, cyclinD1 and myca are excluded from the expanded Wnt/β-catenin activation domain but are expressed in the central retina. E: In 50 hpf bromodeoxyuridine (BrdU) -treated wild-type embryos chased for 1 hr, BrdU is incorporated in cells of the sox2, atoh7, and cyclinD domain. Cells peripheral to these zones are mostly devoid of BrdU labeled cells (arrow heads). F: In 50 hpf apc mutant eyes, the expanded peripheral zone is BrdU-negative suggest that cells in the Wnt/β-catenin pathway domain are postmitotic or slowly cycling (outlined by arrowheads). G: In 50 hpf BrdU treated wild-type embryos chased for 2 hr, most cells in the periphery of the eye incorporated BrdU, suggesting that they are more slowly cycling than central cells. However, a few very peripheral cells are still BrdU negative. The very bright cells in the periphery are macrophages and not part of the developing retina. H: In 50 hpf apc mutant eyes that have been treated with BrdU and chased for 2 hr, BrdU is incorporated in single cells in 35% of all sections counted (n = 31; white arrowhead); demonstrating that not all cells are postmitotic.