Fig. 3

Zic1 and Zic4 function is required after initial ventricle opening for dorsal neural proliferation in the hindbrain. (A, B) Comparison of the quantitative analysis of hindbrain mitotic index at 18 hpf (A) and 24 hpf (B) in controls, Zic1 morphants, Zic4 morphants, and Zic1 + 4 morphants. Mitotic index was calculated in controls and Zic morphants as the ratio of the number of proliferating cells over the total number of cells (as described in Materials and methods). Dorsal neural proliferation at 18 hpf remained unaffected in Zic morphants compared to controls (A), while at 24 hpf the mitotic index was reduced in Zic morphants compared to controls (B). n is the number of embryos assessed per experimental condition. Asterisks in panel B indicate significant differences compared to controls. (C, D) Dorsal confocal sections (3 μm thick; longitudinal view) through hindbrain immunolabeled with the proliferating marker pH3 (C, D), counterstained with the nuclear marker Sytox green (C′, D′), and merged (C″, D″) of 24 hpf controls (C, C′, C″) and Zic1 + 4 morphants (D, D′, D″).