Figure 2. Overexpression of alk promotes cell proliferation and affects neurogenesis.

(A,B) Confocal sections of HSE:cfp embryos. Sib (A) and Tg+ (B) embryos show no difference in number and distribution of pH 3 and HuC/D positive cells. (C) Y-axis indicates numbers of pH 3 positive cells counted in a 50 µm confocal stack of the hindbrain. Mean ± SEM, n = 10 embryos in each group. Sib and Tg+ HSE:cfp embryos were not significantly different (p = 0.84). Sib and Tg+ embryos of both alk:HSE:cfp lines were significantly different (***p<0.001). Unpaired two tailed t-test. (D–G) Confocal sections of alk:HSE:cfp ¹ embryos. Sib (D) and Tg+ (E–G, from three different embryos) had different neural tube shapes. Dividing cells (pH 3, green) and neurons (HuC/D, red) in Tg+ embryos (E–G) were mispositioned (arrowheads), with aberrant patterns. (E′) High magnification of the boxed area in (E). Asterisk labels 4^th ventricle. Arrows label small cavities found in the neural tube. (H,I) Confocal sections of alk:HSE:cfp ¹ embryos, with BrdU labelled cells in S-phase. In Sib (H), BrdU positive cells occupy a region between dividing cells and neurons that exited the cell cycle, in a pattern complementary to pH 3 and HuC/D in (A,B,D). In Tg+ (I), BrdU positive cells were randomly positioned. Smaller dimension of samples in (H,I) might be due to HCl treatment in the experiment procedure. (J,K) Manual sections of embryos after in situ hybridization showed expanded ccnd1 expressions in Tg+ (K) in comparison to Sib embryos (J). Sib, transgenic negative siblings. Tg+, transgenic positive embryos. All images are sections perpendicular to neural tube. Scale bars: 50 µm.