Fig. 4

RA is required prior to 19 hpf for HSC formation.

Shown are representative flat-mount embryos following in situ hybridization analyses of cmyb gene expression in wild type (WT; A, D) or aldh1a2-morphant (B, C, E, F) 32 hpf embryos treated with DMSO (A, B) or 1 nM RA (C-F) at indicated time points. Lateral view of gene expression in the dorsal aorta region of the trunk is shown with anterior to the left. Compared to WT embryos (A), embryos treated with 1 nM RA (D) exhibit normal cmyb expression (two-tailed P = 1.000). aldh1a2-morphants (B) exhibit nearly abolished cmyb expression compared to WT embryos (two-tailed P = 0.01). cmyb expression is significantly restored in aldh1a2-morphant embryos treated with 1 nM RA at 4 hpf (C; two-tailed P = 1.000 compared to WT). cmyb expression is not significantly restored in aldh1a2-morphants treated with 1 nM RA at 19 hpf (E; two-tailed P < 0.0005) or 24 hpf (F; two-tailed P < 0.0005). See text for statistical tests.