Fig. 1. Colocalization of Mash1 and Ngn2 in the ventricular zone of the dorsal neural tube. E10.5 embryo transverse sections were processed for mRNA in situ hybridization (A) or immunofluorescence (B-F). (A) Pseudocolored overlay of adjacent sections hybridized with antisense Mash1 (pink) or Ngn2 (purple) probes to illustrate expression in the dorsoventral axis and possible overlap. (B) Double-label immunofluorescence shows Mash1 (red) and Ngn2 (green) in ventricular zone cells in the dorsal neural tube (region shown by bracket in A; ventricular zone is at the left in each panel). Arrows indicate Mash1 and Ngn2 co-expressing cells (yellow). (C-F) Co-labeling with BrdU incorporation was performed to detect cells in S phase. (C,E) Mash1 (red) cells incorporate BrdU (green) (detected as yellow, arrows). (D,F) Ngn2 (red) cells rarely score positive for BrdU incorporation (green). (E,F) Higher magnification images of the regions boxed in C,D. Scale bars: 90 µm in A; 25 µm in B-D; 15 µm in E,F.