Fig. 2. Hes1 expression in the spinal cord. (A-C) Double immunostaining of Hes1 and Ki67 at E10.5. Hes1-expressing cells in non-boundary regions are mostly positive for Ki67 (C, bracket). In contrast, Hes1-expressing cells in the roof plate and the floor plate are negative for Ki67 (C, arrowheads). (D-G) BrdU uptake in the spinal cord at E11.5. BrdU-positive cells are present in non-boundary regions but very rare in the roof plate (E, upper box, and F) or the floor plate (E, lower box, and G). Boxed regions in E are enlarged in F and G. (H-J) Hes1 protein expression in the roof plate at E10.5. Inset in H shows Wnt1 expression in the roof plate. (K-M) Hes1 protein expression in non-boundary regions at E10.5. (N-P) Hes1 protein expression in the ventral spinal cord including the floor plate at E10.5. Inset in N shows Shh expression in the floor plate. In non-boundary regions just dorsal to the floor plate, Hes1 protein is expressed at variable levels (P, bracket). (Q) Hes1 protein expression (top). (Bottom) Relative intensity of Hes1 signal was measured (see Materials and methods): error bars represent s.e.m. (a total of 108 roof plate cells, 109 floor plate cells and 1,106 non-boundary cells in six different sections were examined). Scale bars: 100 µm (C-E), 50 µm (F, G and P).