Forced Notch signaling does not affect commissural axons to cross the midline.
Double immunostaining for GFP and TAG1 was performed after electroporation of empty and NICD vectors. (A–C) In the control, GFP+ (A) and TAG1+ (B) axons cross the ventral midline normally. GFP/TAG1 double-labeled axons are observed at the floor plate (C, arrowheads in inset). (D–F) NICD mis-expression decreases the number of GFP+ axons in the midline (D) and TAG1+ axons in the electroporated side (E, arrow) compared with those in the control (arrow in B). Although GFP+ axons toward across the midline are greatly reduced in number, the remainders are still GFP/TAG1 double-positive (F, arrowheads in inset). Insets in (C) and (F) show the high magnification views of the boxed areas in their respective panels. Scale bars: 200 µm for (A, B, D, E); 100 µm for (C, F); 50 µm for the insets in (C, F). (G) Quantitation of the ventral areas spanned by TAG1+ axons in the rostral hindbrain. Compared to those on the contralateral (C.L.) side, the expression of NICD, VP16 or Hes1 decreases the area ratios of TAG1+ axons on the electroporated (E.P.) side. R218H or Hes5 expression does not affect TAG1+ axons. *, p<0.05.