Fig. 5.

Inhibition of Ngn2 activity in a subpopulation of the cortical progenitors in Sey/Sey.Coronal sections from E16.5 wild-type (A, B) andSey/Sey (A′, B′) brain hybridized with Ngn2 (A,A′) and Pax6 (B,B′) probes. In A note that the region of the VP in the VZ of the LGE is still distinguishable at this late developmental stage. In the mutant, the expression ofNgn2 is completely abolished from the region of the VP and LP, severely repressed in the DP, but appears unaffected in the MP. In B′ note that the enlarged VZ–SVZ in theSey/Sey pallium is expressing abundantly the mutantPax6 mRNA (B′). C, D,Coronal sections from E13.5 WT brain were double-labeled by in situ histochemistry with the Ngn2 antisense RNA probe (blue cytoplasmic staining) and by immunohistochemistry with the Pax6 antibody (red nuclear stain). The enlarged inserts are higher magnifications showing that some Pax6-immunoreactive cortical progenitors expressNgn2 mRNA (open arrowheads). Thefilled arrowheads point to progenitors that are onlyNgn2+. D is a composite picture ofC and the Pax6 immunostaining; the overlay has been done in Adobe Photoshop.