Fig. 6. Deficiency in neurogenesis in Mash1 and Ngn2 mutants. (Aa-Dc) Generation of motoneurons and Islet1⁺/Olig2⁺ neurons at E12.5. Circles in Aa-Da indicate the cluster of motoneurons in the ventral MZ. Arrowheads in Ca and Cc indicate ectopic HB9⁺ cells in and adjacent to the VZ in Mash1^{KI Ngn2/+} mice. Thick arrows in Aa-Da indicate the locations of the areas magnified in Ab-Db. (E,F) The numbers of HB9⁺ and Islet1⁺ cells per section in the motoneuron cluster in the ventral MZ (E) and in the area close to the p^* VZ (F) in the wild-type and various mutant mice. (G) The number of Islet1⁺/Olig2⁺ cells in the lateral MZ. (H) Schematic diagrams summarizing the defects in neurogenesis and oligodendrogenesis in the Olig2⁺ domain in various mutants. Ngn2⁺ cells and neurons are shown in red, whereas Mash1⁺ cells and oligodendrocytes are in blue. Cross marks and thick circles indicate a decrease or absence, and increase, respectively, of specific cell populations in the mutants. Scale bars: in Da, 100 µm for Aa-Da; in Dc, 50 µm for Ab-Db,Ac-Dc.