Fig. 5. Absence of Ngn2 causes a reduction of the MZ and retention of cells within the VZ/IZ. (A-D,F-I) ß-III-tubulin staining at E13.5 revealed the presence of neurons within the MZ of the mesDA domain despite the almost complete lack of Th-positive neurons. (E,J) However, DAPI staining showed a reduction in total cell number in the MZ and an accumulation of retained cells in the VZ/IZ of the Ngn2 mutants in comparison to heterozygous mice. Diagrams on the right show the positioning of the VZ, IZ and MZ in the heterozygous and mutant mice.