Pax6 mutant mice show regionally specific mis-expression of Ascl1 and reduction of Neurog2 expression in the thalamus, which is accompanied by reduced basally dividing cells. E12.5 frontal sections showing double immunostaining of Neurog2 (A,C,E,G) or Ascl1 (B,D,F,H) with PH3 in Pax6 mutant embryos (C,D,G,H) and their littermate control (A,B,E,F). (A-D) Sections at the dorsal level show a largely normal level of Neurog2 expression in the pTH-C domain of the thalamus (A,C) and the absence of Ascl1 expression (B,D). Basal PH3-positive cells also appear normal (B,D, arrows). (E-H) In more ventral sections, however, Neurog2 expression is reduced (E,G) and Ascl1 is ectopically expressed (F,H). In the region where Ascl1 is induced, basal PH3-positive cells appear to be reduced (F,H, arrows). (I,J) Cell count of PH3-positive cells in the pTH-C domain of the thalamus of Pax6 knockout mice (n = 14 for each dorsal section, n = 14 for ventral sections). One sample is one section. (I) The ratio of basal PH3+ cells/total PH3+ cells was compared between control dorsal, Pax6 knockout dorsal, control ventral, and Pax6 knockout ventral sections. One-way ANOVA was done to compare; F = 56.25. (J) The numbers of apical and basal PH3-positive cells on ventral sections were compared between the Pax6 knockout and the control wild-type embryos. Student's t-test was done. ***P < 0.001. Error bars are standard error of he mean (SEM). Scale bar: 100 μm for (A-H).