Neurogenins are required for the normal number of basally dividing progenitor cells in the thalamus. (A-D) E12.5 frontal sections showing the expression of the mitosis marker PH3 in (A) control compound heterozygote (Neurog1-/-;Neurog2+/-), (B) Neurog1 single knockout (Neurog1+/-;Neurog2-/-), (C) Neurog2 single knockout (Neurog1+/-;Neurog2-/-) and (D) Neurog1/2 double knockout (Neurog1-/-;Neurog2-/-) embryos. (E) Cell count of PH3-positive cells in the pTH-C domain of the thalamus of neurogenin knockout mice (n = 9 for Neurog1+/-;Neurog2+/-, n = 13 for Neurog1-/-;Neurog2+/-, n = 13 for Neurog1+/-;Neurog2-/-, n = 4 for Neurog1-/-;Neurog2-/-). One sample is one section. Numbers of basal, apical and basal plus apical PH3-positive cells as well as the ratio of basal PH3+ cells/total PH3+ cells were compared between the genotypes. One-way ANOVA for Neurog1+/-;Neurog2+/-, Neurog1-/-;Neurog2+/-and Neurog1+/-;Neurog2-/- embryos; F = 11.96 for basal PH3, F = 1.744 for apical PH3, F = 4.517 for basal + apical PH3, F = 5.881 for basal/total ratio. N.s., not significant; **P < 0.01. (F-H) Expression of the pTH-R/prethalamic marker Ascl1 in neurogenin knockout mice at E12.5. Note induced expression of Ascl1 in the pTH-C domain in (G,H). (I-L) Expression of transcription factor Tbr2 in Neurog1/2 double knockout embryos at E12.5. Panels (I,J) show reduced but still persistent expression of Tbr2 in the neocortex of Neurog1/2 double knockout mice. (K,L) Induction of Tbr2 in the thalamic mantle zone of Neurog1/2 double knockout mice. Olig3 is used as a reference for the thalamic VZ and SVZ. Scale bar: 100 μm for (A-D,F-L).