Smad3 deficiency leads to apoptotic cell death and fewer intermediate progenitor cells. (A) The total number of BrdU-ir cells 30 minutes, 8 hours and 24 hours after delivering the BrdU pulse (150 mg/Kg: **, P ≤ 0.01, two-way ANOVA, Holm-Sidak post hoc test n = 3-5 mice per genotype). (B) Histograms showing the total number of activated caspase 3-ir cells and those double-labeled with BrdU in the DG (*, P ≤ 0.05, **, P ≤ 0.01, Student t-test, n = 3 mice per genotype). (C) Confocal images of activated caspase 3/BrdU double-labeling, 24 hours after BrdU injection showing apoptotic BrdU-ir cells in the DG. Scale bar 10 μm. (D) Confocal image showing nuclear activated caspase 3 in intermediate progenitor cells expressing Mash1 in the cytoplasm. Cell shrinkage morphology, nuclear condensation and fragmentation and activated caspase 3 are suggestive of apoptosis. Scale bar 10 μm. (E-F) Quantification of the number of Mash1(+) cells in the DG along the rostro-caudal axis showed that Smad3+/+ mice had fewer intermediate progenitor cells (**, P ≤ 0.01, Student t-test, n = 6 per genotype).