Generation of Dgcr8^+/− mice. A, Expression of DGCR8 in the mouse dentate gyrus. Brain sections were stained with anti-DGCR8 antibody (green). The nuclei were stained with DAPI (blue). B, Representative images of double immunostaining of anti-DGCR8 (green) with anti-Ki67, anti-Calretinin, anti-NeuN, or anti-GFAP antibodies (red) in the mouse dentate gyrus. The nuclei were stained with DAPI (blue). C, Schematic diagram of the genomic structure of Dgcr8 and intronic gene-trap insertion between exons (Ex) 8 and 9. Black arrowhead indicates approximate genomic location of PCR primers used for genotyping. D, Targeted allele was verified by PCR genotyping. Genomic DNA samples extracted from tail snips of Dgcr8^+/− and Dgcr8^+/+ mice were genotyped using the primers shown in C. E, qRT-PCR analysis confirming reduction in wild-type Dgcr8 mRNA in 2-month-old mouse hippocampus (**p < 0.05, Dgcr8 vs control, two-tailed t test, n = 4, mean ± SEM). F, Western blotting analysis. Top shows a reduced amount of the 120 kDa wild-type DGCR8 (bottom arrowhead) protein and production of the expected 220 kDa chimeric protein (top arrowhead) in the Dgcr8^+/− mouse brain, and bottom shows a similar amount of Actin protein. G, miRNA expression profiling in male Dgcr8^+/− mouse hippocampus. Hierarchically clustered heat map representing differences in miRNA expression in Dgcr8^+/− mouse hippocampus. Relative levels of expression are colored from green (low) to red (high). H, qRT-PCR analysis of 11 mature miRNAs in the hippocampus of 2-month-old Dgcr8^+/− mice (*p < 0.05, **p < 0.01, Dgcr8^+/− vs Dgcr8^+/+, two-tailed t test, n = 4, mean ± SEM).