Figure 1.
Prenatal deletion of Dnmt1 impairs cell proliferation and neurogenesis in the adult brain. (A) Diagram of the Dnmt1 conditional knockout strategy in NSCs. Dnmt1flox/flox mice were crossed with Nestin-CreERT2 mice, yielding progeny in which tamoxifen administration results in the deletion of Dnmt1 (exons 4 and 5) in Nestin-expressing NSCs. (B) Experimental scheme for assessing the effect of Dnmt1 deletion on cortical development and neurogenesis. Pregnant mice were injected with tamoxifen (2 mg) at E15 to induce deletion of Dnmt1 in NSCs, and the brains of the offspring were analyzed at 8-week old. (C) Representative immunofluorescence images of DCX (red) in sagittal adult (8-week old) brain sections from control and cKO mice. White open rectangles indicating the RMS and DG are shown in higher magnification images, respectively. (D) DCX immunostaining images (white) of representative newborn neurons in the DG of control and cKO mice. (E) DCX immunostaining images (red) of representative SVZ neurons in coronal adult brain sections from control and cKO mice. White open rectangles in the left panel images are shown in higher magnification in the right images. (F) DCX+ cells in (E) were quantified along the lateral wall of the lateral ventricle (mm) (Control = 3, cKO = 3). (G) Ki67 immunostaining (green) images of representative SVZ neurons in coronal adult brain sections from control and cKO mice. The nucleus was stained with Hoechst (Blue). (H) Ki67+ cells in (G) were quantified along the lateral wall of the lateral ventricle (mm) (Control = 3, cKO = 3). Scale bars are indicated in each figure. Values represent mean ± SEM; *P < 0.05, ***P < 0.001. Student's t-test. NSC: neuronal stem cells; Dnmt1: DNA methyltransferase 1; DCX: doublecortin; RMS: rostral migratory stream; DG: dentate gyrus; SVZ: subventricular zone.