Biocytin tracing and coupling in the SGZ of transgenic hGFAP-EGFP mice. (A1–A3) Confocal images of a coupled RG-like cell (p9–p12). (A1) Tracer spread from the recorded cell (asterisk) to 2 neighbouring cells (°). (A2) EGFP expression in the same section. (A3) Merged image. (B1–B3) Another example of a coupled RG-like cell (p90–p120). (B1) Biocytin spread from the recorded cell (asterisk) to 2 neighboring cells (°). (B2) EGFP expression. (B3) Merged image. (C1–C3) Confocal images of a noncoupled RG-like cell (p9–p12). (C1) Biocytin was confined to the recorded cell (asterisk). (C2) EGFP expression. (C3) Merged image. Cells were filled with biocytin during recording (20 min). Insets give the current profiles of the recorded cells (+20 to –160 mV; V_h = −70 mV). Broken lines indicate the border between SGZ and GCL. (Scale bar, 50 μm.)

Reduced proliferation and cell numbers in the DG of dko mice (p60). Confocal images of the DG of a dko (A1, B1, C, E) and a C57BL/6 mouse (A2, B2, D, F). Note that the coronal slices represent approximately the same z-position in rostrocaudal extension of the hippocampus, respectively. (A1, A2) Ki67 (red) and NeuN (green) immunostaining. (B1, B2) Ki67 staining (positive cells are framed) in gray scale of the same section as in (A1, A2) indicates lower proliferative activity in the dko mouse (for quantification, see Table S2). (C, D) Prox1 staining of coronal sections. Reduced numbers of Prox1-positive cells were observed in the dko mouse (C) vs. control (D). Frames in (D) indicate counting boxes. (E and F) BLBP staining, dotted lines indicate position of the GCL. (Scale bars, 100 μm.)

Ablation of connexins in RG-like cells decreases proliferation and neurogenesis in the adult DG. (A) Scheme depicting the Cre-expressing retroviral vector used. CRE, coding region of the Cre recombinase; LTR, long terminal repeat; arrow, transcription start site; Ψ, packaging signal. (B) Efficiency of Cre-mediated recombination after retroviral delivery in cultured cells. (Top) wildtype (wt); (Bottom) PCLMFGCre-infected CV1–5B cells. (Scale bar, 100 μm.) (C) Time schedule for Cre retrovirus application and subsequent analysis. (D) Histogram comparing the relative effects of inducible Cre retrovirus-mediated vs. constitutive ablation of connexins in Cx30^–/–/Cx43^fl/fl mice on numbers of Prox1- and Ki67-positive cells. Asterisks mark significant differences between ipsi- and contralateral side (virus injection; Cx30^–/–/Cx43^fl/fl mice) or dko and C57BL/6 mice (juvenile and adult, respectively).

Decreased BrdU incorporation and neurogenesis in the DG of dko mice (p60). (A) Peroxidase based immunohistochemical BrdU-detection revealed significantly lower numbers of labeled cells (arrowheads) in dko (A2) vs. control mice (A1). Representative images were obtained from 40-μm thick coronal sections through the hippocampus 2 h after the last BrdU injection. (Scale bar, 250 μm.) (B) Quantification of BrdU-positive cells in the SGZ in the rostrocaudal extension. Bar graphs illustrate the number of BrdU-positive cells per DG of dko (red) and control mice (blue), 2 h and 4 weeks after the last BrdU injection. At both time points significant reduction of BrdU labeling was detected. (C) Confocal images of a cell expressing BrdU (C2), Dcx (C3), and Prox1 (C4), taken 4 weeks after the last BrdU injection. (C1) Merged image. (Scale bar, 20 μm.) (D) Percentage of BrdU-positive cells expressing Prox1 only, or Prox1 and Dcx 4 weeks after the last BrdU injection. Note that almost all BrdU-positive cells adopted a neuronal phenotype, and that the proportion of Prox1-positive/Dcx-positive cells (black) did not differ between dko and control mice. In dko mice 0 to 4%, of the BrdU-positive cells expressed neither Prox1 nor Dcx (Left bar, open).