Figure 6

mPer2 mutation does not affect end-stage neurogenesis in the adult dentate gyrus because of a compensatory increase in apoptotic cell death. To assess the "long-term" neurogenesis, WT and Per2^Brdm1mice received a daily injection of BrdU (i.p. injection at 100 mg/kg of body weight) during 5 consecutive days and were sacrificed 3 weeks after the last injection. (A-C) «Z-stack» overlays on 40 μm-thick coronal sections of 5 adjacent confocal planes (step size = 1 μm) displaying the DG of P45 WT mice exposed to the "long-term" BrdU incorporation protocol and stained for BrdU (A), for NeuN (B), or both (C) (white arrow points towards a BrdU⁺/NeuN⁺ neuron). (D) Histograms representing the overall number of mature newborn BrdU⁺/NeuN⁺ neurons in the DG of WT and Per2^Brdm1mice (mean ± SD, n = 9 for WT mice and n = 6 for Per2^Brdm1, Student's t-test, p > 0,05). (F-G) Confocal images displaying TUNEL⁺ cells in the DG of P45 WT (F) and Per2^Brdm1mutant mice (G). TO-PRO^®-3 was used for nuclear counterstaining. (E) Total number of TUNEL⁺ cells (per 40 μm-thick DG section) displays a significant difference between WT and Per2^Brdm1mice (mean ± SD, n = 4, Student's t-test, *p < 0,05). (H-J) Newborn cell in the SGL of the DG expressing BrdU, (one i.p. injection of BrdU and sacrifice 4 days later i.e. "short-term" neurogenesis assay) is TUNEL⁺. Scale bar in A = 30 μm for A-C and H-J, 50 μm for E-F, ns = non significant.