Survival rate of newborn dentate granule cells decreases over the first 4 weeks.

<p>(A, B) Newly born DGCs labeled with the mitosis marker BrdU (cyan) frequently displayed DCX-expression (magenta) at 7 days post BrdU injection (7 dpi; A), while there was no co-localization of BrdU and DCX at 77 dpi (B). All of the counted BrdU+ cells were Prox1+ (green; A, B). Arrows in (A) point to BrdU/DCX/Prox1+ cells. Arrowheads in (B) point to a BrdU/Thy1-GFP+ cell. Due to their intense somato-dendritic labeling, Thy1-GFP+ cells could be easily distinguished from the green nuclear Prox1 immunostaining. (C) Quantification of BrdU/Prox1+ cells revealed a decline in survival of newborn DGCs between 7 and 35 dpi, whereas the total number of BrdU+ cells did not change between 35 and 77 dpi. Compared to the first week post BrdU injection, 14% of BrdU/Prox1+ cells were retained at 35 dpi, after which there was no further cell loss. (D) The number of BrdU/Prox1+ DGCs that expressed DCX also decreased between 7 and 35 dpi. No DCX/BrdU/Prox1+ cells could be detected between 35 and 77 dpi. All analyses were performed in the suprapyramidal blade of the right dorsal dentate gyrus (n = 3 animals for each group, 3 sections per animal). Error bars represent SEM. Scale bars in (A, B): 10 μm. GCL, granule cell layer; SGZ, subgranular zone.