Fig. 3 . Loss of PSA-NCAM reduces survival of cultured SVZ-derived neurons under basal conditions and in response to neurotrophins. (A) Epifluorescence images illustrating apoptotic cells in SVZ-derived cultures co-labeled for activated caspase 3 (red) and TUNEL (green). ßIII-tubulin staining (blue) was used to confirm the neuronal phenotype of cultured cells. (B) Quantification of cell death rate in the presence or absence of PSA-NCAM. When WT cultures are treated with Endo-N (PSA^- NCAM⁺) for 20 hours, or with a PSA-blocking antibody (mAb 735), a significant increase in death rate is found. ^*, P<0.05 (ANOVA, Holm-Sidak test). (C) Survival of WT cells is promoted by exogenous application of BDNF (100 ng/ml), but not of NGF. By contrast, cells lacking either PSA (WT+EndoN) or PSA and NCAM (NCAM^-/-) exhibit an enhanced cell death rate in response to NGF (50 ng/ml) and BDNF (100 ng/ml), as compared with WT neurons. ^*, P<0.05 (ANOVA, Holm-Sidak test).