Fig. 3. p53 negatively regulates neural stem cell proliferation, survival and self-renewal. Neurospheres from the lateral ventricle wall of adult p53-null mice grow faster and become larger compared with wild-type neurospheres. (A,B) Secondary neurospheres 6 days after passage. (C) Average volume of these neurospheres. (D) When neurospheres are dissociated, a larger proportion of p53^-/- compared with wild-type cells are capable of forming new neurospheres, demonstrating an increased self-renewal capacity. (E,F) Apoptotic cell death, indicated by Annexin V (E) or caspase activity (F) detected by flow cytometry, is decreased in the absence of p53. (G-I) A similar proportion of neurospheres from p53 mutant and wild-type mice are tripotent and form neurons (ßIII-tubulin+), astrocytes (Gfap+) and oligodendrocytes (O4+) upon differentiation. (J,K) BrdU incorporation is increased in p53^-/- neurosphere cells compared with cells from wild-type mice (K) and more cells from p53^-/- mice have a DNA content corresponding to S and M phases (J). There is no size difference between wild-type and p53 mutant cells (L). All bars in graphs indicate mean±s.d. ^*P<0.05, ^**P<0.01, ^***P<0.001. Scale bar: 100 µm.