Fig. 4. A significant decrease in the diameter of mutant neurospheres is caused by a concomitant increase in cell death and a decrease in cell proliferation of nestin-positive progenitors. (A) The number of both mutant and control neurospheres was determined for each individual diameter ranging from 10 to 90 µm. The percentage of small (10-30 µm) neurospheres present in the mutant populations is significantly elevated in relation to control populations. In parallel, the mean percentage (±s.d.) of larger spheres (40-70 µm) is significantly reduced in ß1 integrin-deficient neurospheres compared with the value in controls (n=4; *P<0.05; **P<0.01; ANOVA). (B) The cellular composition of mutant neurospheres is different from control populations. In mutant neurospheres, the percentages of both GFAP-positive astrocytes and ß III-tubulin-positive neurons are increased whereas the number of nestin-positive progenitors is reduced. (C) The percentage of proliferating cells, stained with an antibody against phosphorylated histone H3, is significantly decreased in mutant neurospheres. (D) The number of apoptotic, TUNEL-positive cells is significantly increased in mutant neurospheres. (E) The percentage of apoptotic nestin-positive progenitors is significantly increased in the mutant neurospheres. Mean percentages±s.d. are shown for three separate experiments (D-E); *P<0.05, ***P<0.001 compared with respective values in control neurospheres (B-E).