FIGURE 4.

The Nbs1-CNS-Δ/Atm^−/− double mutant genotype reduces cell proliferation and increases cell death in the cerebellum. A, P5 cerebellar sections derived from the Nbs1-CNS-Δ//Atm^−/− and WT were immunoreacted with Ki67 (marker for cell proliferation). EGL, external granular layer; IGL, internal granular layer. B, quantification of Ki67-positive cells is shown. C, P10 cerebellar sections derived from the Nbs1-CNS-Δ//Atm^−/− and WT were immunoreacted with calbindin (marker of Purkinje neurons) active caspase 3 (marker for apoptosis). White arrows point at Purkinje neurons, which are active caspase 3-positive cells. D, quantification of active caspase 3-positive cells is shown. E, P10 cerebellar sections derived from the Nbs1-CNS-Δ//Atm^−/− and WT were stained with Fluoro-Jade (marker of degenerative process). F, dissociated glial cell cultures were prepared from 1–2-day-old mice of various Nbs1/Atm genotypes. Bar = 25 μm. G, identical numbers of cells were taken from 1 week cultures, re-plated, and counted after 5, 10, and 15 days. The experiments were performed in cultures from at least three mice for each genotype. Statistical analysis was performed using two-tailed Student's t test. Error bars represent S.E. Green asterisks show the statistical significance between Atm^−/− and Nbs1-CNS-Δ//Atm^−/−; pink asterisks show the statistical significance between Nbs1-CNS-Δ and Nbs1-CNS-Δ//Atm^−/−. *, p < 0.05; **, p < 0.02; ***, p < 0.01.