ATBF1 regulates apoptosis in primary cortical neurons in the presence of Aβ1-42-induced neurotoxicity. A, primary cortical neurons were seeded at a density of 1 × 106 cells/ml in poly-d-lysine-coated 24-well glass plates. Three days after plating, the cells were transfected with ATBF1 siRNA-1 or control siRNA for 48 h. After transfection, the cells were then incubated with 0, 2.5, or 10 μM Aβ1-42 for 16 h, and apoptosis was analyzed by TUNEL assay. Cell nuclei were also stained with DAPI. Left panel: Representative images showing DAPI-stained and TUNEL-positive cells. Right panel: quantification of TUNEL. TUNEL-positive neurons were counted from at least 400 neurons from five randomly selected fields in three independent experiments. B, primary cortical neurons were seeded at a density of 1 × 106 cells/ml in poly-d-lysine-coated 96-well plates. Three days after plating, cells were transfected with ATBF1 siRNA-1 or control siRNA for 48 h, and the cells were then treated with 0, 2.5, or 5 μM Aβ1-42 for 16 h. Caspase-3/7 activity was determined using a Caspase-Glo™ 3/7 assay kit. All the values are presented as the mean ± SEM of three independent experiments. *p < 0.05, **p < 0.01 vs control siRNA. N.S., not significant, as determined by one-way ANOVA followed by Duncan's test.