Association of SMN and p53 in fibroblasts. (A) Control and SMA fibroblasts were left untreated or treated with 25 μM camptothecin for 8 h. Camptothecin-treated cells were fixed and stained with anti-p53 (mouse) and anti-SMN (rabbit) antibodies. Secondary antibodies were either labeled with Alexa 555 (anti-mouse, in red) or FITC (anti-rabbit, in green). Images of p53 and SMN were taken by confocal microscope (63×). Phase contrast images (DIC) for the immunostained cells are included. Scale bar is 10 μm. Gems are indicated by arrows. (B) Representative orthogonal views from z-stacking images of untreated control fibroblasts in (A) are shown here. The arrows indicate co-localization between SMN and p53. SMN = survival motor neuron, CPT = camptothecin, and DIC = differential interference contrast.