Fig. 2

ALT activation in FRDA fibroblasts. a Percentage of the PML bodies associated with telomeres demonstrate high co-localisation in all FRDA cells, GM03665, GM03816 and GM04078, compared to GM07492 and HeLa controls. 99 % of the telomere foci co-localised with the PML bodies in U2OS ALT-positive control cells, n = 50. b Representation of APBs detected by immuno-FISH in FRDA and control (normal) fibroblast cells, U2OS ALT-positive control cells (+Ctrl) and HeLa ALT-negative control cells (−Ctrl). Interphase cells were stained with anti-PML (green) and telomeric Cy3-labeled PNA probes (red). Nuclei were counterstained with DAPI. Scale bar = 10 μm. White arrowhead indicates an APB in a FRDA cell. c T-SCE analysis of human FRDA cells by CO-FISH showed a significant increase (P < 0.001) in T-SCE levels of FRDA cells compared to the controls, n = 20–50. d Representative CO-FISH results, showing T-SCEs events (indicated by arrowheads) in FRDA and control (normal) fibroblasts, U2OS ALT-positive controls (+Ctrl) and HeLa ALT-negative controls (−Ctrl). Graph data are shown as mean ± SEM (^*** P < 0.001, evaluated by Student’s t test). All the experiments were repeated independently, at least twice