Fig. 1

DSB repair kinetics and nuclear morphology of normal and HGPS fibroblasts. a 53BP1 foci formation and clearance of 1-Gy irradiated normal cells (MJ90 and IMR90) and HGPS cells (AG11513 and AG11498). b The number of unrepairable 53BP1 foci persisting 1 month after 6 or 12 Gy irradiation in normal (MJ90) and HGPS (AG11513) cells. Insert photos are typical deformed nucleus and its 53BP1 foci from 12 Gy-irradiated and 1 month incubated (12-Gy/1-month) HGPS cells. c Calculation of the degree of nuclear dysmorphology. Exact area of a nucleus shown in upper left was measured as the area surrounded by the contour line (upper middle), and then polygon area (upper right) was divided by the exact area to make the envelope vs. surface ratio (ESR). Nuclei with a ratio of 1.05 or larger were defined as dysmorphic (abnormal). d Percentages of dysmorphic nuclei in normal (MJ90) and HGPS (AG11513) cells. Both cell strains were at their young stages, less than 50 % of their respective in vitro replicative life span