To first verify the presence of DNA damage in our reprogrammable progeria model, adult tail tip fibroblasts (FBs) were isolated from the 4Fj Ercc1∆/− (D/KO) and 4Fj Ercc1+/+ (WT) mice, stained for the DNA damage marker γH2AX, and imaged with confocal laser microscopy. Here, ERCC1 is linked to progeroid syndrome.