Blebbing of chromatin from nucleus to cytoplasm in senescent cells is associated with loss of nuclear envelope integrity. (A) Herniation of H3K27me3-positive chromatin into the cytoplasm of OIS cells. Yellow boxed area is magnified in bottom panels. Bars: (top panels) 10 µm; (bottom panels) 5 µm. (B) Quantitation of lamin B1 gaps or herniations in OIS. Mean ± SEM, n = 2; P < 0.01. (C) Isolated nuclei of senescent cells are permeable to both 70- and 500-kD dextrans, indicating impairment of the barrier function of nuclear envelope. Dark nuclei exclude fluorescent dextran. Bars, 10 µm. (D) Quantitation of results from C. Mean ± SD, n = 4; P < 0.000001 for both 70- and 500-kD dextrans. (E) Representative OIS SAHF+ nucleus showing dextran permeability. Bars, 10 µm. (F) Quantitation of dextran 70 uptake in SAHF+ and SAHF− OIS cells. P < 1.9 × 10−5. (G) In individual nuclei, chromatin extrusion and dextran intrusion occurred in close physical proximity. Right-hand panels are expanded from yellow boxed areas on the left. Bars: (left) 10 µm; (right) 2 µm.
