FIGURE 3:

Increased heterochromatin via methylstat treatment increases nuclear rigidity and decreases nuclear blebbing in lamin B1 null nuclei. (A) Representative images of heterochromatin markers in MEF WT and LB1–/– nuclei untreated or treated with 1 µM methylstat for 48 h. Plot quantifies the change in relative fluorescence for H3K27me³ and H3K9me^2,3 (n = 102, 106, and 112, respectively). Western blots confirm increased markers for heterochromatin while lamins remain unchanged for both MEF WT and LB1–/– treated with methylstat (Supplemental Figure 4, C and D). Addition of methylstat to cells in culture did not perturb cell growth (Supplemental Figure 3F). (B) Nuclear spring constants for MEF V–/– cells untreated and methylstat-treated via micropipette-based micromanipulation force measurements (n = 9 and 15, p < 0.005, t test). Data for untreated cells are the same as in Figure 1. (C) Graph of percentage of nuclei displaying nuclear blebbing for MEF WT, LB1–/–, LB1–/– plus vehicle (DMSO), and LB1–/– treated with methylstat (n = 907, 901, 402, and 691, respectively). Scale bar = 10 µm. Error bars represent standard error. Asterisk denotes statistically significant difference (p < 0.01), and bars with different numbers of asterisks are also significantly different.