Figure 4.

Temperature-induced volume transitions depend on chromatin compaction and remodeling dynamics. (A) Quantification of the relative thickness (red) and the average chromatin density (black) of the cortical chromatin shell for nuclei swollen to various degrees by PBS dilution. (Top row) DNA-stained nuclei in 100% PBS, 20% PBS, and 5% PBS. (B) Temperature-induced volume changes for nuclei under DNA degradation and histone modifications. (Top row) DNA-stained nuclei under corresponding pharmacological treatments. Nuclei treated with TSA (n = 69) and clostripain (n = 63) were significantly softer with larger TIVT than controls in PBS (n = 72). (C) Temperature-induced volume changes of nuclei versus fractal dimension. Addition of TSA (n = 44) and clostripain (n = 27) led to higher fractal dimension compared to control nuclei in PBS (n = 21) and DNase (n = 17). Error bars represent SD. (D). Temperature-induced volume changes of nuclei mediated by chromatin remodeling. Nuclei subjected to ATP addition (n = 73) or depletion (n = 96) showed less and more swelling effect, respectively, compared to the controls (n = 61). Topo II inhibition (n = 48) led to nuclear softening compared to the controls (n = 26). (Top row) DNA-stained nuclei under ATP addition or depletion, and in controls. All volume changes were measured at t = 1 s after optical stretching (laser powers = 1.7 W, $▵T_{\text{laser}}=18°\text{C}$, 1064 nm). ∗∗∗∗$p<0.0001,$ ∗∗∗$p<0.001,$ and ∗∗$p<0.01.$ Scale bars represent 5 μm. To see this figure in color, go online.