Fig. 2.

Wrinkling and volume shrinkage of the nucleus. (A) A GFP–lamin-A-transfected MEF treated with trypsin showing the progressively wrinkling nucleus as the cell detaches from the collagen-coated glass-bottomed dish. The upper panels are DIC and GFP channel merged images and the lower panels are enlarged GFP channel images showing details of nuclear morphology. (B) Trypsinization of a GFP–lamin-A-transfected MEF pre-treated with nocodazole. The nucleus undergoes a similar shape change to the control. (C) Experimental measurement and theoretical prediction of nuclear volume shrinkage during cell detachment. The theoretical curve is explained in the Materials and Methods. The data are mean±s.e.m. obtained from 37 live cells (>10 cells per trial, repeated three times). Inset: the change in the surface area of the nucleus during detachment. (D) The shrinkage in nuclear volume of nocodazole pre-treated MEF cells during cell detachment. The volume shrinks to a lesser extent than in control cells. Results are mean±s.e.m. for 31 cells (5–10 cells per trial, repeated four times) were tested and results are (E) Nuclear volume shrinkage in attached MEF cells treated with ML-7 (mean±s.e.m., 10 cells were tested). Upon treatment the nuclear volume slightly increased, suggesting that myosin exerts a compressive force on the nucleus. (F) Nuclear volume shrinkage in attached MEF cells treated with low levels of LatB (mean±s.e.m., 10 cells were tested). The nuclear volume initially increased slightly, and then as the cell detached, began to decrease. Taken together with data in E, this suggests that actomyosin stress fibers are compressing the nucleus in the attached state. Scale bars: 10 μm.