Figure 6.

Nuclear flattening can be reversed by detachment of the cell from the substratum. Trypsinization of cells rounded the nucleus (A) in a remarkably short time of a few seconds. Importantly, the nuclear rounding closely followed the cell rounding—the dynamics of height changes (gray circles) and changes in contact length of the basal cell surface (black circles) are similar (B). Scale bar is 10 μm for both panels in (A). This concept was tested further in (C) by trypsinizing cells at one-third the dose of the trypsin concentration used in (A). The nucleus rounded much more slowly (several minutes) and closely reflected the rounding up of the cell body (the nuclear height and cell contact length are shown in (D). Thus, the degree of cell spreading determines the degree of nuclear rounding during cell detachment. Scale bar is 20 μm for both panels. All data are shown as mean $\pm$ SEM.