Figure 1.

The dynamics of nuclear flattening during early cell spreading. (A–C) Vertical cross sections of a nucleus in a cell that settles and spreads on the substratum. The images were captured using x-z laser scanning confocal fluorescence microscopy; the nucleus is expressing GFP-histone H1. Three phases were discernible in the nuclear flattening process: (A) a settling phase where the basal surface of the nucleus contacted the basal cell surface and started to spread, the height was roughly constant during this time; (B) a collapse of the top surface where the basal surface of the nucleus did not spread much; and (C) a widening phase where the basal surface of the nucleus continued to spread and contributed to nuclear widening; the height was roughly constant in this phase. Scale bar is 10 μm. (D) Plot shows nuclear height and contact length in (A–C) with time. (E–G) Nuclei did not flatten when cell spreading was prevented by inhibitors of actin assembly, cytochalasin-D or latrunculin-A, based on nuclear aspect ratio (height divided by the length of the major-axis in the x-y plane) after 1 h spreading in the presence of the drugs (n ≥ 31, ^∗p < 0.05; all comparisons are with untreated control). Scale bar in (E) is 20 μm in the x-y view and 5 μm in x-z view. All data are shown as mean ± SEM. To see this figure in color, go online.