Figure 4. Tension dependence of cell shape in metaphase.

(a) Confinement force (red) recorded over time while a parallel plate confinement assay was performed on a HeLa cell in the presence of 10 µM blebbistatin. The blue region indicates when the cell was illuminated with blue light to photo-inactivate blebbistatin. Spikes in the force trace at 3 and 8 minutes indicate the recording of mCherry confocal z-stacks. The confinement height (black) is plotted below. (b) Normalized photo-inactivation induced changes in the properties of blebbistatin treated HeLa cells in metaphase (n = 13). Crosses indicate experimental measurements whereas circles indicate relative changes predicted by theory for the case of finite contact angle (black circle: φ = 45° → 31.4°, red circle: φ = 10° → 7.06°). Black bars indicate the mean of experimental data points. Changes in contact angle due to tension rise were calculated according to Eq. 2. Surface tension γ was anticipated to rise from 0.6 to 1.2mNm⁻¹ with a cell volume of 4800 µm³ and a cantilever height h_AFM of 12 µm.