Tissue morphogenesis results from the interplay between cell growth and mechanical forces.
While the impact of forces on cell proliferation has been fairly well characterized, the inverse
relationship is much less understood. Here we investigated how traction forces vary during cell cycle
progression. Cell shape was constrained on micropatterned substrates in order to distinguish
variations in cell contractility from cell size increase. We performed traction force measurements of
asynchronously dividing cells expressing a cell-cycle reporter, to obtain measurements of contractile
forces generated during cell division. We found that forces tend to increase as cells progress through
G1, before reaching a plateau in S phase, and then decline during G2. This biphasic behaviour
revealed a previously undocumented specific and opposite regulation of cell contractility during each
cell cycle stage.