Figure 1.
Cross sections of a F9 WT aggregate (A) and of a F9 aggregate (B). The staining is for
-catenin, scale bars, 10
. (C) Schematic representation of the cortical contractions at the cell-extracellular medium interface (
), at the cell-cell interface (
) and of the adhesion energy J.
and
increase the tissue surface tension, whereas
decreases it (see Eq. 2). (D) Closer view of two F9
cells in contact. The difference between the interfacial tensions at the cell-cell
and cell-extracellular medium
interfaces gives the aggregate surface tension (
).
increases the surface tension whereas
decreases it. Scale bar, 5
. (E-F) Cartoons of cell-cell contacts in the case of F9 WT cells (E) and F9
cells (F). The presence of
-catenin at cell-cell junction is described as a catalyzer for actin reorganization at cell-cell junctions.
Figure 2.
Quantitative dependence of TST on contractility.
(A) Side view on a stereomicroscope of a F9 WT aggregate compressed between two parallel plates. Scale bar 150 . (B) Force signal obtained when subjecting a F9 WT aggregate to 2 successive compressions. (C) The value of the TST for different cell lines and drugs as obtained from tissue surface tensiometry experiments. Error bars represent standard errors on the mean (95
confidence interval of the mean) and n is the number of experiments, each experiment corresponding to several successive compressions.
Figure 3.
Contractility dependent TST still predicts sorting out and envelopment.
Phase contrast and fluorescence images representing configurations at different stages of the sorting out (A–C) and envelopment (D–F) processes. (A–B) Phase contrast and fluorescence images correspond to 72 hours after mixing F9 and F9 dissociated cells in hanging drops. (C) Control fluorescence of a F9/F9 mixture after 72 hours. (D–E) Engulfment of a F9/F9
pair of aggregates 3 hours (D) and 29 hours (E) after the aggregates were brought in contact and allowed to fuse. (F) Final configuration (72 hours) of a F9/F9 pair of aggregates (control). Left right thick double arrow indicates simultaneous recording in phase and fluorescence. Rightwards thick arrow indicates evolution with time. Scale bars, 100
m.
Figure 4.
Tissue fluidity versus contractility.
(A–B) Images of two fusing F9 WT aggregates corresponding to the beginning and the end of the analyzed period, showing in red the neck's diameter 2. (C) Plot of
versus
(time
aggregate initial radius). Blue points represent experimental data and red line represents linear fit with the slope defining the visco-capillary velocity
. (D) Measurements of
for different cell lines and drugs. Error bars represent the standard errors of the mean (95
confidence interval of the mean) and n is the number of experiments. (E) Fluidity deduced from
and
(i.e. defined as
) for untreated and treated aggregates and interpreted as the inverse of the viscosity. (F) Measurements of
as a function of temperature for F9 WT and F9
aggregates. Error bars represent the standard errors of the mean (95
confidence interval of the mean) and n is the number of experiments.