Science - 16.08.2019

Arp2/3 knockout (KO) mouse by crossing the
Arpc4fl/flmouse ( 30 ) with the Villin:CreERT2
line. Arpc4 depletion (fig. S8A) also decreased cell
displacement along the villi (Fig. 4, C and D),
without affecting crypt cell numbers, cell-cell
junction integrity, or the apicobasal polarity (fig.
S8, B to E). Inhibition of migration after CK-666
treatment was more pronounced in the upper
than in the lower villus region (Fig. 4B). This
agreed with the theoretical model, which predicted
that inhibition of active migration would have
a more pronounced effect in the upper villus re-
gion (fig. S7A).
Furthermore, the CK-666–treated tissue den-
sity profile matched our model prediction, abrogat-
ing the density increase at the villus top seen in
controls (Fig. 4, E to G, and fig. S7, E and F).
Arpc4-KO produced a similar cell density profile
as CK-666 (fig. S8F), whereas the villus length
was unaffected in both cases (figs. S7G and S8G).
To validate the predicted roles of mitotic pres-
sure and active migration in generating pressure
and tension forces, respectively, we performed
laser cut experiments. HUhitreatment led to an
increase in tissue tension (i.e., decrease in pres-
sure) on villi, whereas Arp2/3 inhibition led to a
decrease in tissue tension (Fig. 4H). This sup-
ports our two-tier model of mitotic pressure and
Arp2/3-dependent tensile migratory forces (Fig. 4I).
Maintenance of a functional intestinal barrier
( 31 ) requires tightly regulated epithelial renewal.
Dysregulation of either proliferation, migration,
or extrusion could lead to pathologies, such as
inflammatory diseasesand tumor formation ( 32 ).
Here, we showed that Arp2/3-driven active mi-
gration occurs along the villus. We showed that

intestinal epithelial cells exhibit dual polarity—

apicobasal and front-back—characterized by actin-

rich basal protrusions oriented in the direction

of migration. We propose that active migratory

forces are a key component in the homeostatic

renewal of the adult gut epithelium.

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ACKNOWLEDGMENTS

We thank J.-F. Joanny, D. Louvard, G. Montagnac, J. Rosenblatt,

R. Galupa, and all members of the DMV lab for helpful

discussions and critical reading of the manuscript. We thank

A. M. Lennon-Dumenil for providing the Arpc4fl/flmouse strain

and R. Adelstein for the GFP-NMHCII-A strain. We thank O. Renaud

for help with imaging and image processing. We acknowledge

the Cell and Tissue Imaging facility (PICT-IBiSA) and Animal

Facility, Institut Curie.Funding:This work was supported by ERC-

2012-StG_20111109 grant STARLIN (D.M.V.) and ANR-16-CE13-

0016-01 grant HOMEOGUT (D.M.V.).Author contributions:D.K.

and D.M.V. conceived of the study and designed all experiments.

Experiments were performed by D.K., S.R., and F.E.M. Data

analysis was done by D.K., B.G., and E.H. Mouse colony

management and transgenesis was done by F.E.M. Modeling

was done by E.H. O.L. wrote a macro for protrusion orientation

analysis. D.K., Y.B., E.H., and D.M.V. wrote the manuscript.

Competing interests:The authors declare no competing interests.

Data and materials availability:All data in the paper are

presented in the main text or in the supplementary materials.

SUPPLEMENTARY MATERIALS

science.sciencemag.org/content/365/6454/705/suppl/DC1

Materials and Methods

Theory Note

Figs. S1 to S8

Table S1

References ( 33 – 51 )

Movies S1 to S4

2 July 2018; resubmitted 6 May 2019

Accepted 3 July 2019

10.1126/science.aau3429

Krndijaet al.,Science 365 , 705–710 (2019) 16 August 2019 6of6

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