1. Volume 25, Issue 2, Pages 242-250 (January 2015)
Collective Cell Motility Promotes Chemotactic Prowess and Resistance to Chemorepulsion 
Gema Malet-Engra, Weimiao Yu, Amanda Oldani, Javier Rey-Barroso, Nir S. Gov, Giorgio Scita, Loïc Dupré 
Current Biology 
Volume 25, Issue 2, Pages (January 2015)
DOI: /j.cub
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2. Current Biology 2015 25, 242-250DOI: (10.1016/j.cub.2014.11.030)
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3. Figure 1
Lymphoid Cell Clusters Are Highly Chemotactic and Resist Chemorepulsion
(A) Snapshot pictures showing JVM3 cells migrating as single cells or as clusters along a 0–100 ng/ml CCL19 gradient. See also Movie S1A and Figures S1A and S1C.
(B) Migratory tracks of clusters (≥20 cells) and single cells exposed to the indicated CCL19 concentrations. Red and black tracks indicate, respectively, motion toward and away from the chemokine source. At least 29 single cells and ten clusters were recorded over 2 hr. See also Movies S2A and S2B and Figures S1B and S1C.
(C) Forward migration index (FMI) calculated as cell (or cluster) displacement along the y axis/cell (or cluster) track length. Data are the mean ± SD of four independent experiments. ∗∗∗p < 0.001; Student’s t test.
(D) Snapshot pictures showing the fusion (red arrow) of small cell groups (cell count in white) leading to cluster assembly and onset of directional motility. See also Movie S1.
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4. Figure 2
Chemokine-Gradient-Sensing and Cell-to-Cell Adhesion Properties Underlying Chemotactic Prowess of Lymphoid Cell Clusters
(A) Snapshot pictures of a cluster of JVM3 cells expressing GFP-CCR7 (green) entering and progressing along a 0–500 ng/ml gradient of Alexa Fluor 647-CCL19 (magenta). Positions of the cluster along the gradient are depicted on the right panels. The scale bar represents 10 μm.
(B) Images of GFP-CCR7-expressing JVM3 cells (green) migrating as a single cell or in a cluster (cell position in cluster core or rim front is indicated on the right panels) along a 0–500 ng/ml gradient of Alexa Fluor 647-CCL19 (magenta). The scale bars represent 10 μm.
(C) 3D reconstruction of a GFP-actin-expressing JVM3 cell cluster exposed to a 0–500 ng/ml CCL19 gradient. Plots show the length and persistence of ten rear and ten front lamellipodial protrusions (mean ± SD) of a representative cluster.
(D) Images of a GFP-CCR7-expressing JVM3 cell cluster exposed to a 0–500 ng/ml CCL19 gradient. The perimeter of representative cells positioned in the core and rim (front or back) of the cluster are delineated (white contour line). Data are the mean ± SD of circularity (long axis/short axis; n > 25 in five independent clusters). ∗∗p < 0.005; ∗∗∗p < 0.001; Student’s t test. The scale bar represents 10 μm.
(E) 3D reconstructions of serial confocal sections of JVM3 cell clusters exposed to a 0–500 ng/ml CCL19 gradient and stained with antitotal (upper panel) or anti-high-affinity (lower panels) LFA-1 antibodies (red), phalloidin (green), and DAPI (blue). The scale bar represents 20 μm.
(F) Z projection of serial confocal sections of a JVM3 cell cluster exposed to a 0–500 ng/ml CCL19 gradient and stained with CellMask and anti-high-affinity LFA-1 antibodies. In the lower panel, the perimeter of representative cells positioned in the core and rim of the cluster are delineated (contour line). The scale bar represents 20 μm. High-affinity LFA-1 fluorescent intensity along the perimeter of core or rim cells, distinguishing the latter contact areas from free edges. The mean ± SD is indicated. ∗∗p < 0.005; ∗∗∗p < 0.001; Student’s t test. The intensity profile of high-affinity LFA-1 intensity is shown along the perimeter of the core and rim cells depicted on the corresponding picture. AU, arbitrary units.
(G) FMI and speed of clusters exposed to a 0–500 ng/ml CCL19 gradient in the presence of the LFA-1 inhibitor RWJ50271 or anti-LFA-1 antibodies. Data are the mean ± SD of four independent experiments. ∗∗p < 0.005; ∗∗∗p < 0.001; Student’s t test.
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5. Figure 3
Computational Modeling of Lymphoid Cell Cluster Chemotaxis and Analysis of Coordination Phases
(A) Scheme of a circular 2D cell cluster with chemokine-induced protrusive forces in rim cells (black arrows) that point radially outward and are proportional to the local chemokine concentration.
(B) Cluster velocities measured in the indicated CCL19 gradients as a function of cluster area. The horizontal dashed line indicates the mean velocity. See also Figures S2Ci–S2Ciii.
(C) Scheme of the random traction forces produced by the cells (black arrows), which may be either confined to the rim or uniform and either correlated or uncorrelated.
(D) Velocity variance of clusters exposed to a 0–500 ng/ml CCL19 gradient, as a function of cluster area. Green line: the fit using a crossover to correlated forces below ∼20 cell sizes. Red lines: the fit for noise that is always uncorrelated. See also Figures S2Bi–S2Biii.
(E) The measured FMI for the same data set as in (D), compared to the model calculations that use the fits shown in (D).
(F) Snapshots showing examples of the running, rotation, and random phases of a representative JVM3 cell cluster migrating along a 0–500 ng/ml CCL19 gradient. Thin color-coded arrows indicate individual nuclei directions over 20 s intervals. The large yellow arrow indicates the mean direction of the nuclei whereas the green arrow indicates the cluster direction. The length of the large green arrow indicates the value of group polarization. See also Movie S3C.
(G and H) Variations of group polarization, angular momentum, and cluster speed over time. The color-coded bar at the bottom of the speed plot indicates the phase status of the cluster at the given time points (red, running; blue, rotation; green, random).
(I) 2D feature space of group polarization and angular momentum, showing running, rotation, and random coordination phases of a representative cluster of JVM3 cells exposed to a 0–500 ng/ml gradient of CCL19.
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6. Figure 4
Endocytic-Dependent Dynamic Changes of Cell-Surface CCR7 Are Coupled to Intracluster Cell Turnover and Required to Overcome Chemorepulsion
(A) Confocal sections of GFP-CCR7 (green)-expressing JVM3 cell clusters stained with CellMask (magenta) and exposed to the indicated CCL19 concentrations. Right panels are heatmaps of the GFP-CCR7/CellMask ratio. The scale bar represents 10 μm.
(B) GFP-CCR7/CellMask ratio (mean ± SEM) in leader and nonleader cells of clusters migrating along a 0–500 ng/ml CCL19 gradient. Leader cells correspond to the first row of a 120°-wide sector oriented toward the chemokine source. ∗p < 0.05; Student’s t test.
(C) Oscillation of the GFP-CCR7/CellMask ratio in a representative cell of a cluster migrating along a 0–500 ng/ml CCL19 gradient. Insets represent a series of still images of the cell (heatmaps of the GFP-CCR7/CellMask ratio) as it is losing its leader position during cluster rotation (arrows). The scale bar represents 10 μm.
(D) Expression levels of dynamin-2 and clathrin in JVM3 cells transfected with the indicated siRNA. CCR7 endocytosis measured as the percentage of remaining cell-surface CCR7 at the indicated time points after treatment with CCL19 (or CCL21 where indicated) in nontreated JVM3 cells (NT) or JVM3 cells treated with dynasore or transfected with dynamin-2 and clathrin siRNA. Data are the mean ± SEM (n = 3).
(E) Migratory tracks of clusters and single cells exposed to a 0–500 ng/ml CCL19 gradient. Red and black tracks indicate, respectively, motion toward and away from the chemokine source. For each condition, at least 33 single cells and 17 clusters were recorded over 2 hr. See also Movies S4A and S4B.
(F) FMI and speed of clusters and individual cells treated as indicated and exposed to a 0–500 ng/ml CCL19 gradient. The mean ± SEM is indicated. ∗p < 0.05; ∗∗∗p < 0.001; Student’s t test. See also Movie S4C.
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