Extended Data Fig. 7: Analysis of collagen network alignment during collective migration.
From: Self-generated gradients steer collective migration on viscoelastic collagen networks
a. Montage of a cluster on a fluorescent collagen network (single z-slice on network surface). Scale Bar: 50μm. HH:MM. b. Montage of cluster in a overlaid with the local collagen alignment. Rods: local nematic order (orientation indicates mean collagen fiber orientation, length indicates order parameter magnitude S, color indicates orientation with respect to cluster center of mass (90∘ is oriented toward the cluster, 0∘ is oriented perpendicular to the cluster). Scale rod: S = 1. Image length scale as for a. c. Polar plot of nematic order within 50μm of the cluster boundary (mean ± SD over all time points). P-value: Rayleigh test of uniformity. For a-c, representative images/data from n=28 cells, N=3 independent experiments. d. Live imaging of clusters using AiryScan super-resolution microscopy. Upper Panels: Brightfield images with segmentation and front-to-back regions in the direction of migration. Lower Panels: AiryScan images of TAMRA-labeled collagen at different z-positions. e. Box plot of the collagen fiber nematic order from AiryScan images. Dots represent individual clusters. For d,e, representative images/data from n=11 clusters, N=3 independent experiments. f,g. Montages of clusters migrating on thick deformable (f) or thin non-deformable (g) aligned collagen networks. Lower Panels: Overlaid cluster migration trajectories, adjusted to start at the origin (0,0) and rotated with respect to collagen alignment direction. Scale Bars: 100μm. HH:MM. Representative images from n=66, 86 clusters, N=4, 4 independent experiments h. Boxplot of orientational index along the collagen alignment direction for conditions in f,g. One-way ANOVA: p=0.00113. *p < 0.05, ***p < 0.001 for Tukey HSD post-hoc test (p=0.340, < 0.001, 0.0184). i. Boxplots of mean instantaneous speed and coefficient of persistence for conditions in f,g. For h,i, data from n=114, 66, 86 clusters, N=6, 4, 4 independent experiments. Thick isotropic data is the same as Fig. 1f. One-way ANOVAs: p=0.0180, 7.83e-6. *p < 0.05, **p < 0.01, ***p < 0.001 for Tukey HSD post-hoc test (p=0.567, 0.00919, 0.0393; p=0.0413, < 0.001, 0.0190).
