Slow integrin-dependent migration organizes networks of tissue-resident mast cells

Immune cell locomotion is associated with amoeboid migration, a flexible mode of movement, which depends on rapid cycles of actin polymerization and actomyosin contraction1. Many immune cells do not necessarily require integrins, the major family of adhesion receptors in mammals, to move productively through three-dimensional tissue spaces2,3. Instead, they can use alternative strategies to transmit their actin-driven forces to the substrate, explaining their migratory adaptation to changing external environments4–6. However, whether these generalized concepts apply to all immune cells is unclear. Here, we show that the movement of mast cells (immune cells with important roles during allergy and anaphylaxis) differs fundamentally from the widely applied paradigm of interstitial immune cell migration. We identify a crucial role for integrin-dependent adhesion in controlling mast cell movement and localization to anatomical niches rich in KIT ligand, the major mast cell growth and survival factor. Our findings show that substrate-dependent haptokinesis is an important mechanism for the tissue organization of resident immune cells.

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March 2021
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Sample size
No statistical methods were used to predetermine sample size. They were determined based on our previous publications, prior experience or pilot experiments.
Data exclusions For most experiments: No data exlcusion methods were used. For image analysis of mast cell proximity to arterioles: Cells at ACTA2-positive structures without characteristic arteriolar morphology (capillaries) were manually excluded from the analysis. Sc-RNAseq analysis: A very small cell subset showed additional macrophage features (cluster 10) (ED Fig. 5c), which we excluded from further analysis.

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Reproducibility of the experimental findings was verified using biological replicates and independent experiments. The numbers are indicated in the respective figures (individual data points). Most experimental findings were replicated by independent experiments through several lab members.
Randomization Experimental groups were defined by inhibitor treatment or by the genotype. Mast cells and mast cell clusters were randomly chosen for tracking, cell size analysis or cluster size determination, respectively.

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Both male and female mice were used for experiments. In comparative experiments, control and knockout mice were sex-and agematched littermates.
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Mouse breeding and husbandry were performed at the Max Planck Institute of Immunobiology and Epigenetics, Freiburg, in accordance with the guidelines provided by the Federation of European Laboratory Animal Science Association and as approved by German authorities (Regional Council of Freiburg). Mice were only used for organ removal after euthanasia by carbon dioxide exposure and thus not subject to experimental procedures and ethical approval according to §4 (3) Tierschutzgesetz.
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Flow Cytometry
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