A macrophage relay for long-distance signaling during postembryonic tissue remodeling

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Science  24 Mar 2017:
Vol. 355, Issue 6331, pp. 1317-1320
DOI: 10.1126/science.aal2745

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Cell projections set up pigment pattern

Macrophages eliminate dead or dying cells and identify and destroy invading microbes. However, they also exhibit nonimmune functions in development and homeostasis. Eom and Parichy show that macrophages are essential for postembryonic remodeling during adult pigment stripe formation in zebrafish (see the Perspective by Guilliams). Pigment cells relay signal-containing vesicles via cellular projections from one class of cell to another. Without macrophages, this signal relay fails, and adult stripes are disorganized.

Science, this issue p. 1317; see also p. 1258


Macrophages have diverse functions in immunity as well as in development and homeostasis. We identified a function for these cells in long-distance communication during postembryonic tissue remodeling. Ablation of macrophages in zebrafish prevented melanophores from coalescing into adult pigment stripes. Melanophore organization depends on signals provided by cells of the yellow xanthophore lineage via airinemes, long filamentous projections with vesicles at their tips. We show that airineme extension from originating cells, as well as vesicle deposition on target cells, depend on interactions with macrophages. These findings identify a role for macrophages in relaying long-range signals between nonimmune cells. This signaling modality may function in the remodeling and homeostasis of other tissues during normal development and disease.

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