FIGURE 1.

Schematic representation of different models to study in vivo cell migration. Red arrows show the direction of migrating cells. (A) Example of a cell (in blue) migrating in vitro on an ECM coated dish. As the cell moves, it reads mechanical cues from the ECM (purple arrows). (B) Example of a migrating cell (in blue) moving in vivo through complex environments composed of different cell types (in orange and pink) and extracellular matrix (ECM, in green). As the cell moves, it reads mechanical cues from the ECM (purple arrows) and the neighboring cells (black arrows). (C) Drosophila macrophage germ band invasion: (Top) Macrophages (in blue) migrate through the developing embryo and invade the germ band. (Bottom) Macrophages (in blue) invade the germ band by crawling through an ECM track laid between the ectoderm (in orange) and the mesoderm (in pink). (D) Xenopus Neural crest migration: (Top) Neural crest (NC) migrates as streams (in blue) along the embryo. (Bottom) NC cells (in blue) undergo epithelial to mesenchymal transition and chase after the placodes (in orange). The NC crawls on an ECM track (in green), which is laid on top of the mesoderm (in pink) and the placodes (in orange). (E) Drosophila Border cell migration: the border cell cluster (in blue) migrates through the middle of the egg chamber towards the posterior end, squeezing through the neighboring nurse cells (in orange). (F) Xenopus Multiciliated Cell intercalation: (Top) Multiciliated cells migrate to form the embryonic epidermis. (Bottom) Multiciliated cells (MCC) move from the inner epithelial layer (in pink) towards the outer epithelial layer (in orange), where they integrate the tissue by pushing the neighboring cells aside (black arrows).