During vertebrate gastrulation, mesodermal and endodermal cells internalise through the blastopore and then migrate in different ways to establish the internal and external organisation of the embryo. Wnt/planar cell polarity signalling controls the mesodermal cell migration but what regulates the endodermal cell movements? Mizoguchi and colleagues now report that, during zebrafish gastrulation, the chemokine Sdf1, which is released by mesodermal cells, controls the dorsal migration of endodermal cells, which express the Sdf1 receptor Cxcr4 (see ). Morpholino knockdown of cxcr4a or sdf1a/sdf1b (sdf1) inhibits the directional migration of cxcr4a-expressing endodermal cells, whereas misexpressed Sdf1 attracts cxcr4a-expressing endodermal cells. Using a transgenic line that expresses GFP in the endodermal cells, they also show that Sdf1/Cxcr4 signalling regulates the formation and orientation of the characteristic filopodial processes that, the researchers suggest, may help the endodermal cells decide their direction of migration. These results provide important new insights into the control of endodermal migration during zebrafish gastrulation.
