It is widely accepted that, in amniotes, WNTs secreted by the dorsal neural tube form a concentration gradient that regulates somite patterning and myotome organisation. Here, Olivier Serralbo and Christophe Marcelle challenge this assumption and uncover a novel mode of long-range WNT signalling in which WNTs are delivered to their target sites by migratory neural crest cells (p. ). The researchers first show that WNT1 protein is present on the surface of early migrating neural crest cells (NCCs) in the chick embryo. Furthermore, they demonstrate that the migration of NCCs is required for correct myotome organisation and for the WNT1-dependent activation of WNT11 in a somite derivative known as the dorsomedial lip (DML). These processes, in turn, are dependent on expression of the heparin sulphate proteoglycan GPC4 by NCCs; knockdown of GPC4 in NCCs, but not in DML cells, causes a reduction in WNT11 expression in the DML, highlighting a crucial role for GPC4 in donor but not receiving cells. Overall, these findings suggest a model in which WNT proteins are loaded onto migratory NCCs and are physically delivered to the receiving cells of the DML in a GPC4-dependent manner.
