Islets are clusters of endocrine cells in the pancreas that contain specialised cell types responsible for the secretion of hormones such as insulin and glucagon. During the development of the pancreas, progenitors of islet cells delaminate from the embryonic ductal epithelium then migrate before maturation, so that the endocrine cell clusters become scattered throughout the pancreatic tissue. On p. 3744, Seung K. Kim and colleagues now uncover a mechanism controlling the migration of these cells and the subsequent positioning of islets. Using transgenic mouse lines and protein-soaked beads, they identify the semaphorin ligand Sema3a as a long-range guidance signal for migrating foetal islet cells. They show that endocrine cells express high levels of the Sema3a receptor neuropilin 2, allowing them to sense and transduce this chemoattractant. Intriguingly, this mechanism is similar to that which controls neuronal migration in the developing brain, and thus uncovers a conserved mechanism for directing the migration of progenitor cells during organogenesis.
