• somitogenesis;
  • morphogenesis;
  • mesoderm;
  • integrin;
  • fibronectin;
  • adhesion;
  • migration


The morphogenesis of somites in Xenopus laevis is characterized by a complex process of cell turning that requires coordinated regulation of cell shape, adhesion, and motility. The integrin α5 subunit has been implicated in the formation of somite boundaries in organisms utilizing epithelialization to create morphologically distinct somites, but its function has not been examined in Xenopus. We used a splice-blocking morpholino to knock down expression of integrin α5 during somite formation. Loss of integrin α5 delayed somite turning and accumulation of integrin β1 at somite boundaries, and disrupted the fibronectin matrix surrounding developing somites. Irregular somite boundaries with a sparse and discontinuous fibronectin matrix formed upon eventual completion of somite turning. Recovery of somite morphology was improved, but still incomplete in far posterior somites. These data demonstrate that the role of integrin α5 in somite boundary formation is conserved in a species using a unique mechanism of somitogenesis. Developmental Dynamics 236:2713–2720, 2007. © 2007 Wiley-Liss, Inc.