Integrins play an essential role in somite adhesion to the embryonic axis.

Integrins are proteins that mediate cell adhesion, mainly to the extracellular matrix. One of the first integrins discovered belongs to the beta 1 class of avian integrins and is defined by a monoclonal antibody, CSAT. Using a whole-embryo culture system we injected nanoliter quantities of CSAT caudolateral to the last somite of early quail embryos. The CSAT antibodies, but not control antibodies, resulted in a striking lateral translocation of somites. Relatively higher doses or longer incubation times increased the severity of the effect. We conclude that somite segmentation per se is not influenced by CSAT, but that somite adhesion to axial structures requires integrin-mediated ECM adhesions.