Embryonic development involves a series of cell adhesive interactions that provide mechanical and instructive information required for morphogenesis. The ADAMs family of membrane-anchored proteins, containinga disintegrinandmetalloprotease domain, is well suited for participating in such developmental events. They encode not only a potential adhesive function, through an integrin-binding disintegrin domain, but also a potential antiadhesive function, through a zinc-dependent metalloprotease domain. In order to investigate the role of ADAMs in early development we cloned a cDNA encoding a novel member of the ADAM family from aXenopus laevisneurula stage library. We call this cDNA, and the 915-amino-acid protein it encodes, ADAM 13. X-ADAM 13 RNA is expressed during embryogenesis from the midblastula stage through tadpole stage 45. X-ADAM 13 is localized to somitic mesoderm and cranial neural crest cells during gastrulation, neurulation, and in tail bud stages. Sequence analyses of the X-ADAM 13 metalloprotease and disintegrin domains indicate that the protein is likely to be involved in both proteolytic and cell-adhesive functions. The X-ADAM 13 sequence is most closely related to that of mouse meltrin α, which is implicated in myoblast fusion. Our data suggest that X-ADAM 13 may be involved in neural crest cell adhesion and migration as well as myoblast differentiation.