The study of white-spotting mouse mutations, which create distinct pigment patterns by affecting the maturation and survival of the neural crest-derived melanoblasts, has helped to elucidate the developmental mechanisms required for lineage determination, migration and proliferation. On p. 4665, Rao et al. reveal that Adamts20, a novel member of the ADAMTS family of secreted metalloproteinases, is mutated in belted (bt) mutant mice. These mutants are normally pigmented apart from a 'white belt' of hair that occurs near their hindlimbs. The researchers show that Adamts20 is not expressed by the neural crest-derived melanoblasts but by the mesenchymal tissue through which these cells migrate. The extensive homology between Adamts20 and GON-1, an ADAMTS family member protease that is required for distal tip cell migration in C. elegans, indicates that the role of secreted metalloproteinases in cell migration has been conserved during evolution.