Cadherin superfamily proteins in Caenorhabditis elegans and Drosophila melanogaster

The ability to form selective cell-cell adhesions is an essential property of metazoan cells. Members of the cadherin superfamily are important regula tors of this process in both vertebrates and invertebrates. With the advent of genome sequencing projects, determination of the full repertoire of cad herins available to an organism is possible and here we present the identif ication and analysis of the cadherin repertoires in the genomes of Caenorha bditis elegans and Drosophila melanogaster. Hidden Markov models of cadheri n domains were matched to the protein sequences obtained from the translati on of the predicted gene sequences. Matches were made to 21 C. elegans and 18 D. melanogaster sequences. Experimental and theoretical work on C. elega ns sequences, and data from ESTs, show that three pairs of genes, and two t riplets, should be merged to form five single genes. It also produced seque nce changes at one or both of the 5' and 3' termini of half the sequences. Ln D. melanogaster it is probable that two of the cadherin genes should als o be merged together and that three cadherin genes should be merged with ot her neighbouring genes. Of the 15 cadherin proteins found in C. elegans, 13 have the features of cell surface proteins, signal sequences and transmemb rane helices; the other two have only signal sequences. Of the 17 in D. mel anogaster, 11 at present have both features and another five have transmemb rane helices. The evidence currently available suggests about one-third of the cadherins in the two organisms can be grouped into subfamilies in which all, or parts of, the molecules are conserved. Each organism also has a si milar to 980 residue protein (CDH-11 and CG11059) with two cadherin domains and whose sequences match well over their entire length two proteins from human brain. Two proteins in C. elegans, HMR-1A and HMR-1B, and three in D. melanogaster, CadN, Shg and CG7527, have cytoplasmic domains homologous to those of the classical cadherin genes of chordates but their extracellular regions have different domain structures. Other common subclasses include the seven-helix membrane cadherins, Fat-like protocadherins and the Ret-lik e cadherins. At present, the remaining cadherins have no obvious similariti es in their extracellular domain architecture or homologies to their cytopl asmic domains and may, therefore, represent species-specific or phylum-spec ific molecules. (C) 2001 Academic Press.