Cuticular collagen genes from the parasitic nematode Ostertagia circumcincta

The nematode cuticle is a multifunctional structure whose roles include exoskeleton and barrier between the animal and its environment. It is an extracellular matrix which consists predominantly of small collagen-like proteins. For those species studied, these cuticular collagens are encoded by a multigene family. In the free living nematode Caenorhabditis elegans, this family has approximately 100 members. Our data indicate a gene family of similar size in the parasitic nematode Ostertagia circumcincta. We have characterised a pair of tandemly duplicated collagen genes from O. circumcincta, colost-1 and colost-2, which we believe to be the direct homologues of col-12 and col-13, a tandemly duplicated pair previously identified in C. elegans. The interspecies comparison of these homologues indicates regions of extreme conservation. We conclude that the gene duplication event that resulted in the creation of col-12 and col-13 in C. elegans is most likely the same duplication that generated colost-1 and colost-2 in O. circumcincta, and thus this particular gene duplication precedes the divergence of the two species. These two nematode species are deeply diverged, O. circumcincta belonging to the order Strongylata and C. elegans to Rhabditata. The ability to identify direct homologues of individual cuticular collagen genes between deeply diverged species provides a powerful method for determining regions of structural importance in these small collagens. Characteristics that are conserved between homologues in divergent species, but not conserved with other members of the multigene family within one species, must relate to the specific function of that particular cuticular collagen.