Cell biology: Conservation and novelty in the evolution of cell adhesion and extracellular matrix genes

New proteins and modules have been invented throughout evolution. Gene "bir th dates" in Caenorhabditis elegans range from the origins of cellular life through adaptation to a soil habitat. Possibly half are "metazoan" genes, having arisen sometime between the yeast-metazoan and nematode-chordate sep arations. These include basement membrane and cel adhesion molecules implic ated in tissue organization. by contrast epithelial surfaces facing the env ironment have specialized components invented within the nematode lineage. Moreover, interstitial matrices were likely elaborated within the vertebrat e lineage. A strategy for concerted evolution of new gene families, as well as conservation of adaptive genes, may underlie the differences between he terochromatin and euchromatin.