SNELL, EA*; HOLLAND, PWH: Evolution of the non-integrin 67kDa Laminin Receptor: insights from choanoflagellates

The change from unicellularity to multicellularity is one of the most fundamentally important steps in animal evolution. Currently there is a paucity of information indicating the genetic and developmental changes that occurred during this jump from protists to metazoans. One particularly key change is the evolution of epithelial cell sheets, supported by basal lamina composed of extracellular matrix proteins such as collagen and laminin. The basal lamina provides a structural framework for animal body plans, while the constituent proteins and their receptors also have roles in cell communications. To gain a better understanding of how these lamina evolved, we have conducted an EST screen on one of the closest unicellular relatives of the metazoans: the choanoflagellate, Monosiga ovata. We have identified a gene orthologous to the non-integrin 67kDa laminin receptor gene in metazoans. Comparison of deduced amino acid sequence between choanoflagellates and animals reveals stepwise evolution of the laminin-binding function in metazoans.