Tracing the evolution of nectin and nectin-like cell adhesion molecules

Nectin and nectin-like cell adhesion molecules (collectively referred as nectin family henceforth) are known to mediate cell-cell adhesion and related functions. While current literature suggests that nectins are prevalent in vertebrates, there are no in-depth analyses regarding the evolution of nectin family as a whole. In this work, we examine the evolutionary origin of the nectin family, using selected multicellular metazoans representing diverse clades whose whole genome sequencing data is available. Our results show that this family may have appeared earlier during metazoan evolution than previously believed. Systematic analyses indicate the order in which various members of nectin family seem to have evolved, with some nectin-like molecules appearing first, followed by the evolution of other members. Furthermore, we also found a few possible ancient homologues of nectins. While our study confirms the previous grouping of the nectin family into nectins and nectin-like molecules, it also shows poliovirus receptor (PVR/nectin-like-5) to possess characteristics that are intermediate between these two groups. Interestingly, except for PVR, the other nectins show surprising sequence conservations across species, suggesting evolutionary constraints due to critical roles played by these proteins.