Cadherin evolution and the origin of animals

摘要: The question of how animals evolved from a unicellular ancestor has challenged evolutionary biologists for decades. Because cell adhesion and signaling are required multicellularity, understanding these cellular processes will provide key insights into the origin animals. A critical finding is that choanoflagellates, closest living relatives animals, express members cadherin superfamily. Cadherins pivotal animal were previously thought to be unique making them crucial transition multicellularity. Importantly, presence cadherins in choanoflagellates allows consideration their ancestral function progenitor To gain insight structure cadherins, I reconstructed domain content last common metazoans. Conservation diverse protein domains choanoflagellate Monosiga brevicollis metazoan suggests served both adhesive functions. find two M. containing an combination MBCDH1 close paralog, MBCDH2, localize actin-filled microvilli feeding collar. Interestingly, abundance changes response bacterial food availability. In vitro studies, as well experiments performed heterologous culture system, suggest does not mediate homophilic context like some thus may play role signaling. Taken together, data interactions with extracellular environment, including recognition capture prey. hypothesize co-opted cell-cell proteins interpreted responded cues.