The molecular phylogeny of eph receptors and ephrin ligands.
BACKGROUND
The tissue distributions and functions of Eph receptors and their ephrin ligands have been well studied, however less is known about their evolutionary history. We have undertaken a phylogenetic analysis of Eph receptors and ephrins from a number of invertebrate and vertebrate species.


RESULTS
Our findings indicate that Eph receptors form three major clades: one comprised of non-chordate and cephalochordate Eph receptors, a second comprised of urochordate Eph receptors, and a third comprised of vertebrate Eph receptors. Ephrins, on the other hand, fall into either a clade made up of the non-chordate and cephalochordate ephrins plus the urochordate and vertebrate ephrin-Bs or a clade made up of the urochordate and vertebrate ephrin-As.


CONCLUSIONS
We have concluded that Eph receptors and ephrins diverged into A and B-types at different points in their evolutionary history, such that primitive chordates likely possessed an ancestral ephrin-A and an ancestral ephrin-B, but only a single Eph receptor. Furthermore, ephrin-As appear to have arisen in the common ancestor of urochordates and vertebrates, whereas ephrin-Bs have a more ancient bilaterian origin. Ancestral ephrin-B-like ligands had transmembrane domains; as GPI anchors appear to have arisen or been lost at least 3 times.
Mellott
Dan O
DO
Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada. dan.mellott@gmail.com
Burke
Robert D
RD
D000818:Animals; D001665:Binding Sites; D002450:Cell Communication; D036342:Ephrins / Q000235:genetics; D019143:Evolution, Molecular; D006801:Humans; D008024:Ligands; D016013:Likelihood Functions; D009432:Neural Crest / Q000196:embryology / Q000378:metabolism*; D010802:Phylogeny; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D020239:Receptor Cross-Talk; D036081:Receptors, Eph Family / Q000235:genetics*; D016415:Sequence Alignment; D017421:Sequence Analysis; D014561:Urochordata; D014714:Vertebrates
D036342:Ephrins; D008024:Ligands; D011505:Protein-Tyrosine Kinases; D036081:Receptors, Eph Family