Eph/ephrin signaling system, which regulates the organization of tissues in vertebrates, was already present in unicellular organisms prior to animals, contrary to what was previously thought, as researchers from the Neurosciences Institute in Alicante just discovered.
The passage from a world populated by individual microscopic cells to another in which the first animals formed by many cells inhabited was an important evolutionary leap.
Eph receptors and their interaction partners, ephrins, constitute a receptor-ligand intracellular signaling system. This signaling system influenced the evolution of cell adhesion mechanisms that made the transition from single-cell to multicellular organisms more complex, promoting the segregation of different cell populations.
The passage from a world populated by individual microscopic cells to another in which the first animals formed by many cells inhabited was an important evolutionary leap. In this transition, the union of similar cells and the separation of different cells was essential for the appearance and development of different tissues in animals.
In this context, Eph receptors and ephrines should have an ancestral function in cell-cell interactions that contributed to the formation of borders between different cell types. This research, published in the journal Molecular Biology and Evolution, also includes the participation of David Wilkinson, an expert in Ephs and Ephrines, of the Francis Crick Institute in London.
“Until now it was believed that the oldest Eph/ephrin signaling systems were in cnidarians, a group of relatively simple animals to which jellyfish and corals belong. But we have discovered that its origin is much older; and that they were already present in organisms prior to the appearance of animals,” says Angela Nieto, director of the study.
“We have identified similar molecules in coanoflagellates, unicellular organisms closely related to animals. In addition, the predicted three-dimensional structure for the Eph receptor and the epinephrine of these organisms shows that they could bind as they do in animals and, therefore, a rudimentary Eph/ephephine signaling in coanoflagellates could already occur,” adds Aida Arcas, First signatory of this work.
Even in more primitive animals
Coanoflagellates are a small group of unicellular eukaryotes, sometimes colonial, that are of great phylogenetic importance, since they are considered the closest unicellular relatives of the animals themselves or metazoans, which form the animal kingdom.
This study also shows that sponges, which are the oldest animals, possess more than 70% of the genes that in humans Ephs/ephrin signaling pathways participate. Therefore, it is very likely that in the most primitive animals there were mechanisms of separation of cell populations similar to those found in vertebrates.