Comment on “Connexins evolved after early chordates lost innexin diversity”

Gap junctional (GJ) intercellular channels are an important way of intercellular communication. Currently, two unrelated families of GJ proteins, innexins/pannexins, and connexins, are known, either or both of which are present in most multicellular animals. A striking exception is the echinoderms which have functional GJs but until recently were believed to be lacking both innexins and connexins, which suggests the presence of the third, yet the unknown family of GJ proteins. In the recent work Welzel and Schuster (Welzel and Schuster, 2022) have reported several putative innexins and one connexin from echinoderms, therefore undermining such a hypothesis. Here we provide evidence showing that all reported connexin and innexin sequences from echinoderms are cross-species contaminations, indicating that a search for a third GJ protein family is still a subject of immediate scientific research interest.