Revisiting the Origin of the Vertebrate Hox14 by Including Its Relict Sarcopterygian Members
vertebrate Hox clusters. In contrast to Hox1-13 that are globally regulated by the ‘‘Hox code’’ and are often phylogenetically conserved, vertebrate Hox14 members were only recently revealed to be present in an African lungfish, a coelacanth, chondrichthyans and a lamprey, and decoupled from the Hox code. In this study we performed a PCR-based search of Hox14 members from diverse
vertebrates, and identified one in the Australian lungfish, Neoceratodus forsteri. Based on a molecular phylogenetic analysis, this gene was designated NfHoxA14. Our real-time RT-PCR suggested its hindgut-associated expression, previously observed also in cloudy catshark HoxD14 and lamprey Hox14a. It is likely that this altered expression scheme was established before the Hox cluster
quadruplication, probably at the base of extant vertebrates. To investigate the origin of vertebrate Hox14, by including this sarcopterygian Hox14 member, we performed focused phylogenetic analyses on its relationship with other vertebrate posterior Hox PGs (Hox9-13) as well as amphioxus posterior Hox genes. Our results confirmed the hypotheses previously proposed by other studies that vertebrate Hox14 does not have any amphioxus ortholog, and that none of 1-to-1 pairs of vertebrate and amphioxus posterior Hox genes, based on their relative location in the clusters, is orthologous.
- ISSN: 0022-104X