Meeting Abstract
P1.58 Jan. 4 Evolution of Pharyngeal Arch Specification in Teleosts LE PABIC, Pierre*; STELLWAG, Edmund; SCEMAMA, Jean-Luc; BROTHERS, Shelby; East Carolina University; East Carolina University; East Carolina University; East Carolina University stellwage@ecu.edu
The nature of structures located in the hindbrain and pharyngeal arches of vertebrates are determined, at least in part, through the action of Hox paralog group 2 (PG2) genes. In sarcopterygians, the hoxa2 gene alone appears to specify structures derived from the 2nd pharyngeal arch, including the middle ear stapes as well as elements of the hyoid and styloid processes. By contrast, in zebrafish either of only two Hox PG2 genes, hoxa2b or b2a, can specify 2nd pharyngeal arch derived structures, which indicates that in zebrafish, unlike the case in sarcopterygians, Hox PG2 genes function redundantly in specification of 2nd pharyngeal arch fate. We previously reported that the striped bass possesses three Hox PG2 genes, including hoxa2a, a2b and b2a. Based on expression patterns of these three genes, we concluded that the two HoxA cluster genes likely function alone or together to specify the 2nd pharyngeal arch. Results from our laboratory, including the cloning and expression analysis of three Hox PG2 genes from the Nile tilapia show that these three genes (hoxa2a, a2b and b2a) are all expressed in the 2nd pharyngeal arch. Reanalysis of the expression patterns for the three striped bass Hox PG2 genes revealed that they are also expressed in the 2nd pharyngeal arch, albeit with somewhat different temporal and spatial expression patterns than their Nile tilapia orthologs. Although we have not yet determined the functional specification of the three Hox PG2 genes from striped bass or Nile tilapia, the expression of all three genes in the 2nd pharyngeal arches of these species suggests that they all may play a role in specification of the 2nd pharyngeal arch.
