MCCAULEY, D.W.*; BRONNER-FRASER, M.: Pax Gene Expression in Ectodermal Placodes of the Lamprey

Ectodermal placodes contribute to the cranial ganglia and sense organs of the head and, together with neural crest cells, represent defining features of the vertebrate embryo. The identity of different placodes appears to be specified in part by the expression of different Pax genes, with Pax3/7 class genes being expressed in the trigeminal placode of mice, chick, frogs and fish, and Pax2/5/8 class genes expressed in the otic placode. Here, we present the cloning and expression pattern of Pax-7 and Pax-2 in the lamprey Petromyzon marinus. In the lamprey, these genes are expressed in the trigeminal and otic placodes, respectively, as well as other structures characteristic of vertebrate Pax genes. These results suggest conservation of Pax genes and placodal structures in basal and higher vertebrates.