The overall goal of the proposed study is to take advantage of the unique phylogenetic position of the lamprey, Petromyzon marinus, to address fundamental issues of developmental and molecular evolution in the vertebrate lineage. Lampreys are the simplest extant vertebrates, situated phylogenetically between the cephalochordates (represented by amphioxus) and the gnathostomes (represented by mammals, birds, reptiles, amphibians, and fish). Morphologically, lampreys share several characteristics with their gnathostome sister group, including multiple brain divisions, neural crest and its derivatives, neurogenic placodes, pharyngeal arches, and a cartilaginous endoskeleton, but they lack jaws and paired appendages and retain a relatively simple axial morphology. Genetically, lampreys also appear to be less complex than gnathostomes, having undergone fewer duplications of developmental regulatory genes. Lampreys are thus a perfect system with which to investigate developmental and molecular events associated with early vertebrate evolution. Dr. Langeland has led in recent efforts to establish lampreys as a viable system for comparative developmental genetics. There are two basic thrusts to this proposal: 1) to use gene expression studies in lamprey embryos to investigate fundamental aspects of the evolution of vertebrate head patterning, and 2) to use gene phylogeny studies to test whether duplications of select regulatory genes accompanied vertebrate origins. The Langeland laboratory will clone and characterize members of the goosecoid, Emx, and snail/Slug gene families in P. marinus. These genes are excellent markers for three key developmental innovations that accompanied vertebrate origins: the establishment of the head organizer, the elaboration of rostral brain patterning, and the acquisition and diversification of cephalic neural crest. Comparative expression analyses of these genes during lamprey embryogenesis will allow more precise reconstruction of developmental events associated with vertebrate origins. In addition, determination of the copy number of these genes in lampreys, and analysis of their phylogenetic relationships with their gnathostome and protochordate homologs, will provide important evidence concerning whether widespread gene duplications, or even whole genome duplication, facilitated vertebrate origins. This research will take place at a four-year undergraduate liberal arts college. Extensive involvement of undergraduates in all phases of the project will help maintain the strong record of the host institution and of the principal investigator in integrating research with teaching, and in preparing future Ph.D.s in the life sciences.
