MCCAULEY, D.W.; BRONNER-FRASER, M.; California Institute of Technology; California Institute of Technology: Independent duplication of BMP24 genes in the lamprey Petromyzon marinus.

Bone morphogenetic proteins (BMPs) were identified initially for their role in formation of bone and cartilage. However, they were found subsequently to play important roles in regulating morphogenesis in both vertebrates and invertebrates. BMP2 and BMP4, members of the transforming growth factor-beta (TGF-beta) superfamily of signaling molecules, have been shown to play an important role in neural development. In vertebrates, there is evidence that during gastrulation, BMP signaling is important in positioning the neural plate. Early in development, BMP4 is expressed in the non-neural ectoderm adjacent to the open neural plate. BMP antagonists have been found to block expression of neural crest markers and cause expansion of the neural plate while exogenous BMP can induce neural crest. In order to examine the roles of these genes in a basal vertebrate, we have isolated orthologs to BMP2/4 from the lamprey, Petromyzon marinus. While gnathostomes contain only a single copy of BMP2 and BMP4, we find that P. marinus contains at least 3 members of this family. Phylogenetic analysis indicates these genes diverged independently in lamprey and gnathostomes and probably existed as a single ancestral gene in the common ancestor to gnathostomes and agnathans. We have examined the developmental expression patterns of PmBMP24A, PmBMP24B, and PmBMP24C. Conserved expression domains of these genes suggest that certain functions of vertebrate BMP signaling were established early during the evolution of vertebrates, while other expression domains appear only in lamprey, suggesting agnathan-specific roles as well.