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Abstract of Chris Organ 's NIH Postdoctoral Fellowship


Evolution of BMP Genes 2 and 4 in Archosaurs

Evolution of birds from non-avian theropods involves fusion of many skeletal elements, including intratendinous ossification in many groups. Paleontology, development, and genetics have been integrated by using bone morphogenic proteins to address digit identity in birds and their evolution from theropod dinosaurs. But the genetic basis underlying the evolutionary trend of skeletal element fusion (co-ossification) in birds is not well understood. Bone morphogenic proteins (BMPs), especially BMP2 and BMP4, are well known for their integral role in skeletal ossification during embryogenesis in vertebrates. In birds, BMP4 has recently been found to regulate beak morphology during an adaptive radiation and BMP2 is now known to control the structure of feathers and scales. Given the roles of BMP2 and BMP4 in the development of bone in general and of avian structures, such as feathers and beak shape, in particular it is likely that these genes likely played an important role in the evolution of birds from non-avian theropod dinosaurs. Furthermore, birds make an excellent model to investigate the evolution of bmp genes because there is a well known fossil record that documents bone phenotype on the lineage to modern birds. Many extraordinary feathered dinosaur fossils discovered in China recently have driven a renaissance of histology documenting bone growth and physiology during the evolution of birds from non-avian dinosaurs. Despite these findings, the genetic basis behind this evolution has remained unexplored. This project will use comparative genomics to elucidate the evolution of the osteogenic genes bmp2 and bmp4 in archosaurs as they relate to the evolution of skeletal co-ossification on the line to birds. These data will test the hypothesis that bmp2 and bmp4 have been under selection to co-ossify the skeletal system during the evolution of Aves.


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