Meeting Abstract
Study of the origin of evolutionary novelties is central to understanding the history of life. With advancements in developmental genetics, we can investigate the genetic basis of evolutionary novelties and their subsequent transformations. The gas bladder, derived from lungs of the common ancestor of bony vertebrates, originated within ray-finned fishes and is important for efficient buoyancy control. As homologous organs, the gas bladder and lungs share many similarities; however, the defining difference between the two organs is the location of budding from the anterior foregut; gas bladders bud from the dorsal wall and lungs from the ventral wall. Therefore, we are investigating whether the inversion of budding location is paralleled by a ventral-to-dorsal inversion of gene expression patterns. To determine the genes involved in gas bladder development and their spatial expression, we used laser-capture microdissection to isolate dorsal and ventral foregut tissue from larval bowfin (Amia calva) at three key developmental stages and sequenced the tissue expression profiles. Bowfin are an early-diverging ray-finned fish that possess a dorsal gas bladder and therefore, are an ideal species to study early gas bladder evolution. We identified the genes differentially expressed between dorsal and ventral tissues, and from this set, we characterized when and where known mouse lung-regulatory genes are expressed and whether they exhibit an inverted pattern during gas bladder development compared to lung development. We found Tbx5 and Gata4, both of which are involved in lung development, to have dorsoventrally restricted expression patterns. In particular, Tbx5 is highly expressed in the dorsal mesoderm surrounding the gas bladder bud, whereas during mouse lung development, it is expressed in the ventral mesoderm.
