NSF Postdoctoral Fellowship in Biology FY 2021: Assessing potential parallel evolution of heterodonty via co-option of shared developmental modules

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This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2021, Integrative Research Investigating the Rules of Life Governing Interactions Between Genomes, Environment and Phenotypes. The fellowship supports research and training of the Fellow that will contribute to the area of Rules of Life in innovative ways. Parallel evolution is when organisms evolve similar traits using the same ancestral genes. Detailed study of how parallel evolution works is rare, but it is important for understanding how often evolution repeats itself. One possible example of parallel evolution that would be particularly useful is heterodonty, a difference in tooth size/shape along the jaw. This feature can be observed in embryos and in fossils, providing information on its underlying genetics and evolution through deep time. Heterodonty is best known in mammals, but it has also evolved in many reptiles. This research will determine whether heterodonty develops using the same genes in mammals and reptiles. The Fellow will use µ-CT scans of reptile jaws to identify their distinct tooth regions and then observe normal tooth development in reptile embryos to see if it involves the same genes as in mammals. If this is the case, these genes in reptile embryos will be blocked to assess their necessity for developing heterodonty. This research will provide the Fellow with training necessary to build a research program combining techniques from embryonic development and paleontology. Additionally, this project will involve outreach to diverse members of the public through the Yale Peabody Museum and an online video series connecting pop culture with major concepts in evolution. Mammalian heterodonty is generated via regionalized expression of homeobox transcription factors in the developing dental epithelium, and this expression pattern is also known in chicks. This research will determine whether that same expression pattern was also co-opted for the development of reptilian heterodonty. The Fellow will use segmented linear regression to identify boundaries between toothrow regions in µ-CT scans of heterodont reptile jaws. Then, in situ hybridization will assess whether homeobox gene expression coincides with the identified tooth regions in reptile embryos. The Fellow will also use bead implantation to evaluate the necessity of homeobox genes in delineating regions of heterodont reptilian toothrows. This project will train the Fellow in molecular developmental techniques to complement her experience with functional morphology and paleontology. The Fellow will use this wide range of expertise to educate the public about functional morphology and development.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.