NSF Postdoctoral Fellowship in Biology FY 2021: Uncovering the Mechanisms of Convergent Tooth Loss in Frogs

Paluh, Daniel J, Gainesville FL

Investigators

Abstract

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. Teeth are present in most living vertebrates. However, complete tooth loss has evolved in a few groups of fishes, reptiles, and mammals. Though the arrangement and condition of amphibian teeth has been poorly studied, recent work shows that frogs have lost teeth more than 20 times. The mechanisms underlying tooth loss in frogs are unknown, but examining possible developmental, genetic, and environmental factors will provide insight to how predictable and repeatable this process is from an evolutionary point of view. The aim of this project is to determine if there is a core set of genes required for tooth development, and to test if the environment (temperature) can affect tooth development. The fellowship will facilitate mentorship training by fostering research opportunities for undergraduate students. Digital anatomy resources will be created for middle school teachers and students to provide real examples of evolution through natural selection using museum specimens. The proliferation of teeth in fishes and amniotes is mediated by at least four major signaling pathways, and the loss of different signals arrests dental development and underlies tooth loss in birds, turtles, and some mammals. With phylogenetically widespread tooth loss and separate evolutionary losses on upper and lower jaws, frogs offer an unparalleled opportunity for investigating the mechanisms of repeated trait loss. The fellow will use immunohistochemistry, in situ hybridization, and transcriptomics to characterize dental development in amphibians and assess if different signals arrest tooth development among species that have independently lost teeth. Within tetrapods, enamel and dentin are found only in teeth, and these tissues are formed by proteins encoded by tooth-specific, non-pleiotropic genes. Comparative genomics will be used to identify if enamel and dentin genes have become non-functional in toothless frogs via novel inactivating mutations. Environmental factors may impact dental anatomy by altering developmental rate. An experimental approach will be used to test if one such factor, temperature, impacts the anatomy and expression patterns of frog dentition. Creation of digital resources for anatomy education and PI participation in mentoring undergraduate students and outreach will broaden the impact of the project. 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.