Amelogenin Protein Evolution and Functional Heterochrony

University Of Illinois At Chicago, Chicago IL

Investigators

Abstract

This research is concerned with the evolution of tooth enamel and enamel proteins. Amelogenin is the major protein of tooth enamel and directly affects the growth and habit of enamel hydroxyapatite mineral crystals. However amelogenin also occurs in organisms such as sea urchins that have teeth but lack enamel and toads which lack teeth. One principal in evolutionary biology is that relatively small genetic alterations can have profound affects on morphogenesis and development. This project will test whether the evolution of the amelogenin gene is the causal agent for the evolution of tooth enamel. This project focuses on the functional significance of the amelogenin C-domain. The C-domain is part of the central hydrophobic amelogenin core rich in proline and glutamine tandem repeats that change significantly in size, structure, and composition among organisms as diverse as sea urchins, sharks, fish, lizards, frogs, and mice. As tooth enamel has evolved, enamel crystals have proceeded from short randomly oriented patterns to long and parallel prisms. In order to gain an understanding how specific structural domains of the amelogenin molecule might affect alterations in enamel biomineralization during vertebrate evolution, the fate and function of the amelogenin molecule in vertebrate lineages will be studied. The hypothesis to be tested is whether the evolution of enamel crystals from short and randomly oriented patterns to long and parallel-oriented prisms is directly linked to the evolution of increasingly sophisticated amelogenin C-domains facilitating the organization of complex supra-molecular amelogenin subunit-compartments. Aims are 1) to correlate enamel/enameloid crystal dimensions to amelogenin temporo-spatial localization and protein domain configuration, 2) to trace the evolution of amelogenins from pro-amelogenin to teleo-amelogenin in vertebrate lineages in the context of amelogenin protein function, 3) to compare the effects of pro-amelogenin with the effects of teleo-amelogenin on enamel matrix conformation and crystal growth and habit. This research will shed new light on mechanisms involved in vertebrate enamel formation and will generate further understanding of the evolution of complex structural genes as well as mechanisms of biomineralization. Insight into biomineralization processes has potential applications in nanotechnology particularly with regard to the fabrication, assembly, and design of new materials .