The purpose of this project is to elucidate the structure and mechanism of formation of higher order assemblies of enamel matrix proteins and their influence on mineralization and crystal organization in vitro. We propose that organized mineral stuctures are generated within organized super-assemblies of matrix proteins in cooperation with other macromolecules that guide crystal growth and shape. Our working hypothesis is that higher order assemblies of full-length amelogenin, in association with soluble acidic proteins (e.g., enamelin and ameloblasrin), regulate the nucleation, growth, shape, and arrangement of initial enamel mineral crystals. Under appropriate mineralizing conditions, such assemblies support the formation of parallel arrays of very thin ribbons of enamel mineral. The growth of these enamel ribbons in thickness and width is immediately inhibited by soluble hydrophobic enamel proteins (e.g. sparingly soluble amelogenins) which adsorb onto specific faces of the growing crystals. It is further hypothesized that the subsequent onset of growth of these mineral ribbons during tissue maturation is controlled by the degradation of these enamel protein inhibitors by specific enamel proteinases. To improve our understanding of how matrix proteins regulate mineralization in tissues like enamel, we propose to characterize specific enamel matrix components with respect to their ability to form higher-order assemblies that ultimately regulate organized mineralization. Specifically, we propose to characterized the ability of key enamel matrix proteins to bind to mineral surfaces (Aim 1), to regulate crystal shape and kinetics of crystal growth (Aim 2), and to induce calcium phosphate formation in vitro (Aim 3). Importanly, these findings; will be integrated with biophysical studies to determine the structure and mechanism of formation of proposed higher order assemblies of the full-length amelogenin (Aim 4) and the mechanism by which such assemblies regulate the formation of organized mineral structures, similar to that of dental enamel (Aim 5). Long term, such information should provide new insights for the development of bio-inspired materials and novel approaches for mineralized tissue repair and regeneration.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
5R01DE016376-02
Application #
7104885
Study Section
Special Emphasis Panel (ZRG1-MOSS-A (02))
Program Officer
Shum, Lillian
Project Start
2005-08-01
Project End
2010-07-31
Budget Start
2006-08-01
Budget End
2007-07-31
Support Year
2
Fiscal Year
2006
Total Cost
$405,465
Indirect Cost
Name
Forsyth Institute
Department
Type
DUNS #
062190616
City
Cambridge
State
MA
Country
United States
Zip Code
02142
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Zhang, Zichao; Gutierrez, Diana; Li, Xiao et al. (2013) The LIM homeodomain transcription factor LHX6: a transcriptional repressor that interacts with pituitary homeobox 2 (PITX2) to regulate odontogenesis. J Biol Chem 288:2485-500
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Le Norcy, E; Kwak, S-Y; Wiedemann-Bidlack, F B et al. (2011) Potential role of the amelogenin N-terminus in the regulation of calcium phosphate formation in vitro. Cells Tissues Organs 194:188-93
Fang, Ping-An; Margolis, Henry C; Conway, James F et al. (2011) Cryogenic transmission electron microscopy study of amelogenin self-assembly at different pH. Cells Tissues Organs 194:166-70

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