Inherited diseases of dental enamel formation are grouped under the designation of amelogenesis imperfecta (AI). About 25% of all amelogenesis imperfecta (AI) cases are caused by the genes encoding four enamel extracellular matrix proteins, AMELX, ENAM, MMP20, and KLK4. Recently we identified mutations in FAM83H that cause AI in six different families suffering from amelogenesis imperfecta. This demonstrates that FAM83H is necessary for proper enamel formation. Virtually nothing is known about the Fam83h protein. Our objective is to learn the roles played by Fam83h in normal and defective enamel formation. Hypotheses: Because the phenotype in people with FAM83H mutations is limited to developing teeth, we hypothesize that Fam83H is expressed during odontogenesis. Because all of the AI- causing FAM83H mutations are dominant nonsense mutations that terminate translation in the last coding exon (exon 5), we further hypothesize that the Fam83h interacts with other cellular proteins to form functional complexes. We propose four Specific Aims: SA 1: To characterize the temporal and spatial pattern of Fam83h expression during odontogenesis and to determine its subcellular localization. SA 2: To isolate Fam83H protein for structural and functional characterization. SA 3: To identify Fam83H interacting proteins. SA 4: To determine if the expression of truncated Fam83h interferes with amelogenesis. Approach: The temporal and spatial pattern of Fam83h expression during odontogenesis is determined by in situ hybridization and immunohistochemistry. Recombinant and native Fam83h are used in structural and functional studies. Fam83h interacting proteins are identified using the yeast two-hybrid system and validated using a mammalian two-hybrid system, co- immunoprecipitation, and Far Western analyses. Normal and mutated Fam83h are expressed in ameloblasts as transgenes and their effects on enamel formation characterized. Heath Relatedness: Patients with inherited enamel defects (AI) have painful, disfigured teeth, lower self-esteem, and perceive themselves as having an inferior quality of life. The discovery that FAM83H is critical for dental enamel formation is a significant advance in our understanding of the etiology of AI. The proposed research may lead to a breakthrough in our understanding of important activities within ameloblasts and the discovery of new candidate gene(s) for AI.

Public Health Relevance

Our group has determined that defects in FAM83H (family with sequence similarity 83 member H) on chromosome 8 cause severe enamel malformations (autosomal dominant hypocalcification amelogenesis imperfecta). Our objectives are to discover the normal function of Fam83h and how defects in this protein result in enamel malformations. Our long term goal is to advance understanding of normal and pathological tooth formation to stimulate improvements in the public's oral health.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
5R01DE019622-05
Application #
8441387
Study Section
Special Emphasis Panel (ZRG1-MOSS-K (09))
Program Officer
Scholnick, Steven
Project Start
2009-04-01
Project End
2015-03-31
Budget Start
2013-04-01
Budget End
2015-03-31
Support Year
5
Fiscal Year
2013
Total Cost
$345,250
Indirect Cost
$121,787
Name
University of Michigan Ann Arbor
Department
Dentistry
Type
Schools of Dentistry
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
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Kweon, Young-Sun; Lee, Kyung-Eun; Ko, Jiyeon et al. (2013) Effects of Fam83h overexpression on enamel and dentine formation. Arch Oral Biol 58:1148-54
Simmer, J P; Papagerakis, P; Smith, C E et al. (2010) Regulation of dental enamel shape and hardness. J Dent Res 89:1024-38
Ding, Y; Estrella, M R P; Hu, Y Y et al. (2009) Fam83h is associated with intracellular vesicles and ADHCAI. J Dent Res 88:991-6