Dental enamel is the hardest tissue in the body. The enamel organic matrix, secreted by ameloblasts, is composed primarily of amelogenin proteins, which have an important role in enamel mineral crystal growth. Mutations in the amelogenin gene result in the enamel defect, Amelogenesis Imperfecta. The amelogenins are not found in other mineralizing tissues, and are produced only by enamel organ cells. Regulation of expression appears to be complex, as there is an active ameloginin gene on both the X and the Y chromosomes in bovine and human, and extensive alternative splicing of the primary transcripts has been described for several species. To better understand the regulation of expression of the bovine X-chromosomal amelogenin gene, the following specific aims are proposed: (1) To describe the molecular basis for the negative regulatin (silencing) of the X-chromosomal amelogenin gene in non-ameloblasts, using gene transfer, gel retardation, Dnase protection and mutagenesis assays; (2) To identify amelogenin gene upstream sequences (enhancers) that are regulated positively by transcription factors; (3) To determine the regulatory mechanisms for alternative splicing of bovine X-chromosomal amelogenin exon 6, by use of expression vectors and RT-PCR; and (4) To determine the regulatory mechanisms for alternative splicing of exon 3, the skipping of which appears to be developmentally regulated in bovine ameloblasts. Alternative splicing of exon 6 results in translation of LRAP (leucine rich amelogenin protein), which is highly represented in developing bovine enamel; exon 3 includes the only site for phosphorylation, but can be skipped in several species. This is a unique opportunity to study regulation of a sexually dimorphic gene that has a completely tissue specific pattern of expression.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
2R01DE010149-05A1
Application #
2015095
Study Section
Oral Biology and Medicine Subcommittee 1 (OBM)
Project Start
1992-04-01
Project End
2002-06-30
Budget Start
1997-07-01
Budget End
1998-06-30
Support Year
5
Fiscal Year
1997
Total Cost
Indirect Cost
Name
University of Pennsylvania
Department
Anatomy/Cell Biology
Type
Schools of Dentistry
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
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Chen, E; Yuan, Z A; Collier, P M et al. (1998) Comparison of upstream regions of X- and Y-chromosomal amelogenin genes. Gene 216:131-7
Collier, P M; Sauk, J J; Rosenbloom, S J et al. (1997) An amelogenin gene defect associated with human X-linked amelogenesis imperfecta. Arch Oral Biol 42:235-42
Gibson, C W; Collier, P M; Yuan, Z A et al. (1997) Regulation of amelogenin gene expression. Ciba Found Symp 205:187-97; discussion 197-9
Yuan, Z A; Collier, P M; Rosenbloom, J et al. (1996) Analysis of amelogenin mRNA during bovine tooth development. Arch Oral Biol 41:205-13

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