| 1593 Dentin Matrix Protein-1 (Dmp-1) is Not Essential For Initiation of Apatite Crystal Formation But is Critical For Formation of Normal Mineral Structure | ||
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Y. LU1, S.L. DALLAS1, Y. MISHINA2, S.E. HARRIS3, L.F. BONEWALD1, and J.Q. FENG1, 1 University of Missouri-Kansas City, USA, 2 Laboratory of Reproductive and Developmental Toxicology, Research Triangle Park, NC, USA, 3 School of Dentistry, Univ. of Missouri-Kansas City, USA Objectives: Dentin matrix protein-1 (Dmp1) is an acid phosphoprotein thought to be important for initiation of mineralization. Recently we have cloned the mouse Dmp1 genomic sequence and generated transgenic mice in which the Dmp1 gene has been rendered non-functional. These Dmp1-null mice display profound abnormalities in the skeleton and tooth. One of the most striking features of the Dmp1-null mice is a severe abnormality in mineralization of the bone, cartilage, dentin and enamel. In order to understand the mechanisms whereby deletion of Dmp1 causes the abnormal phenotype, we examined calvarial cells isolated from Dmp1 deficient and wild-type mice. Methods: Mouse calvarial cells were isolated using collagenase digestion with EDTA treatment as described by Harris et al. (1995). The cells were cultured in a-MEM medium with b-glycerophosphate and ascorbic acid for 2 weeks. Time and dose response of these cells to TGFb and Bmp2 were examined with regards to effects on cell proliferation, nodule formation, mineralization and mRNAs expression of genes important to bone formation. Results: There were no differences in response to TGFb and Bmp2 with respect to proliferation between wild-type and Dmp1 null cells. However, there were greater numbers of nodules in the Dmp-1 deficient calvarial cells but these nodules were less organized than wild-type. Northern analysis showed that the levels of Cbfa1, bone sialoprotein, and osteopontin are significantly lower in Dmp-1 deficient cells. In contrast, osteocalcin mRNA is significantly higher. Conclusions: Dmp1 is not essential for initiation of mineralization but is critical for size, organization, structure, and formation rate of nodules.. These early studies also suggest that absence of Dmp-1 has significant effects on expression of genes important for skeletal growth and maturation. This work is supported by NIH-NIDCR grants DE00455, DE13480 (JQF), and DE13221 (MM), and UM research Board. | ||
| Seq #201 - Senior Category 11:00 AM-12:15 PM, Saturday, 15 March 2003 Henry B. Gonzalez Convention Center Exhibit Hall C | ||
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