Enamel crystals are unique in shape, orientation and organization. They are hundreds of thousands times longer than they are wide, run parallel to each other, are oriented with respect to the ameloblast membrane at th...Enamel crystals are unique in shape, orientation and organization. They are hundreds of thousands times longer than they are wide, run parallel to each other, are oriented with respect to the ameloblast membrane at the mineralization front and are organized into rod or interrod enamel. The classical theory of amelogenesis postulates that extracellular matrix proteins shape crystallites by specifically inhibiting ion deposition on the crystal sides, orient them by binding multiple crystallites and establish higher levels of crystal organization. Elements of the classical theory are supported in principle by in vitro studies; however, the classical theory does not explain how enamel forms in vivo. In this review, we describe how amelogenesis is highly integrated with ameloblast cell activities and how the shape, orientation and organization of enamel mineral ribbons are established by a mineralization front apparatus along the secretory surface of the ameloblast cell membrane.展开更多
Enamelin （ENAM） has three putative phosphoserines （pSers） phosphorylated by a Golgi-associated secretory pathway kinase （FAM20C） based on their distinctive Ser-x-Glu （S-x-E） motifs. Fam2OC-knockout mice show s...Enamelin （ENAM） has three putative phosphoserines （pSers） phosphorylated by a Golgi-associated secretory pathway kinase （FAM20C） based on their distinctive Ser-x-Glu （S-x-E） motifs. Fam2OC-knockout mice show severe enamel defects similar to those in the Enam-knockout mice, implying an important role of the pSers in ENAM. To determine the role of pSer5s in ENAM, we characterized ENAMRgsc514 mice, in which Sers5 cannot be phosphorylated by FAM20C due to an E57〉Gs7 mutation in the S-x-E motif, The enamel microstructure of 4-week-old mice was examined by scanning electron microscopy. The teeth of 6-day-old mice were characterized by histology and immunohistochemistry. The protein lysates of the first lower molars of 4-day-old mice were analyzed by Western immunoblotting using antibodies against ENAM, ameloblastin and amelogenin. ENAMRgsc514 heterozygotes showed a disorganized enamel microstructure, while the homozygotes had no enamel on the dentin surface. The N-terminal fragments of ENAM in the heterozygotes were detained in the ameloblasts and localized in the mineralization front of enamel matrix, while those in the WT mice were secreted out of ameloblasts and distributed evenly in the outer 1/2 of enamel matrix. Surprisingly, the 15 kDa C-terminal fragments of ameloblastin were not detected in the molar lysates of the homozygotes. These results suggest that the phosphorylation of SerSS may be an essential posttranslational modification of ENAM and is required for the interaction with other enamel matrix molecules such as ameloblastin in mediating the structural organization of enamel matrix and protein-mineral interactions during enamel formation.展开更多
目的:通过构建真核表达载体,在COS-7细胞中表达人成釉蛋白基因。方法:分别将人成釉蛋白基因克隆入非融合和融合真核表达载体pcDNA 3.1和pEGFP-C3中,证实克隆正确后,用脂质体介导将载体转染哺乳动物细胞COS-7,通过免疫组织化学、W estern...目的:通过构建真核表达载体,在COS-7细胞中表达人成釉蛋白基因。方法:分别将人成釉蛋白基因克隆入非融合和融合真核表达载体pcDNA 3.1和pEGFP-C3中,证实克隆正确后,用脂质体介导将载体转染哺乳动物细胞COS-7,通过免疫组织化学、W estern B lot等方法检测成釉蛋白在哺乳动物细胞中的表达。结果:表达的绿色荧光蛋白融合蛋白所发出的荧光位于细胞浆中,胞核中无荧光,与免疫组化结果一致,说明人成釉蛋白位于细胞浆中。W estern B lot检测显示在COS-7细胞中表达的成釉蛋白的分子量为65×103,分泌至培养基中的成釉蛋白的分子量为62×103。结论:成功在哺乳动物细胞中表达了人成釉蛋白,为研究成釉蛋白合成后的修饰加工和成釉蛋白的结构,为今后进一步研究成釉蛋白结构和功能的关系奠定了基础。展开更多
基金supported by NIDCR/NIH grant projects DE011301 and DE061854
文摘Enamel crystals are unique in shape, orientation and organization. They are hundreds of thousands times longer than they are wide, run parallel to each other, are oriented with respect to the ameloblast membrane at the mineralization front and are organized into rod or interrod enamel. The classical theory of amelogenesis postulates that extracellular matrix proteins shape crystallites by specifically inhibiting ion deposition on the crystal sides, orient them by binding multiple crystallites and establish higher levels of crystal organization. Elements of the classical theory are supported in principle by in vitro studies; however, the classical theory does not explain how enamel forms in vivo. In this review, we describe how amelogenesis is highly integrated with ameloblast cell activities and how the shape, orientation and organization of enamel mineral ribbons are established by a mineralization front apparatus along the secretory surface of the ameloblast cell membrane.
基金supported by NIH grant DE026461start funding of Texas A&M University College of Dentistry
文摘Enamelin （ENAM） has three putative phosphoserines （pSers） phosphorylated by a Golgi-associated secretory pathway kinase （FAM20C） based on their distinctive Ser-x-Glu （S-x-E） motifs. Fam2OC-knockout mice show severe enamel defects similar to those in the Enam-knockout mice, implying an important role of the pSers in ENAM. To determine the role of pSer5s in ENAM, we characterized ENAMRgsc514 mice, in which Sers5 cannot be phosphorylated by FAM20C due to an E57〉Gs7 mutation in the S-x-E motif, The enamel microstructure of 4-week-old mice was examined by scanning electron microscopy. The teeth of 6-day-old mice were characterized by histology and immunohistochemistry. The protein lysates of the first lower molars of 4-day-old mice were analyzed by Western immunoblotting using antibodies against ENAM, ameloblastin and amelogenin. ENAMRgsc514 heterozygotes showed a disorganized enamel microstructure, while the homozygotes had no enamel on the dentin surface. The N-terminal fragments of ENAM in the heterozygotes were detained in the ameloblasts and localized in the mineralization front of enamel matrix, while those in the WT mice were secreted out of ameloblasts and distributed evenly in the outer 1/2 of enamel matrix. Surprisingly, the 15 kDa C-terminal fragments of ameloblastin were not detected in the molar lysates of the homozygotes. These results suggest that the phosphorylation of SerSS may be an essential posttranslational modification of ENAM and is required for the interaction with other enamel matrix molecules such as ameloblastin in mediating the structural organization of enamel matrix and protein-mineral interactions during enamel formation.
文摘目的:通过构建真核表达载体,在COS-7细胞中表达人成釉蛋白基因。方法:分别将人成釉蛋白基因克隆入非融合和融合真核表达载体pcDNA 3.1和pEGFP-C3中,证实克隆正确后,用脂质体介导将载体转染哺乳动物细胞COS-7,通过免疫组织化学、W estern B lot等方法检测成釉蛋白在哺乳动物细胞中的表达。结果:表达的绿色荧光蛋白融合蛋白所发出的荧光位于细胞浆中,胞核中无荧光,与免疫组化结果一致,说明人成釉蛋白位于细胞浆中。W estern B lot检测显示在COS-7细胞中表达的成釉蛋白的分子量为65×103,分泌至培养基中的成釉蛋白的分子量为62×103。结论:成功在哺乳动物细胞中表达了人成釉蛋白,为研究成釉蛋白合成后的修饰加工和成釉蛋白的结构,为今后进一步研究成釉蛋白结构和功能的关系奠定了基础。
