Zheng Li, Iohara Koichiro, Ishikawa Masaki, Into Takeshi, Takano-Yamamoto Teruko, Matsushita Kenji, Nakashima Misako
Laboratory of Oral Disease Research, National Institute for Longevity Sciences, National Center for Geriatrics and Gerontology, Aichi 474-8522, Japan.
Biochem J. 2007 Jul 1;405(1):69-75. doi: 10.1042/BJ20070104.
Osterix, a zinc-finger-containing transcription factor, is required for osteoblast differentiation and bone formation. Osterix is also expressed in dental mesenchymal cells of the tooth germ. However, transcriptional regulation by Osterix in tooth development is not clear. Genetic studies in osteogenesis place Osterix downstream of Runx2 (Runt-related 2). The expression of Osterix in odontoblasts overlaps with Runx3 during terminal differentiation in vivo. Runx3 down-regulates Osterix expression in mouse DPCs (dental pulp cells). Therefore the regulatory role of Runx3 on Osterix expression in tooth development was investigated. Enforced expression of Runx3 down-regulated the activity of the Osterix promoter in the human embryonic kidney 293 cell line. When the Runx3 responsive element on the Osterix promoter, located at -713 to -707 bp (site 3, AGTGGTT) relative to the cap site, was mutated, this down-regulation was abrogated. Furthermore, electrophoretic mobility-shift assay and chromatin immunoprecipitation assays in mouse DPCs demonstrated direct functional binding of Runx3 to the Osterix promoter. These results demonstrate the transcriptional regulation of Osterix expression by Runx3 during differentiation of dental pulp cells into odontoblasts during tooth development.
osterix是一种含锌指结构的转录因子，是成骨细胞分化和骨形成所必需的。osterix也在牙胚的牙间充质细胞中表达。然而，osterix在牙齿发育中的转录调控尚不清楚。成骨过程中的遗传学研究表明osterix在Runx2（Runt相关蛋白2）的下游。在体内终末分化过程中，成牙本质细胞中osterix的表达与Runx3重叠。Runx3下调小鼠牙髓细胞（DPCs）中osterix的表达。因此，研究了Runx3在牙齿发育中对osterix表达的调控作用。在人胚肾293细胞系中，Runx3的强制表达下调了osterix启动子的活性。当osterix启动子上相对于帽位点位于-713至-707 bp（位点3，AGTGGTT）的Runx3反应元件发生突变时，这种下调作用被消除。此外，小鼠DPCs中的电泳迁移率变动分析和染色质免疫沉淀分析表明Runx3与osterix启动子存在直接的功能结合。这些结果证明了在牙齿发育过程中，牙髓细胞向成牙本质细胞分化期间，Runx3对osterix表达的转录调控作用。
