Dentin Matrix Protein 1, a Target Molecule for Cbfa1 in Bone, Is a Unique Bone Marker Gene
作者:Jian Q. Feng、Jianghong Zhang、Sarah L. Dallas、Yongbo Lu、Shuo Chen、Xiaoyu Tan、Michael Owen、Stephen E. Harris、Mary Macdougall
DOI:10.1359/jbmr.2002.17.10.1822
日期:——
Dentin matrix protein 1 (Dmp1), a phosphoprotein highly linked to dentin formation, has also been reported to be expressed in the skeleton. However, the role of Dmp1 in skeletal tissues remains unclear. To clarify the role of Dmp1 in bone formation, we characterized the expression profile of Dmp1 in bone and cartilage and examined whether Dmp1 expression was regulated by core‐binding factor a1 (Cbfa1). Studies of fetal rat calvarial (FRC) cell cultures showed that the expression of Dmp1 was associated closely with “bone nodule” formation and mineralization in vitro. In situ hybridization studies were performed to examine the spatial and temporal expression patterns of Dmp1 during development in mouse embryos from 12.5 day postcoitus (dpc) to 8 weeks postnatal; these studies showed that Dmp1 first appeared in hypertrophic cartilage cells, followed by osteoblasts, and later was expressed strongly in osteocytes. The expression profiles of Cbfa1 and Dmp1 overlapped in both cartilage and bone during development, with Cbfa1 preceding Dmp1. Examination of Dmp1 expression in Cbfa1−/− mice revealed that Dmp1 was absent in the developing bones of Cbfa1‐null mice, whereas there was essentially no change in Dmp1 expression in the arrested tooth bud. Transient transfection studies showed forced expression of Dmp1 under the control of Cbfa1 and gel shift data indicated the presence of a functional osteocalcin‐specific element (OSE)‐2 response element in the Dmp1 proximal promoter region. However, in vitro promoter studies suggested that regulation of Dmp1 by Cbfa1 was not mediated by direct binding of Cbfa1 to this site and may be through indirect mechanisms. These studies highlight Dmp1 as a unique marker gene for osteoblastic differentiation. The close association of Dmp1 and Cbfa1 in the developing skeleton suggests that Dmp1 may play an important role in bone formation.
牙本质基质蛋白1(Dmp1)是一种与牙本质形成高度相关的磷蛋白,据报道,它也存在于骨骼中。然而,Dmp1在骨骼组织中的作用尚不清楚。为了阐明Dmp1在骨形成中的作用,我们分析了Dmp1在骨骼和软骨中的表达特征,并研究了Dmp1的表达是否受核心结合因子a1(Cbfa1)的调控。对胎鼠颅骨(FRC)细胞培养的研究表明,Dmp1的表达与“骨结节”的形成和体外矿化密切相关。为了研究小鼠胚胎从交配后12.5天(dpc)到出生后8周发育过程中的时空表达模式,我们进行了原位杂交研究;这些研究表明,Dmp1首先出现在肥厚软骨细胞中,随后出现在成骨细胞中,最后在骨细胞中强烈表达。在发育过程中,Cbfa1和Dmp1在软骨和骨骼中的表达特征重叠,Cbfa1先于Dmp1。对Cbfa1 −/−小鼠中Dmp1表达的研究表明,在Cbfa1 −/−小鼠发育中的骨骼中不存在Dmp1,而在停滞的牙芽中Dmp1的表达几乎没有变化。瞬时转染研究表明,在Cbfa1的调控下,Dmp1被强制表达,凝胶迁移数据显示,在Dmp1近端启动子区域