Osteoblast and Odontoblast Specific Regulatory Action of Runx2 for Bone and Tooth

Runx2 对骨和牙齿的成骨细胞和成牙本质细胞特异性调节作用

• 批准号: 8316770
• 负责人: Mitra D Adhami
• 金额: $ 4.8万
• 依托单位: UNIVERSITY OF ALABAMA AT BIRMINGHAM
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8316770
• 关键词: Ablation; Address; Age; Ameloblasts; Apical; Bone Development; Bone Matrix; Cartilage; Cell Lineage; Cells; Chondroblast; Chondrocytes; Cleidocranial Dysplasia; Collagen Type I; Complex; Dendrites; Dental Enamel; Dental Research; Dentin; Deposition; Development; Disease; Dysplasia; Embryo; Embryonic Development; Fibroblasts; Foundations; Gene Deletion; Gene Expression; Genes; Genetic; Health; Homeostasis; Human; Individual; Knock-out; Knockout Mice; Lead; Left; Link; Maintenance; Mesenchymal Stem Cells; Mesenchyme; Modeling; Molecular; Morphology; Mus; Mutation; Odontoblasts; Odontogenesis; Oral; Osteoblasts; Osteoclasts; Osteocytes; Osteogenesis; Osteopenia; Perinatal; Phase; Phenotype; Play; Process; Property; Reporting; Research; Role; Skeletal Development; Skeleton; Staging; Supernumerary Tooth; System; Testing; Therapeutic; Tissues; Tooth Germ; Tooth structure; Transgenic Mice; Transgenic Model; Transgenic Organisms; Variant; bone; cell type; clavicle; clinical application; craniofacial; in vivo; inhibitor/antagonist; intramembranous bone formation; long bone; malformation; mineralization; mouse model; novel; novel diagnostics; novel therapeutics; osteogenic; overexpression; postnatal; promoter; recombinase; skeletal; skeletal abnormality; skeletal dysplasia; skeletogenesis; tool; transcription factor

DESCRIPTION (provided by applicant): Runx2 is a critical component of skeletal development. Global knock-out studies have proven the role of Runx2 as a regulator for skeletal and tooth development. Runx2-null mice are born with a complete lack of mineralization, and tooth germs that arrest at the late cap/early bell stage. Furthermore, it has been shown that Runx2 is required for commitment from mesenchymal progenitor cells to the osteoblast, chondrocyte, and odontoblast lineages. Mutations in Runx2 gene lead to skeletal abnormalities in humans, such as Cleidocranial Dysplasia, which arises from haploinsufficiency of Runx2. This disorder is characterized by skeletal and craniofacial anomalies. Thus, understanding the specific functions of Runx2 has immense potential for clinical applications. Attempts to study the cell and tissue specific functions of Runx2 and its role in postnatal development have been unsuccessful. Transgenic mouse models manifest significant variation in their phenotypes, by contradicting the basic understandings of the role of Runx2 in normal development. For example, transgenic studies overexpressing Runx2 after the osteoblast-commitment phase report osteopenia, suggesting that Runx2 acts as an inhibitor in late stages of osteogenesis. However, it is known that gene expression of Runx2 increases throughout embryonic development, and Runx2 maintains high expression in postnatal development. I propose to employ a novel Runx2 floxed mouse model to accomplish Runx2 deletion in a cell type specific manner. We have previously confirmed this as a valid model for Runx2 gene ablation. For cell-type specific gene deletion, I will use the 2.3kb Type I Collagen promoter to drive Cre expression. Using this model, I will determine the function of Runx2 specifically in osteoblasts for skeletogenesis, and identify its role in odontoblasts for tooth formation. Furthermore, the expected viability of this mouse model passed the major postnatal developmental age will permit invaluable advances in bone and dental research. Our hypothesis is that Runx2 is required for maintenance of mature osteoblast phenotype and postnatal bone acquisition, and that the function of Runx2 in odontoblasts is essential for odontoblast maturation, and proper dentin and tooth formation. I will address this hypothesis by in vivo and ex vivo approaches by two specific aims: 1) Osteoblast specific regulatory role of Runx2 for skeletogenesis; and 2) Requirement of Runx2 for odontoblast maturation and tooth formation. The information obtained from these studies will provide a foundation for understanding the molecular mechanisms involved in both normal and abnormal osteogenic and dental development. This research will elucidate the role of tooth/bone matrix material properties in oral and skeletal health and disease. Eventually, the proposed studies will facilitate the development of novel diagnostic tools and therapeutic treatments regarding dentin matrix malformations, skeletal abnormalities, and craniofacial dysplasias. PUBLIC HEALTH RELEVANCE: These studies will contribute to our knowledge of how bone and tooth formation occurs normally, and also has the potential for development of novel therapeutics regarding dentin remodeling, and individuals with genetic or non-hereditary skeletal and craniofacial dysplasias.

描述（由申请人提供）：Runx2 是骨骼发育的关键组成部分。全球敲除研究证明了 Runx2 作为骨骼和牙齿发育调节剂的作用。 Runx2缺失小鼠出生时完全缺乏矿化，并且牙胚在帽状晚期/钟状早期停滞。此外，已经表明 Runx2 是间充质祖细胞向成骨细胞、软骨细胞和成牙本质细胞谱系的定型所必需的。 Runx2基因突变会导致人类骨骼异常，例如锁骨颅骨发育不良，这是由Runx2单倍体不足引起的。这种疾病的特点是骨骼和颅面异常。因此，了解 Runx2 的具体功能对于临床应用具有巨大的潜力。研究 Runx2 的细胞和组织特异性功能及其在出生后发育中的作用的尝试尚未成功。转基因小鼠模型表现出显着的表型变异，与 Runx2 在正常发育中的作用的基本理解相矛盾。例如，在成骨细胞定型阶段后过表达 Runx2 的转基因研究报告了骨质减少，这表明 Runx2 在成骨后期充当抑制剂。然而，已知Runx2的基因表达在整个胚胎发育过程中增加，并且Runx2在出生后发育中保持高表达。我建议采用一种新型 Runx2 floxed 小鼠模型以细胞类型特异性方式完成 Runx2 删除。我们之前已确认这是 Runx2 基因消融的有效模型。对于细胞类型特异性基因删除，我将使用 2.3kb I 型胶原蛋白启动子来驱动 Cre 表达。使用这个模型，我将确定 Runx2 在骨骼形成中的成骨细胞中的具体功能，并确定其在牙齿形成的成牙本质细胞中的作用。此外，该小鼠模型的预期生存能力超过了主要的出生后发育年龄，这将为骨骼和牙科研究带来宝贵的进展。我们的假设是，Runx2 是维持成熟成骨细胞表型和出生后骨获得所必需的，并且 Runx2 在成牙本质细胞中的功能对于成牙本质细胞成熟以及适当的牙本质和牙齿形成至关重要。我将通过体内和离体方法通过两个具体目标来阐述这一假设：1）Runx2 对骨骼形成的成骨细胞特异性调节作用； 2) 成牙本质细胞成熟和牙齿形成所需的 Runx2。从这些研究中获得的信息将为理解正常和异常成骨和牙齿发育所涉及的分子机制奠定基础。这项研究将阐明牙齿/骨基质材料特性在口腔和骨骼健康和疾病中的作用。最终，拟议的研究将促进有关牙本质基质畸形、骨骼异常和颅面发育不良的新型诊断工具和治疗方法的开发。 公共健康相关性：这些研究将有助于我们了解骨骼和牙齿形成如何正常发生，并且还有可能开发有关牙本质重塑以及患有遗传性或非遗传性骨骼和颅面发育不良的个体的新疗法。