Role of a TGF-B Regulated Gene in Human and Mouse Osteoblasts and Skeleton

TGF-B 调控基因在人和小鼠成骨细胞和骨骼中的作用

• 批准号: 8073169
• 负责人: THOMAS C SPELSBERG
• 金额: $ 32.08万
• 依托单位: MAYO CLINIC ROCHESTER
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-01 至 2012-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8073169
• 关键词: Alkaline Phosphatase; Animals; Biological; Bone Diseases; Bone Tissue; Bone remodeling; Calvaria; Cells; Data; Defect; Estrogen Receptors; Estrogens; Family; Female; Funding; Gender; Genes; Genetic Transcription; Gonadal Steroid Hormones; Growth; Hormone replacement therapy; Human; Investigation; Knockout Mice; Label; Laboratories; Maintenance; Mediating; Minerals; Molecular; Mus; Orchiectomy; Osteoblasts; Osteogenesis; Osteoporosis; Ovariectomy; Pathway interactions; Phenotype; Play; Protein Isoforms; Proteins; Regulation; Relative (related person); Reporting; Role; Signal Transduction; Skeletal Development; Skeleton; Stanolone; Surface; Testing; Work; base; bone; gene repression; insight; male; member; mineralization; mouse model; novel; osteoblast differentiation; osteoclastogenesis; skeletal; transcription factor

DESCRIPTION (provided by applicant): Estrogen (E2) and TGFb play pivotal roles in skeletal growth, osteoblast (OB) differentiation, and bone diseases such as osteoporosis. In spite of their role in OB differentiation and bone remodeling, the molecular mechanisms of E2 and TGFb action in bone tissue are not fully understood. During this laboratory's investigations of E2 and TGFb actions in OBs, we discovered and characterized the novel TGFb Inducible Early Gene-1 (TIEG) as a member of the Kruppel family of transcription factors (KLF-10). TIEG expression in OBs was shown to be induced by E2, TGFb, and BMPs. During the past funding period, we identified an important role for TIEG in mediating TGFb siganling as it represses Smad 7 expression and induces the expression of Smad 2. In order to better understand the function of TIEG in bone, we have generated TIEG-null (TIEG-/-) mice and have found that females, but not males, have smaller and weaker bones, characterized as osteopenic, relative to wild-type littermates. We have reported that calvarial OBs isolated from TIEG-/- mice have a markedly reduced capacity to mineralize bone and to support osteoclastogenesis. Further characterization of these OBs revealed decreased expression levels of Runx2, osterix, alkaline phosphatase, and other important OB marker genes. Recently, we have demonstrated that TIEG is capable of directly regulating the transcription of Runx2 and that Runx2 appears to be, at least in part, responsible for the observed defects in TIEG-/- OB mineralization. Our preliminary studies have shown that E2 induces the expression of TIEG in an estrogen receptor (ER) isoform specific manner. Finally, E2 also induces the expression of Runx2 in wild-type OBs, but not in TIEG-/- OBs, suggesting an important role for TIEG in mediating E2 action in bone. Based on these data, it is our hypothesis that the E2 regulation of TIEG, and the subsequent TIEG regulation of Runx2, is at least in part responsible for the observed defects in OBs which, in turn, leads to a gender-specific osteopenic phenotype in TIEG-/- mice. In order to test this hypothesis, we plan to determine: 1) the role that TIEG regulation of Runx2 expression has on the observed defects in TIEG-/- OBs, 2) the contribution of E2 regulation of TIEG expression to the TIEG-/- OB phenotype, 3) the role of TIEG in mediating E2 activation of Runx2 expression in OBs, and 4) the effects of gonadectomy of male and female TIEG-/- mice on the skeletal phenotype. The completion of these studies will help determine the biological role of TIEG in OB functions as well as skeletal development and maintenance. In addition, these studies will provide new insights into the mechanisms of E2 and TIEG regulation of Runx2 expression and their contribution to bone disease, including osteoporosis.

描述（申请人提供）：雌激素（E2）和TGFb在骨骼生长、成骨细胞（OB）分化和骨质疏松等骨疾病中发挥着关键作用。尽管 E2 和 TGFb 在 OB 分化和骨重塑中发挥作用，但 E2 和 TGFb 在骨组织中作用的分子机制尚不完全清楚。在本实验室研究 E2 和 TGFb 在 OB 中的作用期间，我们发现并表征了新型 TGFb 诱导早期基因 1 (TIEG)，它是 Kruppel 转录因子家族 (KLF-10) 的成员。 OB 中的 TIEG 表达被 E2、TGFb 和 BMP 诱导。在过去的资助期间，我们确定了 TIEG 在介导 TGFb 信号传导中的重要作用，因为它抑制 Smad 7 表达并诱导 Smad 2 表达。为了更好地了解 TIEG 在骨骼中的功能，我们培育了 TIEG 无效 (TIEG-/-) 小鼠，并发现雌性（而非雄性）具有较小且较弱的骨骼，相对于野生型而言，其特征为骨质减少 同窝的。我们报道，从 TIEG-/- 小鼠中分离出的颅骨 OB 矿化骨和支持破骨细胞生成的能力显着降低。这些 OB 的进一步表征揭示了 Runx2、osterix、碱性磷酸酶和其他重要 OB 标记基因的表达水平降低。最近，我们证明 TIEG 能够直接调节 Runx2 的转录，并且 Runx2 似乎至少部分负责观察到的 TIEG-/- OB 矿化缺陷。我们的初步研究表明，E2 以雌激素受体 (ER) 亚型特异性方式诱导 TIEG 的表达。最后，E2 还在野生型 OB 中诱导 Runx2 的表达，但在 TIEG-/- OB 中则不然，这表明 TIEG 在介导 E2 在骨中的作用中发挥着重要作用。基于这些数据，我们假设 E2 对 TIEG 的调节以及随后 TIEG 对 Runx2 的调节至少部分地导致了 OB 中观察到的缺陷，进而导致 TIEG-/- 小鼠出现性别特异性骨质减少表型。为了检验这一假设，我们计划确定：1) Runx2 表达的 TIEG 调节对 TIEG-/- OB 中观察到的缺陷的作用，2) TIEG 表达的 E2 调节对 TIEG-/- OB 表型的贡献，3) TIEG 在介导 OB 中 Runx2 表达的 E2 激活中的作用，以及 4) 男性和女性性腺切除术的影响TIEG-/- 小鼠 骨骼表型。这些研究的完成将有助于确定 TIEG 在 OB 功能以及骨骼发育和维护中的生物学作用。此外，这些研究将为 E2 和 TIEG 调节 Runx2 表达的机制及其对骨质疏松症等骨疾病的贡献提供新的见解。