MI--SIGNAL RESPONSIVE TRANSCRIPTION IN OSTEOCLASTS

MI--破骨细胞中的信号响应转录

• 批准号: 6171175
• 负责人: DAVID E FISHER
• 金额: $ 28.39万
• 依托单位: DANA-FARBER CANCER INST
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-06-01 至 2003-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6171175
• 关键词: bone marrow; connective tissue development; cytokine; dimer; genetic promoter element; genetic regulation; genetic transcription; human tissue; laboratory mouse; osteoclasts; osteopetrosis; transcription factor; transfection /expression vector

The Microphthalmia (Mi) gene encodes one of the oldest recognized factors critical to osteoclast development and function. Mi is also required for development of the melanocyte lineage. The recently cloned Mi gene encodes a HLH-ZIP transcription factor, and is unique in its highly restricted tissue distribution. We have defined protein and DNA interactions of MI and found it to bind and potentially activate transcription off promoters containing its recognition element. We have recently examined an unusual rat mutant which displays severe osteoporosis which resolves with aging and shown that this results from a large deletion within Mi. We also discovered 3 dimerization partners of Mi (TFEB, TFEC, and TFE3) collectively called the "MiT" family. At least one of these other factors is present in the Mi-deficient osteoclasts of this rat strain, suggesting a general a general role of this family in osteoclast function and maturation. Our studies in melanocytes have also revealed that Mi is strongly activated by MAP kinase phosphorylation following cytokine stimulation. c-Kit signaling operates through activation of Mi in this fashion. We now also know that the mechanism of this activation is phospho-Mi selective recruitment of the transcriptional co-activators p300/CBP. Importantly, our current results suggest that Mi is similarly phosphorylated in response to cytokine signaling in osteoclasts, and this response (to factors such as interleukin 6 and M-CSF) could lie critically within a major pathway of osteoclast activation. The understanding of such pathways is clearly central to future goals of modulating osteoclast function in conditions such as osteoporosis. To further enhance our understanding of this factor and extend our analysis of its actions within osteoclasts, this grant proposes to: 1) systematically examine Mi'T protein temporal expression patterns in osteoclasts throughout development and aging, 2) derive viral vectors permitting up- or down-regulation of endogenous MiT factors in osteoclasts, and examine their consequences on osteoclast development and function, 3) define mechanistic relationships between Mi and osteoclast signaling pathways of importance in bone homeostasis including other genes implicated in osteopetrosis and cytokines of functional importance, and 4) identify transcriptional target genes for Mi in osteoclasts by testing "rational" candidates identified through sequence analysis of known promoters as well as a highly stringent differential display which requires up-regulation by wild type Mi, down- regulation by dominant negative Mi, as well as cytokine-mediated Mi induction in the presence of cycloheximide. Through these studies we hope to gain insight into osteoclast biology through an understanding of Mi's central role.

小眼症(Mi)基因编码最古老的已知基因之一 破骨细胞发育和功能的关键因素。Mi也是 黑素细胞谱系发育所必需的。最近克隆的 MI基因编码一种hlh-ZIP转录因子，在其 组织分布高度受限。我们已经定义了蛋白质和DNA MI的相互作用，并发现它结合并潜在地激活 转录出含有其识别元件的启动子。我们有 最近检查了一种不寻常的老鼠突变体，它表现出严重的 骨质疏松症随着年龄的增长而解决，并表明这是由 小米体内的一个大的缺失。我们还发现了3个二聚体伙伴 Mi(TFEB、TFEC和TFE3)的成员统称为“MIT”家族。在… 这些其他因素中至少有一个存在于Mi缺乏症患者 这种大鼠品系的破骨细胞，表明了一般的作用 这个家族在破骨细胞的功能和成熟方面。我们在中国的学习 黑素细胞也显示Mi被MAP强烈激活 细胞因子刺激后的激酶磷酸化。C-套件信令 以这种方式通过激活Mi来运行。我们现在也知道， 这种激活的机制是磷酸-Mi选择性地招募 转录共激活因子p300/CBP。重要的是，我们目前 结果表明，Mi类似地被磷酸化以响应 破骨细胞中的细胞因子信号，以及这种反应(对因素，如 如白介素6和M-CSF)可能处于关键的主要途径中 破骨细胞的激活。对这种途径的理解是清楚的 在条件下调节破骨细胞功能的未来目标的中心 比如骨质疏松症。进一步提高对此的认识 因素并扩展我们对其在破骨细胞中的作用的分析，这 格兰特建议：1)系统地研究Mi‘t蛋白质的时间 破骨细胞在发育和衰老过程中的表达模式 衍生允许上调或下调内源性MIT的病毒载体 破骨细胞中的因子及其对破骨细胞的影响 发展和功能，3)定义小鼠之间的机械关系 破骨细胞信号通路在骨稳态中的重要作用 包括与骨质疏松症有关的其他基因和 功能重要性，以及4)确定转录靶基因 MI在破骨细胞中通过测试通过 已知启动子的序列分析以及高度严格的 差异显示需要野生型Mi上调，下调- 显性负性Mi和细胞因子介导的Mi的调节 在环己酰亚胺存在下的诱导。通过这些研究，我们 希望通过对破骨细胞生物学的了解了解破骨细胞生物学 军情六处的核心角色。