Molecular and Cellular Pathogenesis of Cherubism

描述（由申请人提供）：“巨颌症”是一种人类常染色体显性遗传疾病，其特征为过度骨吸收和颌骨中炎性纤维组织积聚。我们确定了导致这种人类疾病的基因，一种称为“SH 3结构域结合蛋白2（SH 3BP 2）”的信号衔接蛋白，并确定了导致这种疾病的突变。为了进一步研究巨颌症的发病机制，我们已经产生了携带这种突变（小鼠中的P416 R）的敲入小鼠模型。与人类疾病相似，巨颌症小鼠表现出全身性巨噬细胞驱动的炎症，肿瘤坏死因子-α（TNF-1）产生增加，破骨细胞分化增强，导致严重的全身性炎性骨丢失。因此，这些小鼠是有用的，不仅作为一个模型的cherubism，但也有可能作为一个模型的其他炎症性骨疾病。 所提出的研究的总体假设是，在幼稚病相关的炎性骨病中，TNF-1的错误表达和失调是通过髓系细胞中的SH 3BP 2信号传导介导的。我们提出SH 3BP 2突变导致巨噬细胞和破骨细胞前体分别响应于巨噬细胞集落刺激因子（M-CSF）和核因子-κ B（NF-κ B）配体（RANKL）的受体激活剂的异常信号传导。我们还提出，过度活跃的巨噬细胞负责升高的TNF-1，其可以反馈以进一步激活破骨细胞，破骨细胞已经通过突变SH 3BP 2变得过度活跃。我们的初步数据表明，ERK和MyD 88参与了过度活跃的巨噬细胞产生TNF- 1，而Syk和NFATc 1参与了破骨细胞的过度活化。为了验证这些假设，提出了以下具体目标：1）确定SH 3BP 2调节巨噬细胞中TNF-1产生的机制，2）确定SH 3BP 2在NFATc 1介导的破骨细胞分化中的作用，3）确定MyD 88介导的信号通路在巨颌症炎症发病机制中的作用。将巨像症小鼠模型与其他小鼠模型（如SHP-1和MyD 88缺失小鼠）杂交，并结合相关的体外试验来测试这些假设。对SH 3BP 2和MyD 88介导的信号通路、TNF-1的产生及其在炎症和破骨细胞活化中的作用的详细分析将极大地有助于更好地理解巨颌症中的炎性骨病。确定这些途径的分子组成部分及其功能也将有助于开发其他炎症性疾病（如类风湿性关节炎和牙周病）治疗干预的新靶点。 公共卫生相关性：该项目的目标是确定与巨颌症相关的炎症性骨病中涉及的新分子途径。这些途径的成功鉴定将有助于设计更有效的药物，用于治疗患有巨颌症以及其他炎症性疾病（如类风湿性关节炎和牙周病）的患者。

DESCRIPTION (provided by applicant): "Cherubism" is a human autosomal dominant disorder characterized by excessive bone resorption and the accumulation of inflammatory fibrous tissue in the jaws. We identified the gene responsible for this human disease, a signaling adaptor protein called "SH3 domain binding protein 2 (SH3BP2)", and pinpointed the mutations responsible for this condition. To further investigate the pathogenesis of Cherubism, we have generated a knock-in mouse model carrying this mutation (P416R in mice). Similar to the human disease, the cherubism mice exhibit systemic macrophage-driven inflammation with increased tumor necrosis factor-alpha (TNF-1) production as well as enhanced osteoclast differentiation, resulting in severe systemic inflammatory bone loss. Therefore these mice are useful, not only as a model of cherubism, but also potentially as a model for other inflammatory bone diseases. The overall hypothesis for the proposed studies is that the misexpression and disregulation of TNF-1 in Cherubism-associated inflammatory bone disease is mediated through SH3BP2 signaling in myeloid lineage cells. We propose SH3BP2 mutations result in abnormal signaling in macrophages and osteoclast precursors in response to macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor-KB (NF-KB) ligand (RANKL), respectively. We also propose that the hyperactive macrophages are responsible for elevated TNF-1 which can feed back to further activate the osteoclasts, already made hyperactive through mutant SH3BP2. Our preliminary data suggest that ERK and MyD88 are involved in TNF- 1 production by hyperactive macrophages, while Syk and NFATc1 are involved in osteoclast hyperactivation. To test these hypotheses, the following specific aims are proposed: 1) Determine the mechanisms by which SH3BP2 regulates TNF-1 production in macrophages, 2) Determine the role of SH3BP2 in NFATc1-mediated osteoclast differentiation, and 3) Determine the role of the MyD88-mediated signaling pathway in the pathogenesis of inflammation in cherubism. The cherubism mouse model will be crossed with other mouse models such as the SHP-1 and MyD88 null mice in conjunction with relevant in vitro assays to test these hypotheses. Detailed analyses of the SH3BP2- and MyD88-mediated signaling pathway, the production of TNF-1 and their roles in inflammation and osteoclast activation will greatly contribute to better understanding of inflammatory bone disease in cherubism. Identifying the molecular components of these pathways and how they function will also aid in developing new targets for therapeutic intervention for other inflammatory diseases, such as rheumatoid arthritis and periodontal disease. PUBLIC HEALTH RELEVANCE: The goal of this project is to identify the novel molecular pathways involved in the inflammatory bone disease associated with Cherubism. Successful identification of these pathways will facilitate the design of more effective drugs for the treatment of patients suffering from Cherubism as well as other inflammatory diseases such as rheumatoid arthritis and periodontal disease.