Molecular and Cellular Pathogenesis of Cherubism

描述(申请人提供)：“切尔鲁比症”是一种人类常染色体显性遗传病，其特征是过度的骨吸收和颌骨中炎性纤维组织的积聚。我们确定了导致这种人类疾病的基因，一种名为SH3结构域结合蛋白2(SH3BP2)的信号适配蛋白，并精确定位了导致这种疾病的突变。为了进一步研究切尔鲁贝氏症的发病机制，我们建立了一个携带这种突变的敲入小鼠模型(小鼠中的P416R)。与人类疾病相似，小鼠出现全身性巨噬细胞驱动的炎症，肿瘤坏死因子-1的产生增加，破骨细胞分化增强，导致严重的全身性炎症性骨丢失。因此，这些小鼠是有用的，不仅是作为天使症的模型，而且还可能作为其他炎症性骨病的模型。这些研究的总体假设是，在切尔贝氏症相关的炎症性骨病中，肿瘤坏死因子-1的错误表达和失调是通过髓系细胞中的SH3BP2信号介导的。我们认为SH3BP2突变分别导致巨噬细胞和破骨细胞前体细胞对巨噬细胞集落刺激因子(M-CSF)和核因子-KB受体激活剂配体(RANKL)的应答信号异常。我们还提出，过度活跃的巨噬细胞负责升高的肿瘤坏死因子-1，而肿瘤坏死因子-1可以反馈进一步激活已经通过突变的SH3BP2而变得过度活跃的破骨细胞。我们的初步数据表明，ERK和MyD88参与了高活性巨噬细胞产生肿瘤坏死因子-1，而Syk和NFATc1参与了破骨细胞的高激活。为了验证这些假说，我们提出了以下具体目标：1)确定SH3BP2调节巨噬细胞产生肿瘤坏死因子-1的机制；2)确定SH3BP2在NFATc1介导的破骨细胞分化中的作用；3)确定MyD88介导的信号通路在巨噬细胞炎症发病机制中的作用。该小鼠模型将与其他小鼠模型(如SHP-1和MyD88缺失小鼠)杂交，并结合相关的体外试验来验证这些假说。详细分析SH3BP2和MyD88介导的信号通路、肿瘤坏死因子-1的产生及其在炎症和破骨细胞激活中的作用，将有助于更好地理解大猩猩的炎症性骨病。确定这些途径的分子组成和它们的功能也将有助于为其他炎症性疾病的治疗干预开发新的靶点，如类风湿性关节炎和牙周病。

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.