MUTANT p62 AND THE ROLE OF THE BONE MICROENVIRONMENT IN PAGET'S DISEASE

描述（由申请人提供）：佩吉特病（PD）是一种慢性骨病，其特征是局灶区骨重塑高度夸张和紊乱。PD的病因一直难以确定，因为很明显，遗传和环境因素都对该疾病有影响。最近，在家族性和散发性PD病例中发现了SQSTM1/p62基因的疾病相关突变，该基因的突变可能与多达30%的Paget病例有关。SQSTM1/p62基因编码一个62 kDa的蛋白，该蛋白在正常破骨细胞发生的多种信号转导途径中起作用，包括由RANKL、TNF和IL-1激活的信号转导途径。我们假设p62突变导致破骨细胞前体中一种或多种途径的激活增加，从而导致破骨细胞生成增加和对PD后续发展的易感性。我们进一步假设，在成骨细胞或骨髓基质细胞中表达突变体p62，可以增强它们支持破骨细胞发生的能力，并增加新骨形成，以响应破骨细胞活性的增加。为了研究这些假设，我们通过在内源性小鼠p62基因中引入P394L突变（类似于人类Paget相关的P392L突变），建立了p62突变的Paget患者小鼠模型。我们现在提出了一系列互补的体内和体外实验，利用这种新开发的小鼠模型来确定这种突变在多大程度上促成了完整的遗传表型，并确定这种突变对调节破骨细胞和成骨细胞形成、功能和存活的信号通路的影响。这种独特的小鼠模型将使我们能够确定p62突变促进PD发展的具体机制，并将作为确定其他环境和遗传因素对PD的影响的有价值的研究工具。公共卫生相关性：帕金森病是仅次于骨质疏松症的第二大常见骨骼疾病，Paget患者会出现明显的疼痛、畸形、骨折易感性增加和各种神经系统并发症。然而，尽管帕金森病很普遍，但对其的研究相对不足，对其起源的了解也很少。提出的研究应该导致更好地了解PD，并因此可能促进改进治疗方法的发展。

DESCRIPTION (provided by applicant): Paget's disease (PD) is a chronic bone disease characterized by focal regions of highly exaggerated and disordered bone remodeling. The etiology of PD has been difficult to define, as there are clearly both genetic and environmental contributions to the disease. Recently, disease-associated mutations have been identified in the SQSTM1/p62 gene in cases of both familial and sporadic PD, and mutations of this gene may be linked to up to 30% of all Paget's cases. The SQSTM1/p62 gene encodes a 62 kDa protein that functions in multiple signal transduction pathways involved in normal osteoclastogenesis, including those activated by RANKL, TNF, and IL-1. We hypothesize that p62 mutations lead to increased activation of one or more of these pathways in osteoclast precursors, resulting in increased osteoclastogenesis and susceptibility to the subsequent development of PD. We further hypothesize that expression of mutant p62 in osteoblasts or bone marrow stromal cells enhances their capacity to support osteoclastogenesis as well as increase new bone formation in response to the increased osteoclast activity. To investigate these hypotheses, we have developed a mouse model of Paget's patients with p62 mutations by introducing a P394L mutation (analogous to the human Paget's-associated P392L mutation) into the endogenous mouse p62 gene. We now propose a series of complementary in vivo and in vitro experiments employing this newly developed mouse model to determine the extent to which this mutation contributes to the full pagetic phenotype, and to determine the effect of this mutation on the signaling pathways that regulate both osteoclast and osteoblast formation, function, and survival. This unique mouse model will allow us to determine the specific mechanisms by which p62 mutation contributes to the development of PD, and will also serve as a valuable research tool for identifying other environmental and genetic factors contributing to PD. PUBLIC HEALTH RELEVANCE: PD is the second most common bone disease after osteoporosis, and results in significant pain, deformity, increased susceptibility to fractures, and a variety of neurological complications in Paget's patients. However, despite the prevalence of PD, it is relatively understudied and its origin is poorly understood. The proposed studies should lead to a better understanding of PD, and may therefore facilitate the development of improved therapeutic approaches.