Consequences of Mutant COMP Expression and Therapeutic Approaches in Transgenic M

描述（由申请方提供）：两种骨骼发育不良，假性软骨发育不全（PRACH）和多发性骨骺发育不良（MED/EDM 1）是由于突变COMP（MT-COMP）在内质网（ER）中大量胞内滞留导致骨发育期间软骨细胞过早死亡。本研究的重点是确定MT- COMP促进软骨细胞病理学的细胞机制，并确定各种药物是否抑制或逆转病理学。在以前的研究中，我们已经证明：1）COMP中的突变引起骨骼发育不良，2）突变的COMP干扰COMP以及IX型胶原和基质蛋白-3蛋白向细胞外基质的输出，3）细胞内基质不适当地组装在巨大的rER脑池中，4）PSACH软骨基质缺乏ECM蛋白和5）COMP的细胞内滞留导致软骨细胞过早死亡。虽然我们的体外软骨细胞模型系统表明突变COMP不被细胞质量控制机制降解，但缺乏动物模型系统限制了确定导致MT-COMP产生的细胞病理学的分子机制的研究。我们已经建立了转基因小鼠模型，其中可诱导的软骨细胞特异性MT-COMP表达重现了PSACH软骨细胞病理学。该MT-COMP小鼠在体内显示出细胞内生长板病理学，并且软骨细胞可以被分离并用于体外研究。在这些研究中，我们将使用这种新颖独特的转基因小鼠，将我们的努力集中在：1）定义未折叠蛋白质应答（UPR）和细胞凋亡激活在体内响应软骨细胞中的MT-COMP保留的作用，2）测试不同药理学试剂对抑制或逆转MT-COMP的细胞内滞留的功效，和3）表征MT-COMP的作用。COMP对小鼠终身关节软骨形态和功能的影响。MT-COMP小鼠模型使我们能够测试从ER中去除MT-COMP将使软骨细胞恢复正常功能的假设。这是迈向治疗干预的第一步，这将是向前迈出的重要一步，因为目前只有对症治疗可用于与PSACH和MED相关的疼痛性骨关节炎。总之，这项工作的结果将提供重要的信息，最终将导致更好地护理PSACH，MED/EDM 1和骨关节炎患者。

DESCRIPTION (provided by applicant): Two skeletal dysplasias, pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (MED/EDM1) result from massive intracellular retention of mutant COMP (MT-COMP) in the endoplasmic reticulum (ER) which causes premature chondrocyte death during bone development. The focus of this research is to determine the cellular mechanism by which MT- COMP promotes the chondrocyte cellular pathology and to determine whether various pharmacologic agents inhibit or reverse the pathology. In previous studies, we have shown that: 1) mutations in COMP cause skeletal dysplasias, 2) mutant COMP interferes with the export of COMP as well as type IX collagen and matrilin-3 proteins to the extracellular matrix, 3) intracellular matrix is inappropriately assembled in giant rER cisternae, 4) the PSACH cartilage matrix is deficient in ECM proteins and 5) the intracellular retention of COMP causes premature chondrocyte cell death. While our in vitro chondrocyte model system indicates that mutant COMP is not degraded by the cellular quality control machinery, the lack of an animal model system has limited studies to define the molecular mechanisms that result in the cellular pathology created by MT-COMP. Importantly and critical for this proposal, we have created a transgenic mouse model in which inducible chondrocyte-specific MT-COMP expression recapitulates the PSACH chondrocyte pathology. This MT-COMP mouse shows intracellular growth plate pathology in vivo and the chondrocytes can be isolated and utilized for in vitro studies. In these studies, we will use this novel and unique transgenic mouse to focus our efforts on: 1) defining the role of the Unfolded Protein Response (UPR) and activation of apoptosis in response to MT-COMP retention in chondrocytes in vivo, 2) testing the efficacy of different pharmacologic agents on inhibiting or reversing the intracellular retention of MT-COMP and 3) characterizing the effect of MT-COMP on articular cartilage morphology and function in mice throughout life. The MT-COMP mouse model allows us to test the hypothesis that removal of MT-COMP from the ER will return the chondrocyte to normal functionality. This is a first step towards a therapeutic intervention which will be a significant step forward as only symptomatic treatment is currently available for the painful osteoarthritis that is associated with PSACH and MED. Altogether, the results of this work will provide important information that will ultimately lead to better care of individuals with PSACH, MED/EDM1 and osteoarthritis.