Strategy for Therapy of the Pseudoachondroplasia (PSACH) Phenotype: Understanding

软骨寡聚基质蛋白（COMP）的突变导致两种骨骼发育不良， 假性软骨发育不全（PSACH）和多发性骨骺发育不良（MED/EDM 1）， 与慢性关节异常有关本研究的重点是确定 是否由软骨突变的显性负效应引起的细胞病理学 寡聚基质蛋白（COMP）可以逆转。在我们之前的工作中，我们已经证明了 COMP的突变阻碍了蛋白质折叠所需的钙结合。不当 折叠的突变COMP与IX型胶原、基质蛋白-3一起保留在扩大的rER池中，沿着 和许多伴侣蛋白。这种保留具有下游效应， 缺乏这些蛋白质的细胞外基质，是一种严重紊乱的基质， 软骨细胞死亡相反，COMP无效小鼠是正常的，表明COMP不是 是软骨和骨骼发育和体内平衡所必需的。我们假设移除 的突变COMP将逆转和建立PRACH细胞表型， 软骨细胞功能和正常基质形成。为了验证这个假设，我们现在将 通过使用诱导型启动子来确定病理的时间途径及其解决方案 系统我们已经成功地在三维培养系统中过表达突变COMP， 概括了正常人软骨细胞中的疾病病理学。四环素（泰特） 诱导型启动子和表达TET激活的转录因子（rtTA）的DMA将用于诱导细胞表型和抑制突变体COMP的产生。 实验将在人原代生长板软骨细胞和转基因细胞中进行。 小鼠这些研究将使我们能够确定表型发展的时间， 表型是可逆的，这是朝着开发治疗方法迈出的重要一步 对这些使人衰弱的整形外科侏儒症进行干预。

Mutations in cartilage oligomeric matrix protein (COMP) cause two skeletal dysplasias, pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (MED/EDM1) both of which are associated with chronic joint abnormalities. The focus of this research is to determine whether the cellular pathology caused by the dominant negative effects of mutations in cartilage oligomeric matrix protein (COMP) can be reversed. In our previous work, we have demonstrated that mutations in COMP impede calcium-binding which is required for protein folding. Improperly folded mutant COMP is retained in enlarged rERcisternae along with type IX collagen, matrillin-3 and numerous chaperone proteins. This retention has the downstream effect of causing an extracellular matrix that is deficient in these proteins, a grossly disorganized matrix and eventual chondrocyte death. In contrast COMP null mice are normal suggesting that COMP is not necessary for cartilage and bone development and homeostasis. We hypothesize that removal of mutant COMP will reverse and established PSACH cellular phenotype and restore chondrocyte function and normal matrix formation. To test this hypothesis, we will now define the temporal pathway of the pathology and its resolution by using an inducible promoter system. We have successfully over-expressed mutant COMP in a 3-D culture system to recapitulate the disease pathology in normal human chondrocytes. The tetracycline (TET) inducible promoter and DMA expressing the TET-activated transcription factor (rtTA) will be used to both induce the cellular phenotype and to repress the production of mutant COMP. These experiments will be conducted in human primary growth plate chondrocytes and in transgenic mice. These studies will allow us to determine the timing of phenotype development and whether the phenotype is reversible, which is an important step towards toward developing a treatment intervention for these debilitating orthopedic dwarfing conditions.