The Role of Sedlin in Maintaining Cartilage Integrity

描述（由申请人提供）：骨关节炎是一种慢性衰弱性疾病，影响多达1/3的成年人。越来越多的证据表明，遗传因素影响其发展，更好地了解遗传性软骨发育不良无疑将阐明所有退行性关节疾病的共同过程。迟发性脊椎骨骺发育不良（SEDL）是一种软骨发育不良，其特征是不成比例的身材矮小、x连锁遗传和早发性骨关节炎。我们最近已经确定了导致这种疾病的基因，并描述了导致SEDL表型的许多突变——然而，SEDL基因产物“sedlin”的功能仍有待阐明。为了确定sedlin蛋白在维持软骨完整性中的作用，我们提出了以下目标：1)确定sedlin的生化结构和性质，2)确定sedlin在小鼠软骨形成过程中的亚细胞定位及其表达模式，3)确定sedlin相关蛋白，4)建立SEDL动物模型，5)检测sedlin相关蛋白基因作为骨关节炎候选易感基因。为了实现这些目标，我们提出：1)在体外表达天然赛德林，并通过核磁共振光谱和x射线晶体学研究其结构；2)利用亚细胞分离、免疫印迹和免疫电镜确定其亚细胞定位；3)通过免疫沉淀法鉴定sedlin相关蛋白并发现其基因多态性，4)创建SEDL基因座敲除小鼠并检测其从胚胎到衰老的组织学表型，以及5)在特发性骨关节炎病例对照队列中测试(3)中鉴定的基因作为骨关节炎易感性的候选基因。阐明SEDL基因的表达模式和功能可能为设计SEDL患者的治疗方案提供线索。此外，我们预计这些研究将对sedlin通路在维持骨关节炎软骨完整性及其紊乱中的作用产生有价值的见解。

DESCRIPTION (provided by applicant): Osteoarthritis is a chronic debilitating disease that affects up to 1/3 of the adult population. Growing evidence suggests that genetic factors influence its development, and a better understanding of inherited chondrodysplasias will undoubtedly shed light on the processes common to all degenerative joint disease. Spondyloepiphyseal dysplasia tarda (SEDL) is a chondrodysplasia that is characterized by disproportionate short stature, X-linked inheritance, and early-onset osteoarthritis. We have recently identified the gene responsible for this disorder, and have characterized numerous mutations responsible for the SEDL phenotype--However, the function of the SEDL gene product, "sedlin," remains to be elucidated. In order to determine the role played by the sedlin protein in maintaining cartilage integrity, the following goals are proposed: 1) to determine the biochemical structure and properties of sedlin, 2) to determine the subcellular localization of sedlin and its expression pattern throughout murine chondrogenesis, 3) to determine the proteins with which sedlin associates, 4) to establish an animal model for SEDL, and 5) to test the genes of proteins associated with sedlin as candidate osteciarthritis susceptibility genes. To fulfill these aims, we propose to 1) express native sedlin in vitro and study its structure by NMR spectroscopy and X-ray crystallography, 2) determine its subcellular localization using subcellular fractionation, Western blotting, and immunoelectron microscopy; follow its expression during murine chondrogenesis, 3) identify sedlin-associated proteins by immunoprecipitation and find polymorphisms in their genes, 4) create knockout mice for the SEDL locus and examine their histologic phenotype from embryo through senescence, and 5) test the genes identified in (3) as candidate genes for osteoarthritis susceptibility within a case-control cohort with idiopathic osteoarthritis. Elucidation of the expression pattern and function of the SEDL gene may provide clues for designing therapeutic modalities for individuals affected with SEDL. Moreover, we anticipate that these studies will yield valuable insight into the role of the sedlin pathway in maintaining cartilage integrity and its derangement in osteoarthritis.