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的成年人群。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揭示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，并描述了许多导致SEDL表型的突变-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所起的作用，提出了以下目标：1）确定sedlin的生化结构和性质，2）确定sedlin的亚细胞定位及其在整个鼠软骨形成中的表达模式，3）确定sedlin与之相关的蛋白质，4）建立SEDL的动物模型，和5）测试与sedlin相关的蛋白质的基因作为候选骨关节炎易感基因。为了实现这些目标，我们建议1）在体外表达天然sedlin并通过NMR光谱和X射线晶体学研究其结构，2）通过亚细胞分级、Western印迹和免疫电镜确定其亚细胞定位;跟踪其在鼠软骨形成过程中的表达，3）通过免疫沉淀鉴定sedlin相关蛋白并发现其基因中的多态性，4）产生SEDL基因座的敲除小鼠，并检查它们从胚胎到衰老的组织学表型，和5）在患有特发性骨关节炎的病例对照组群中测试（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患者的治疗方式提供线索。此外，我们预计这些研究将产生有价值的深入了解sedlin通路在维持软骨完整性和骨关节炎紊乱中的作用。

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.