Type III Collagen Gene Expression in Cartilage

描述（由申请人提供）：鸡III型胶原蛋白基因产生两种不相关的蛋白，III型胶原蛋白和一种小的非胶原蛋白Col3alt。该基因的上游启动子指导III型胶原mRNA和蛋白质的产生，而内部启动子指导另一种转录物的产生，产生Col3alt。该基因在软骨形成和软骨病理过程中表现出复杂的调节模式。ii型胶原蛋白产生于软骨前间充质细胞，但不存在于胚胎软骨中。然而，III型胶原蛋白存在于成人关节软骨和椎间盘软骨样结构中。III型胶原的数量在骨关节炎和退行性椎间盘疾病中显著增加，并在培养的软骨细胞中通过白细胞介素1（一种在骨关节炎中起重要作用的促炎细胞因子）的治疗而诱导。Col3alt是III型胶原基因的替代转录产物，与III型胶原一起在软骨前间质中产生；然而，Col3alt在胚胎软骨和幼体生长板中继续产生，并分泌到基质中。该基因的调控及其两个产物的功能将在以下具体目标中进行研究：1)表征软骨形成过程中III型胶原蛋白生成停止的转录机制；2)确定软骨细胞中III型胶原基因表达是否在静水压力和促炎细胞因子的作用下被重新激活，并确定重新激活的机制；3)确定III型胶原在软骨基质中的作用及其在椎间盘中的功能；4)通过在体外和体内肢体发育过程中调节Col3alt的产生，检验Col3alt是软骨形成所必需的假设。本实验将加强我们对III型胶原基因在软骨形成过程中对应激和促炎细胞因子的调控和功能的理解，并将明确III型胶原在软骨和椎间盘中的作用以及Col3alt在软骨形成中的功能。最后，这些研究将为复杂基因座的调控提供独特的见解，而复杂基因座本质上是一个基因中的一个基因。

DESCRIPTION (provided by applicant): The chick type III collagen gene produces two unrelated proteins, type III collagen and a small non-collagenous protein, Col3alt. The upstream promoter of this gene directs production of type III collagen mRNA and protein, while an internal promoter directs production of an alternative transcript that produces Col3alt. This gene displays a complex pattern of regulation during chondrogenesis and in cartilage pathology. Type Ill collagen is produced in prechondrogenic mesenchymal cells, but is not present in embryonic cartilages. However, type III collagen is found in adult articular cartilages and in the cartilage-like structures of the intervertebral disk. The amount of type III collagen is increased significantly in osteoarthritis and degenerative disk disease, and is induced in cultured chondrocytes by treatment with interleukin 1, a pro-inflammatory cytokine that plays an important role in osteoarthritis. Col3alt, the product of the alternative transcript of the type III collagen gene, is produced in prechondrogenic mesenchyme along with type III collagen; however, production of Col3alt continues in embryonic cartilages and in juvenile growth plates, where it is secreted into the matrix. The regulation of this gene and the functions of its two products will be investigated in the following specific aims: 1) Characterize the transcriptional mechanisms regulating cessation of type III collagen production during chondrogenesis; 2) Determine whether type III collagen gene expression is reactivated in chondrocytes in response to hydrostatic pressure and proinflammatory cytokines and identify the mechanisms responsible for reactivation; 3) Determine the role of type III collagen in the cartilage matrix and its function in the intervertebral disc; and 4) Examine the hypothesis that Col3alt is required for chondrogenesis, by modulating its production during in vitro and in vivo limb development. The proposed experiments will strengthen our understanding of the regulation and function of the type III collagen gene during chondrogenesis and in response to stress and proinflammatory cytokines, and will define the roles of type III collagen in cartilage and intervertebral disc and the function of Col3alt in chondrogenesis. Finally, these studies will provide unique insights into the regulation of a complex locus which is, in essence, a gene within a gene.