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质，III型胶原蛋白和一种小的非胶原蛋白，Col 3alt。该基因的上游启动子指导III型胶原mRNA和蛋白质的产生，而内部启动子指导产生Col 3alt的替代转录物的产生。该基因在软骨形成和软骨病理学中表现出复杂的调控模式。III型胶原在软骨形成前的间充质细胞中产生，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的软骨样结构中。III型胶原的量在骨关节炎和退行性椎间盘疾病中显著增加，并且通过用白细胞介素1（一种在骨关节炎中起重要作用的促炎细胞因子）处理在培养的软骨细胞中诱导。Col 3 alt是III型胶原基因的替代转录产物，与III型胶原一起沿着于前软骨形成间充质中产生;然而，Col 3 alt的产生在胚胎软骨和幼年生长板中继续，在那里它被分泌到基质中。本研究的主要目的是：1）研究软骨形成过程中III型胶原基因表达的转录调控机制; 2）研究软骨细胞中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激活，并确定激活的机制; 3）确定III型胶原蛋白在软骨基质中的作用及其在椎间盘中的功能;以及4）通过在体外和体内肢体发育期间调节其产生来检验Col 3alt是软骨形成所需的假设。拟议的实验将加强我们的理解的调节和功能的III型胶原蛋白基因在软骨形成过程中，并响应于应力和促炎细胞因子，并将定义的角色III型胶原蛋白在软骨和椎间盘和功能的Col 3alt在软骨形成。最后，这些研究将为复杂基因座的调控提供独特的见解，复杂基因座本质上是基因中的基因。

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.