Type III Collagen Gene Expression in Cartilage

描述(申请人提供)：鸡III型胶原基因产生两种不相关的蛋白质，III型胶原和一种小的非胶原蛋白Col3alt。该基因的上游启动子引导III型胶原mRNA和蛋白的产生，而内部启动子则指导产生Col3alt的另一种转录本的产生。该基因在软骨形成和软骨病理过程中表现出复杂的调控模式。I型胶原在软骨形成前间质细胞中产生，但在胚胎软骨中不存在。然而，III型胶原在成人关节软骨和椎间盘的软骨样结构中被发现。在骨关节炎和退行性间盘疾病中，III型胶原的含量显著增加，并在培养的软骨细胞中被白介素1诱导，白介素1是一种在骨关节炎中发挥重要作用的促炎细胞因子。Col3alt是III型胶原基因选择性转录本的产物，与III型胶原一起在软骨形成前间充质中产生；然而，Col3alt的产生继续在胚胎软骨和幼年生长板中进行，在那里它被分泌到基质中。将针对以下特定目标研究该基因的调控及其两个产物的功能：1)鉴定调控软骨形成过程中III型胶原停止产生的转录机制；2)确定III型胶原基因在软骨细胞中的表达是否在静水压力和促炎细胞因子的反应下重新激活，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；以及4)通过调节Col3alt在体外和体内肢体发育过程中的产生来检验软骨形成所需的Col3alt的假设。这些实验将加深我们对III型胶原基因在软骨形成过程中的调节和功能的理解，以及对应激和促炎细胞因子的响应，并将确定III型胶原在软骨和椎间盘中的作用以及Col3alt在软骨形成中的作用。最后，这些研究将为复杂基因的调控提供独特的见解，本质上，复杂基因是基因中的一个基因。

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.