MOLECULAR MECHANISMS FOR KELOID FORMATION

本研究的长期目标是了解纤维化疾病中真皮组织新生的分子机制。为了实现这一目标，我们开始研究遗传性瘢痕疙瘩的形成。瘢痕疙瘩是皮肤或角膜的良性肿瘤，是由异常伤口修复过程中成纤维细胞克隆性过度活跃引起的。相对大量的瘢痕疙瘩形成的家族病例使得有可能提出一种遗传方法来鉴定负责增加细胞增殖和细胞外基质表达的基因。我们对一个患有常染色体显性遗传性瘢痕疙瘩形成的大家族进行了连锁分析，利用覆盖整个基因组的多态微卫星标记来确定该疾病基因的染色体位点。我们已经确定了一个可能的疾病基因位点，现在正在通过包括其他显示位点同质性的家系来建立瘢痕疙瘩位点的高分辨率图谱。理想情况下，间隔应限制在1-2厘米以内。瘢痕疙瘩基因可通过候选基因克隆、位置候选基因克隆或位置克隆进行鉴定。我们将使用覆盖该区间的YAC和cosmid克隆构建瘢痕疙瘩轨迹的物理地图。一旦通过突变分析和与受影响表型的共分离确定了疾病基因，就计划进行研究，以表征蛋白质产物及其与其他基因或基因产物的相互作用。根据瘢痕疙瘩基因的性质，我们将计划在体外进行成纤维细胞和器官培养的研究，以及通过同源重组（敲入）表达突变基因的小鼠模型。这些研究应该使我们能够对涉及瘢痕疙瘩纤维化的下游事件进行进一步的研究。鉴定和表征瘢痕疙瘩基因产物，以及鉴定与其相互作用的其他蛋白质或基因，将有助于我们了解异常成纤维细胞的调节。我们认为瘢痕疙瘩是研究伤口愈合和纤维化过程中成纤维细胞活化和细胞外基质表达调控的良好模型。

The long-term goal of this study is to understand the molecular mechanisms of neoformation of dermal tissue in fibrotic diseases. To achieve this goal we began to study hereditary keloid formation. Keloids are benign tumors of the skin or cornea caused by clonal overactivity of fibroblasts during abnormal wound repair. The relatively large number of familial cases of keloid formation makes it possible to propose a genetic approach for the identification of a gene responsible for increased cell proliferation and extracellular matrix expression. We performed linkage analysis of one large family afflicted with an autosomal dominant form of hereditary keloid formation to identify the chromosomal locus of the disease gene by using polymorphic microsatellite markers covering the entire genome. We have identified a possible disease gene locus and are now in the process of establishing a high resolution map of the keloid locus by including other pedigrees that show locus homogeneity. Ideally, the interval will be restricted to less than 1-2 cM. The keloid gene will be identified by candidate gene cloning, positional candidate gene cloning, or positional cloning. We will construct a physical map of the keloid locus using YAC and cosmid clones covering this interval. Once the disease gene has been identified by mutation analysis and by co-segregation with the affected phenotype, studies are planned to characterize the protein product and its interactions with other genes or gene products. Depending on the nature of the keloid gene, we will plan in vitro studies of fibroblast and organ cultures as well as a mouse model that expresses the mutated gene by homologous recombination (knock-in). These studies should enable us to perform further studies on down-stream events, which are involved in the fibrosis of keloid scars. Identifying and characterizing the keloid gene product, and identifying other proteins or genes with which it interacts, will help us understand abnormal fibroblast regulation. We suggest that keloids are an excellent model for studying regulation of fibroblast activation and extracellular matrix expression during wound healing and fibrosis.