Molecular Genetics of Lyme Arthritis

项目概要/摘要 莱姆病是由蜱传播的螺旋体伯氏疏螺旋体引起的， 美国每年30万例。它与一系列不同严重程度的临床症状有关， 范围从局部皮肤损伤到播散性感染，包括继发性皮肤损伤，关节炎， 神经病和心脏炎很明显，宿主的遗传调节反应有助于宿主的免疫应答。 症状的严重程度。我们已经采取了正向遗传学方法来鉴定决定基因的等位基因。 严重关节炎C3 H小鼠和轻度关节炎C57 BL/6（B6）之间莱姆关节炎的差异 老鼠.该分析已经确定了几条染色体上的数量性状位点，包括Bbaa 1位点 在Chr 4上，其包括I型IFN基因簇。其中C3 H Bbaa 1 等位基因渗入到B6背景（B6. C3 H-Bbaa 1）中，证实了遗传元件的存在 在这个基因座中，通过表达IFNβ（一种I型IFN）调节关节炎。由于C3 H和B6 IFNβ基因 由于缺乏多态性，任何表达差异都必须由连锁的遗传元件调节。先进的， 间隔特异性重组同源系（ISRCL）缩小了与Bbaa 1相关的物理区域 到2.2 Mbp，并确定了细胞周期蛋白依赖性激酶抑制基因Cdkn 2a，作为一个候选调节因子， 干扰素β表达与莱姆关节炎严重程度的关系各种实验表明， Bbaa 1对IFNβ表达影响通过B表现出来。burgdorferi刺激骨髓细胞，但 关节炎的另外的下游介质需要关节组织的驻留细胞的独特激活。 独立研究将IFNβ的关节炎诱导活性表征为肌肉生长抑制素（MSTK）。妈妈很好 其特征在于调节骨骼肌发育，但也涉及慢性疾病， 炎症我们将利用B6.C3-Bbaa 1 ISRCL来表征 Cdkn 2a基因座调节髓样细胞中IFNβ的产生，反过来，下游IFN β表达的机制也是如此。 效应器MMPs调节莱姆关节炎的发展。我们提出了一个组合的血统特异性 基因表达分析、基因表达沉默、靶向KO小鼠的开发以及小基因敲除的应用。 分子抑制剂，以确定复杂的相互作用参与莱姆病关节炎的发展。我们 这些发现可能为I型IFN驱动的其他病理提供了深入了解，这也可能涉及意想不到的 涉及Cdkn 2a和MTSN的途径。

PROJECT SUMMARY / ABSTRACT Lyme disease is caused by the tick borne spirochete Borrelia burgdorferi and there are estimated to be 300,000 cases/year in the US. It is associated with a spectrum of clinical symptoms of varying severities, ranging from localized skin lesion to disseminated infection including secondary skin lesions, arthritis, neuropathies, and carditis. It is apparent that genetically regulated responses of the host contribute to the severity of symptoms. We have taken a forward genetics approach to identify allelic genes that determine the difference in Lyme arthritis between the severely arthritic C3H mouse and the mildly arthritic C57BL/6 (B6) mouse. This analysis has identified Quantitative Trait Loci on several chromosomes, including the Bbaa1 locus on Chr 4, which encompasses the Type I IFN gene cluster. Congenic mouse lines in which the C3H Bbaa1 allele was introgressed onto the B6 background (B6.C3H-Bbaa1) confirmed the presence of a genetic element in this locus that regulates arthritis through expression of IFNβ, a Type I IFN. As the C3H and B6 IFNβ genes lack polymorphisms, any expression differences must be regulated by a linked genetic element. Advanced, interval specific recombinant congenic lines (ISRCL) have narrowed the physical region associated with Bbaa1 to 2.2 Mbp and identified the Cyclin Dependent Kinase Inhibitory gene, Cdkn2a, as a candidate regulator of IFNβ expression and determinant of the severity of Lyme arthritis. A variety of experiments demonstrated that the Bbaa1 impact on IFNβ expression was manifest through B. burgdorferi stimulation of myeloid cells, but that an additional, downstream mediator of arthritis required distinct activation of resident cells of the joint tissues. Independent studies characterized the arthritis-inducing activity of IFNβ as myostatin (MSTN). MSTN is well characterize as modulating skeletal muscle development, but has also been implicated in chronic disease and inflammation. We will utilize the B6.C3-Bbaa1 ISRCLs to characterize the mechanism by which products of the Cdkn2a locus regulate IFNβ production in myeloid cells, and, in turn, the mechanism by which the downstream effector MSTN modulates Lyme arthritis development. We propose a combination of lineage-specific expression analysis, silencing of gene expression, development of targeted KO mice, and the use of small molecule inhibitors in order to define the complex interactions involved in Lyme arthritis development. Our findings may provide insight into other pathologies driven by Type I IFN, which could also implicate unexpected pathways involving Cdkn2a and MTSN.