Molecular Genetics of Lyme Arthritis

项目摘要/摘要 莱姆病是由壁虱传播的伯氏疏螺旋体引起的，据估计有 在美国，每年有30万例。它与一系列不同严重程度的临床症状有关， 范围从局限性皮肤损害到播散性感染，包括继发性皮肤损害，关节炎， 神经病和心脏炎。很明显，寄主的基因调控反应有助于 症状的严重程度。我们采取了一种向前遗传学的方法来确定决定基因的等位基因 重度关节炎C3H小鼠与轻度关节炎C57BL/6(B6)小鼠莱姆关节炎的差异 老鼠。这项分析已经确定了几个染色体上的数量性状基因座，包括Bbaa1基因座 在Chr 4上，它包含I型干扰素基因簇。C3HBbaa1的同源小鼠品系 等位基因被引入到B6背景(B6.C3H-Bbaa1)证实了遗传元件的存在 在这个基因中，通过表达干扰素β来调节关节炎，干扰素是一种I型干扰素。作为C3H型和B6型干扰素β基因 缺乏多态，任何表达差异都必须受到连锁遗传元件的调控。高级， 区间特异性重组同源基因系(ISRCL)缩小了与Bbaa1相关的物理区域 到2.2Mbp，并鉴定了Cyclin依赖的激酶抑制基因CDKn2a是一种候选的调控基因 干扰素β表达与莱姆关节炎严重程度的关系各种实验证明， BbaA1对干扰素β表达的影响是通过伯氏杆菌刺激髓系细胞而表现出来的，但 关节炎的另一个下游介体需要关节组织中驻留细胞的明显激活。 独立研究将干扰素β的关节炎诱导活性定性为肌肉生长抑素(MSTN)。MSTN状态良好 以调节骨骼肌发育为特征，但也与慢性疾病和 发炎。我们将利用B6.C3-Bbaa1 ISRCL来表征 CDKN2a基因座调控髓系细胞干扰素β的产生，进而调节其下游信号转导的机制。 效应器MSTN调节莱姆关节炎的发展。我们建议结合特定于世系的 表达分析、基因表达沉默、靶向KO小鼠的发展以及小鼠的使用 分子抑制剂，以确定莱姆关节炎发生过程中涉及的复杂相互作用。我们的 这些发现可能会为I型干扰素驱动的其他病理机制提供洞察，这也可能涉及意想不到的 涉及CDKN2a和MTSN的通路。

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.