Duck Antibody Genes: Unusual Organization and Expression

拟议研究的长期目标是了解控制糖尿病的遗传机制。 鸭免疫球蛋白基因的表达。这只鸭子的免疫反应可以被描述为 无效，考虑到鸭子(和其他水禽)作为载体的作用，这对人类健康具有重要意义 (或蓄水池)对人类有传染性的疾病。例如，鸭子是全年唯一的鸟类储藏库 甲型流感病毒，这是导致新型流感出现的基因变异的来源 对人类有致病性的菌株。了解鸭抗体表达的分子基础将 允许了解他们无效的抗体反应，并对我们的 了解转录控制的进化，这是比较基因组学的一个重要方面。这个 鸭有一个不同寻常的免疫球蛋白重链(IgH)基因座，该基因在其 生殖系组织。3个恒定的(C)区基因排列为Mu-Alpha-upsilon，与Alpha基因 在反向转录方向上。这导致了与转录控制相关的独特问题 尤其是类切换重组的控制。这些都在本报告的具体目标中进行了阐述 建议，而要检验的假设可以用三个问题来表述：1)α基因有没有它的 自己的i-外显子还是依赖双向的i-upsilon启动子来启动类向IgA的切换？2)有 通过I-外显子启动子转录控制Ig类转换的信号转导通路 在脊椎动物进化中保守吗？3)哺乳动物免疫球蛋白基因座在两个基因中都含有转录增强子 C基因簇的Jh~Mu内含子和3‘端。在鸭的免疫球蛋白基因中，增强子在哪里？ 它们包含转录因子结合基序吗？它们是如何发挥作用的？该方法涉及到 通过功能分析识别转录调控元件(即它们驱动转录的能力 报告基因)，以及I-外显子启动子对细胞因子诱导的类别转换信号的响应。 涉及的特定基序将通过定点突变来鉴定，转录因子 结合这些位点将通过EMSA/抗体超移位方法确定。 拟议的研究将加强我们对猪瘟异常抗体反应的分子基础的理解 并为脊椎动物免疫系统中转录控制的进化提供了洞察。

The long-term goal of the proposed studies is to understand the genetic mechanisms controlling the expression of duck immunoglobulin genes. The duck has an immune response that can be characterized as ineffectual, which has significance for human health given the role of ducks (and other waterfowl) as carriers (or reservoirs) of diseases infectious for man. E.g., ducks constitute the only year-round reservoir of avian influenza A viruses, which are a source of genetic variation implicated in the emergence of novel influenza strains pathogenic to man. Understanding the molecular basis of the expression of duck antibodies will permit an understanding of their ineffectual antibody response and also contribute significantly to our understanding of the evolution of transcriptional control, an important aspect of comparative genomics. The duck has an unusual Ig heavy chain (IgH) locus, which has undergone significant rearrangement in its germline organization. The 3 constant (C) region genes are arranged mu-alpha-upsilon, with the alpha gene in reverse transcriptional orientation. This leads to unique problems of transcriptional control associated particularly with the control of class switch recombination. These are addressed in the Specific Aims of this proposal, and the hypotheses to be tested can be phrased as 3 questions: 1) Does the alpha gene have its own I-exon or does it rely on the bi-directional I-upsilon promoter to initiate class switching to IgA? 2) Have the signal transduction pathways that control Ig class-switching, by transcription from I-exon promoters, been conserved in vertebrate evolution? 3) The mammalian IgH locus contains transcriptional enhancers in both the JH to mu intron and 3' of the C-gene cluster. Where, in the duck IgH locus are the enhancers, what transcription factor-binding motifs do they contain, and how do they function? The approach involves identifying transcriptional control elements through functional analysis (i.e. their ability to drive transcription of a reporter gene), and the responsiveness of I-exon promoters to cytokine-induced class-switch signals. The specific motifs involved will be identified by site-directed mutagenesis, and the transcription factors binding these sites will be identified through EMSA/antibody supershift approaches.The results of these proposed studies will enhance our understanding of the molecular basis of the unusual antibody response of the duck, and provide insight into the evolution of transcriptional control in the vertebrate immune system.