Identification of Mouse Airway Hyperresponsiveness Genes

气道高反应性(AHR)是哮喘的一个组成部分，哮喘和AHR的复杂遗传使人们很难找到这些重要问题的遗传病因。与人类群体相比，对异质性较小的遗传系统的分析可能有助于识别因果基因座。我们和其他人曾尝试在小鼠身上进行数量性状基因座(QTL)分析，这为NATve AHR提供了一个很好的模型，但这些研究的结果并不一致。作为该计划的一部分，我们使用了一种非常不同的方法来解决这个问题。我们创建了表型选择的重组同源基因小鼠来识别与NATve AHR增加相关的基因座。第七代高反应性小鼠在第2、6和10号染色体上保留了A/J基因座。令人惊讶的是，对未选择的N8后代的分析表明，幼稚的AHR表型与任何一个基因座都没有显著的关联，但与第2和6号染色体上的基因座的交互作用非常显著。这些发现在一项对配子体小鼠的独立分析中得到了证实。此外，作为该计划的一部分，我们培育了A/J小鼠，这些小鼠的肥大细胞基因缺失。这些小鼠没有表现出幼稚的AHR，表明这一特征是由肥大细胞介导的。AHR致病相关基因座基因组区域的鉴定 证明这一特征需要它们的相互作用，并且观察到肥大细胞是疾病表型表达所必需的，这对于剖析人类哮喘的遗传病因具有重要的意义。令人感兴趣的是，通过基因分析与人类疾病相关的蛋白酶ADAM33位于保留的A/J区。模型系统的一个优势是它们可以促进功能分析，我们建议使用单倍型分析和转基因来检查ADAM33的作用。我们还建议进一步研究肥大细胞在通过相互骨髓移植和过继移植在A/J小鼠中观察到的幼稚AHR中的作用。最后，我们将继续缩小因果基因座所在的遗传间隔，目的是最终使用位置克隆策略识别基因。

Airway hyperresponsiveness (AHR) is a component of asthma, and the complex inheritance of both asthma and AHR have made it difficult to find the genetic etiology of these important problems. Analysis in a less heterogeneous genetic system than the human population could be useful for identifying causal loci. We and others have attempted this using quantitative trait locus (QTL) analysis in the mouse, which provides an excellent model for naTve AHR, but the results of these studies have been inconsistent. As part of this Program, we have used a very different approach to address this. We created phenotypically selected recombinant congenic mice to identify loci associated with increased naTve AHR. The seventh generation hyperresponsive mice retained A/J loci on chromosomes 2, 6, and 10. Surprisingly, analysis of unselected N8 progeny demonstrated that the naive AHR phenotype was not significantly associated with any of the loci individually, but was highly significantly associated with an interaction of loci on chromosomes 2 and 6. These findings were confirmed in an independent analysis of consomic mice. Also, as part of the Program, we generated A/J mice that are genetically depleted of mast cells. These mice do not show naive AHR, demonstrating that this trait is mediated by mast cells. The identification of genomic regions containing loci causally associated with AHR, the demonstration that this trait requires their interaction, and the observation that mast cells are required for expression of the disease phenotype has important implications for the dissection of the genetic etiology of asthma in humans. Of interest is that the protease ADAM33, which has been associated with the human disease by genetic analysis, is within the retained A/J region. An advantage of model systems is that they can facilitate functional analysis, and we propose to examine the role of ADAM33 using haplotype analysis and transgenesis. We also propose to further examine the role of mast cells in mediating the naive AHR observed in A/J mice by reciprocal bone marrow transplant and adoptive transfer. Lastly, we will continue to narrow the genetic interval in which the causal loci reside, with the aim of ultimately identifying the genes using a positional cloning strategy.