Immunobiology of IFRD1, a gene modifying CF lung disease

描述（由申请人提供）：囊性纤维化（CF）是美国最常见的致死性常染色体隐性遗传病，CF肺病是发病率和死亡率的主要原因，显然需要新的治疗方法。已发表的研究表明，CF患者肺部疾病严重程度的显著遗传性与CFTR基因型无关。为了寻找改变CF肺病的基因，我们在一个CF患者队列中进行了全基因组关联扫描，并在一个独立队列中复制了顶级候选基因。使用这种方法，IFRD1的遗传变异被确定并复制为CF肺部疾病严重程度的修饰因子。IFRD1是一种转录共调节因子，以组蛋白去乙酰化酶（HDAC）依赖的方式起作用。虽然IFRD1在许多细胞类型中表达，但它似乎在中性粒细胞（pmn）中表达得最高。我们的数据表明，PMN分化与IFRD1表达上调有关；Ifrd1-/-小鼠的pmn（而非巨噬细胞）效应功能受损。CF气道的炎症反应持续呈中性粒细胞性；反过来，活化PMNs的产物似乎是CF中气道破坏的原因。我们的数据表明，在呼吸道感染铜绿假单胞菌后，Ifrd1-/-小鼠表现出明显较慢的细菌清除；还能显著减少中性粒细胞炎症和疾病。这种表型严格依赖于造血细胞IFRD1的表达。此外，HDAC抑制导致野生型小鼠的气道炎症反应特异性减弱，而不是Ifrd1-/-小鼠，这表明Ifrd1以HDAC依赖的方式调节气道炎症。骨髓移植技术和细胞内细胞因子产生分析将这些作用定位于PMNs。最后，对正常供体PMN的分析揭示了IFRD1多态性与PMN效应功能的定量测量之间的显著关联。综上所述，这些数据提出了支持这一建议的相互关联的假设：(a) IFRD1是CF肺病的修饰基因；(b) IFRD1通过调节PMN效应物功能调节CF中气道疾病的发病机制；(c) IFRD1多态性改变PMN功能。本提案中的研究将确定IFRD1介导的PMN功能调节的生物学后果和细胞和分子机制，并确定IFRD1中改变CF肺部疾病表达的因果变异。公共卫生相关性：囊性纤维化是欧洲背景人群中最常见的致命性常染色体隐性遗传病，在美国的发病率约为30,000。肺部疾病是囊性纤维化发病和死亡的主要原因。尽管近几十年来囊性纤维化的治疗取得了相当大的进展，但该疾病患者的中位生存期仍约为35年。因此，迫切需要新的治疗方法囊性纤维化肺疾病。我们已经确定（并验证）了一个改变囊性纤维化肺病严重程度的基因：IFRD1。本提案中的研究将确定IFRD1改变囊性纤维化肺部疾病严重程度的分子机制，并以开发这种毁灭性疾病的新治疗方法为长期目标。

DESCRIPTION (provided by applicant): Cystic fibrosis (CF) is the most common, lethal autosomal recessive disorder in the U.S. Novel therapeutic approaches to CF lung disease, the major cause of morbidity and mortality, are clearly needed. Published studies indicate significant heritability of lung disease severity in CF, independent of CFTR genotype. To search for genes modifying CF lung disease, we performed a genome-wide association scan in one cohort of CF patients, with replication of top candidates in an independent cohort. Using this approach, genetic variation in IFRD1 was identified and replicated as a modifier of lung disease severity in CF. IFRD1 is a transcriptional co-regulator that acts in a histone deacetylase (HDAC)-dependent manner. While expressed in numerous cell types, IFRD1 appears to be expressed most highly in neutrophils (PMNs). Our data indicate that PMN differentiation is associated with upregulation of IFRD1 expression; and that PMNs (but not macrophages) from Ifrd1-/- mice have impaired effector function. The inflammatory response in the CF airway is persistently neutrophilic; in turn, the products of activated PMNs appear to be responsible for airway destruction in CF. Our data demonstrate that, after airway infection with P. aeruginosa, Ifrd1-/- mice exhibit significantly slower bacterial clearance; but also significantly less neutrophilic inflammation and disease. This phenotype is strictly dependent upon hematopoietic cell expression of IFRD1. Further, HDAC inhibition leads to specific blunting of airway inflammatory responses in wild type, not Ifrd1-/- mice, indicating that IFRD1 acts in an HDAC-dependent fashion to regulate airway inflammation. Bone marrow transfer techniques and intracellular analysis of cytokine production localized these effects to PMNs. Finally, analysis of PMNs from normal human donors has revealed significant association of IFRD1 polymorphisms with quantitative measures of PMN effector function. Together, these data suggest the inter-related hypotheses that underlie this proposal: (a) IFRD1 is a modifier gene for CF lung disease; (b) IFRD1 modulates the pathogenesis of airway disease in CF through regulation of PMN effector function; and (c) polymorphisms in IFRD1 alter PMN function. The studies in this proposal will define the biological consequences and cellular and molecular mechanisms underlying IFRD1- mediated modulation of PMN function, as well as identify the causal variants in IFRD1 that modify the expression of CF lung disease. PUBLIC HEALTH RELEVANCE: Cystic fibrosis is the most common, lethal autosomal recessive disorder in those with European backgrounds-with an incidence in the United States of approximately 30,000. Lung disease is the major cause of morbidity and mortality in cystic fibrosis. Despite considerable progress in the therapy of cystic fibrosis in recent decades, the median survival of patients with this disease remains around 35 years. There is thus a pressing need for new therapeutic approaches to cystic fibrosis lung disease. We have identified (and validated) a gene that modifies the severity of cystic fibrosis lung disease: IFRD1. The studies in this proposal will define the molecular mechanisms by which IFRD1 modifies lung disease severity in cystic fibrosis, with the long-term goal of developing novel therapeutic approaches to this devastating disease.