Modifier Genes of SP-C Induced ILD

间质性肺病(ILDS)是一种具有多种潜在病因的慢性进行性肺部疾病，但大多数病因尚不清楚。患有这些疾病的患者通常在临床上无法区分，表现为与运动受限、呼吸急促和呼吸急促相关的进展性ILD。在病理上，各种类型的ILD均与肺泡炎、肺间质浸润结缔组织基质和白细胞、进行性肺泡结构丧失和肺纤维化有关。尽管公认的组织学和临床表现，参与ILD发病的分子机制一直是难以捉摸的。许多已知的家族性遗传病都含有ILD成分，包括肺泡蛋白沉积症、高谢病、Hermansky-Pudlak综合征、Neimann-Pick病、神经纤维瘤病和结节性硬化症。然而，除了已知疾病之外，对ILDS的易感性被认为只有很小的家族因素。最近，人类ILD与常染色体显性突变有关 表面活性蛋白-C(SP-C)基因。这导致上皮中II型细胞特异性SP-C蛋白的功能丧失，导致肺泡细胞损伤，并易患各种形式的ILD。这些发现扩展了早期的研究，即与诊断为家族性ILD的家庭成员的SP-C基因突变和蛋白质缺乏有关。家族性ILD的一个有趣但麻烦的特征是在受影响的个体中看到的组织病理模式的高度变异性，强烈暗示修饰基因与ILD的严重程度有关。ILD修饰基因的额外证据来自于基因敲除的小鼠。当在FVB/N小鼠中以SP-C为基因靶点时，只有细微的变化 记录肺力学和组织学变化。相反，129S6/SvEvTac(129/Sv)SP-C缺失小鼠出现了严重的进行性肺部疾病，许多组织学特征与ILD一致；因此，129/Sv品系中SP-C缺乏代表了ILD的小鼠模型。这项研究的中心假设是，SP-C缺失状态下的ILD严重程度由一个或多个基因改变，这些基因可以通过对FVB/N-129/Sv小鼠模型的遗传和分子分析来描述。识别影响ILD严重程度的修饰基因将使用4个具体目标来完成：1)确定每个中间ILD表型的可能的遗传模式，并估计影响不同类型ILD的最小基因座数量 该方法包括：1)确定SP-C缺失小鼠模型中的肺脏反应(分离分析)；2)在由两个SP-C缺失品系产生的大型回交队列中识别与表型差异相关的染色体区域(QTL分析)；3)识别与SP-C缺失小鼠品系差异相关的候选和位置候选修饰基因(基因芯片分析)；4)评估SP-C缺失小鼠模型中的位置候选ILD修饰基因(功能分析)。基因鉴定应该产生进一步评估治疗策略和影响表面活性物质相关肺部疾病的易感性和预后的基因变异所需的有价值的信息。

Interstitial lung diseases (ILDs) are chronic, progressive lung diseases with many potential causes; however, most etiologies are unknown. Patients with these disorders are often clinically indistinguishable, presenting with advancing ILD that is associated with exercise limitation, tachypnea, and shortness of breath. Pathologically, the various forms of ILD are all associated with alveolar inflammation, pulmonary interstitial infiltration with connective tissue matrix and leukocytes, progressive loss of alveolar structure, and pulmonary fibrosis. Despite well-recognized histological and clinical manifestations, the molecular mechanisms involved in ILD pathogenesis have been elusive. Many known familial genetic disorders have an ILD component, including pulmonary alveolar proteinosis, Gaucher disease, Hermansky-Pudlak syndrome, Neimann-Pick disease, neurofibromatosis, and tuberous sclerosis. Susceptibility to ILDs beyond those for known disorders, however, is believed to have only a minor familial component. Recently, human ILD was associated with an autosomal dominant mutation in the surfactant protein-C (SP-C) gene. This resulted in a functional loss of Type II cell specific SP-C protein in the epithelium, causing alveolar cell injury and predisposing to various forms of ILD. These findings extended earlier studies that associated SP-C gene mutations and protein deficiency in family members diagnosed with familial ILD. An intriguing, but troublesome attribute of familial ILD is the high variability in histopathologic patterns seen among affected individuals, strongly implicating modifier genes in ILD severity. Additional evidence for modifier genes of ILD stems from knockout mice. When SP-C was gene-targeted in FVB/N mice, only subtle changes in lung mechanics and histology were noted. To the contrary, 129S6/SvEvTac (129/Sv) SP-C null mice developed severe and progressive pulmonary disease with many histological features consistent with ILD; thus, SP-C deficiency in the 129/Sv strain represents a mouse model of ILD. The central hypothesis of the proposed research is that ILD severity in a SP-C null state is modified by one or more genes, which can be delineated using genetic and molecular analyses of the FVB/N-129/Sv mouse model. Identification of modifier genes affecting ILD severity will be accomplished using 4 Specific Aims: 1) determine the likely mode of inheritance for each intermediate ILD phenotype and estimate the minimum number of loci affecting the disparate lung responses in the SP-C null mouse model (segregation analysis); 2) identify chromosomal regions linked to phenotype differences in a large backcross cohort generated from the two SP-C null strains (QTL analysis); 3) identify candidate and positional candidate modifier genes associated with strain differences in SP-C null mice (microarray analysis); and 4) assess positional candidate ILD modifier genes in the SP-C null mouse model (functional analysis). Gene identification should yield valuable information needed to further assess therapeutic strategies and genetic variations affecting susceptibility and outcome of surfactant-associated lung diseases.