FGF9 REGULATION OF LUNG DEVELOPMENT AND PATHOGENESIS OF PLEUROPULMONARY BLASTOMA

描述（由申请人提供）：肺部疾病的起源通常在发育过程中开始。揭示调控发育的复杂机制对于理解发育性、遗传性和获得性肺部疾病的发病机制至关重要。本研究主要围绕成纤维细胞生长因子9 （FGF9）信号调控肺发育的机制展开。FGF9产生于肺上皮和间皮，主要调控间质，在肺上皮的调节中起直接和间接的次要作用。我们已经确定了一个前馈调节网络，涉及间质FGF受体（FGFR）和Wnt/¿-catenin信号传导。在首次提交该提案后发表的数据中，我们发现FGF和Wnt/¿-catenin通路在体内都能抑制Noggin。这一发现将间充质FGF-Wnt/¿-catenin信号通路与调节上皮生长和分化的Bmp通路结合起来。另一种深入了解发育机制的方法是研究癌症的发病机制，这是一种经常采用胚胎调控机制的疾病。肺间质FGF9信号传导与遗传性儿童肺癌综合征胸膜肺母细胞瘤（PPB）之间的潜在联系。PPB很有趣，因为它起源于胚胎期的肺间充质细胞。诱导过表达FGF9的小鼠胚胎肺发生与I型PPB相似的组织学间充质增生，提示FGF9可能参与PPB的发病机制。PPB的遗传起源被定位为microRNA （miRNA）加工基因DICER1的功能缺失突变。初步和已发表的数据显示，发育中的肺上皮Dicer1消融模拟了PPB的早期囊性阶段。DICER1突变的PPB肿瘤的免疫组化研究经常显示肺上皮DICER1表达降低。这些观察结果提示了一种解释PPB发病机制的模型，其中DICER1处理的上皮mirna减少导致上皮基因过表达和一种因子的产生，该因子刺激邻近间质增殖，使间质易发生肿瘤转化。初步数据提供了证据，表明上皮来源的FGF9介导了DICER1中功能丧失突变的一些致病后果。我们推测Fgf9可能是dicer1介导的miRNA通路直接调控的主要致病基因。在本研究中，我们将：1)阐明间质FGF和Wnt/¿-catenin信号调控Noggin表达和BMP通路活性的机制；2)在小鼠PPB模型中验证FGF9是间充质增生的致病介质的假设；3)比较FGF9和Wnt/¿-catenin信号通路调控的肺间质转录格局，以及FGF9和Dicer1小鼠模型与早期人类PPB的差异。

DESCRIPTION (provided by applicant: The origins of lung disease often begin during development. Unraveling the complex mechanisms that regulate development is essential for understanding the pathogenesis of developmental, genetic and acquired lung disease. This proposal is focused around the mechanisms by which Fibroblast Growth Factor 9 (FGF9) signaling regulates lung development. FGF9 is made in lung epithelium and mesothelium and has a major role in regulating mesenchyme and secondary direct and indirect roles in the regulation of lung epithelium. We have identified a feed-forward regulatory network that involves mesenchymal FGF receptor (FGFR) and Wnt/¿-catenin signaling. In data published since the first submission of this proposal, we showed that both FGF and Wnt/¿-catenin pathways function in vivo to suppress Noggin. This finding couples mesenchymal FGF-Wnt/¿-catenin signaling with Bmp pathways that regulate epithelial growth and differentiation. Another means to gain insight into developmental mechanisms is to study the pathogenesis of cancer, a disease which often co-opts embryonic regulatory mechanisms. A potential link between FGF9 signaling in lung mesenchyme and human lung disease involves the heritable pediatric lung cancer syndrome, pleuropulmonary blastoma (PPB). PPB is interesting because it arises from embryonic uncommitted lung mesenchymal cells. Mouse embryonic lung that was induced to overexpress FGF9 develops mesenchymal hyperplasia with histology that mimics that of type I PPB, suggesting that FGF9 might be involved in the pathogenesis of PPB. The genetic origins of PPB were mapped to loss-of-function mutations in the microRNA (miRNA) processing gene, DICER1. Preliminary and published data shows that Dicer1 ablation in developing lung epithelium mimics the early cystic stage of PPB. Immunohistochemical studies of PPB tumors with mutations in DICER1 often show decreased DICER1 expression in lung epithelium. These observations suggest a model to explain the pathogenesis of PPB in which decreased epithelial miRNAs processed by DICER1 results in overexpression of an epithelial gene(s) and production of a factor(s) that stimulates the proliferation of adjacent mesenchyme, predisposing the mesenchyme to neoplastic transformation. Preliminary data provides evidence that implicates epithelial-derived FGF9 in mediating some of the pathogenic consequences of loss-of-function mutations in DICER1. We hypothesize that Fgf9 may be a major pathogenic gene that is directly regulated by DICER1-mediated miRNA pathways. In this proposal, we will: 1) Elucidate the mechanism by which mesenchymal FGF and Wnt/ ¿-catenin signaling regulates Noggin expression and activity of the BMP pathway; 2) Test the hypothesis that FGF9 is a pathogenic mediator of mesenchymal hyperplasia in a mouse model for PPB; and 3) Compare the lung mesenchymal transcriptional landscape regulated by FGF9 and Wnt/¿-catenin signaling and by Fgf9 and Dicer1 mouse models for PPB with early stage human PPB.