To Explore and Study Domain Functions of Fibrocystin using Animal Models

描述(由申请人提供)：最近的报告表明，纤维囊蛋白/多导管蛋白(FPC)，其突变导致常染色体隐性遗传性多囊肾病(ARPKD)，可以被切割，其细胞外结构域(FPCEXD)通过肾上皮细胞的顶端表面释放到肾小管腔内(Hogan等人，2009；Kaimori等人，2007)。因此，我们推测FPCEXD也可能在肾小管形态发生和/或器官发生中发挥重要作用。FPCEXD缺失可能导致ARPKD的囊变。我们目前已经建立了表达突变Pkhd1的小鼠模型(Kim等人，2008年)及其转基因动物(黄S，2007年)，并从这些模型中建立了肾脏收集细胞系(Hu等人，2011年)。除了上述模型系统外，我们还建立了一个新的Pkhd1f65突变小鼠系，在该系中，FPC的整个跨膜区(FPC-STD)可以通过Cre重组酶的诱导在空间和时间上被分离出来。利用这些模型系统，我们能够确定FPCEXD在小鼠胚胎发生或器官发生中是否发挥重要功能，FPCEXD在发育中的小鼠是否会诱导致死性表型和囊性表型；异位FPCEXD的过度表达是否能挽救Pkhd1基因缺陷小鼠的ARPKD表型；以及暂时恢复FPCEXD功能是否能阻止或逆转患病肾脏的囊性表型，从而保护或恢复正常肾组织。通过研究这些小鼠及其衍生的细胞系，我们将进一步深入了解分泌型FPC在胚胎发生、器官发生和囊变发生中的调控作用。这些发现将有助于阐明ARPKD的发病机制，并可能为人类ARPKD的治疗干预奠定基础。

DESCRIPTION (provided by applicant): Recent reports have demonstrated that fibrocystin/polyductin (FPC), whose mutations cause autosomal recessive polycystic kidney disease (ARPKD), can be cleaved and its extracellular domain (FPCEXD) is released through the apical surface of renal epithelial cells into the lumen of renal tubules (Hogan et al., 2009; Kaimori et al., 2007). We therefore hypothesize that FPCEXD may also play essential functions in tubulomorphogenesis and/or organogenesis. Lack of FPCEXD may result in cystogenesis of ARPKD. We have currently produced the mouse models expressing mutant Pkhd1 (Kim et al., 2008) and its transgene (Huang S, 2007), and developed renal collecting cell lines from these models as well (Hu et al., 2011). Besides the above model systems, we have also generated a new Pkhd1f65 mutant mouse line in which the entire single transmembrane domain of FPC (FPC-STD) can be spatially and temporally floxed out by induction of Cre recombinase. Using these model systems, we are able to determine whether the FPCEXD plays important functions in mouse embryogenesis or organogenesis, and whether FPCEXD overexpression in the developing mouse induces lethal phenotypes and cystic phenotypes; whether ectopic FPCEXD overexpression can rescue ARPKD phenotypes in our Pkhd1-deficient mice; and whether temporal restoration of FPCEXD function can halt or reverse cystic phenotypes in diseased kidneys, thus preserving or restoring normal renal tissue. By studying these mice as well as the cell lines derived from them, we will gain further insights into the role of secretory FPC in the regulation of embryogenesis, organogenesis, and cystogenesis. These findings will shed light on the pathogenesis of ARPKD and may develop fundamental basis for therapeutic intervention of human ARPKD.