Ion Transport Dysregulation in Cilium-deficient ARPKD

描述(申请人提供)：人类或小鼠模型中存在的两种遗传形式的多囊肾病(PKD)都是肾小管或上皮细胞形态和结构的深刻变化，原因是至少部分定位于皮质集合管(CCD)主细胞(PC细胞)顶端中央单纤毛的蛋白质突变。一旦PKD的遗传和生化后果在这种形态变化中表现出来，细胞或肾小管结构的变化就会深刻地影响跨上皮离子的运输。在人类常染色体隐性PKD(ARPKD)单层中，有证据表明钠的高吸收，尽管钠的转运机制尚不清楚。这一异常可能解释了大多数人类ARPKD患者出现早发性高血压的原因。利用与不朽小鼠遗传杂交而永生化的小鼠肾上皮细胞，并从野生型、突变型和遗传挽救的具有非常高电阻的橡树岭多囊肾(Oak Ridge Polycytic Ken，ORPK)小鼠的PC细胞中形成极化上皮细胞单层，我们的实验室收集了初步数据，显示小鼠Orpk ARPKD突变的皮质集合管(CCD)主要上皮细胞(PC细胞)作为极化单层生长，缺乏顶端中央单纤毛而不是对照纤毛能力强的PC细胞单层。这些上调的钠电流可能代表ENaC和NHE介导的钠高吸收。综上所述，文献、我们合作研究小组的经验、我们目前的初步工作，以及我们最初申请的评审者的建设性批评，导致我们提出了以下工作假设：缺乏心尖中枢单丝的ARPKD小鼠模型的CCDs上调了ENaC和NHE介导的钠吸收和结果高血压。相互关联的特定目标源自这一假说，旨在了解这种ARPKD疾病表型背后的细胞和分子机制。

DESCRIPTION (provided by applicant): Both genetic forms of polycystic kidney disease (PKD) present in human or mouse models as a profound change in renal tubule or epithelial cell morphology and architecture due to mutations in proteins that localize, at least in part, to the apical central monocilium of the cortical collecting duct (CCD) principal cell (PC cell). Once the genetic and biochemical consequences of PKD are manifested in this change in morphology, the change in cellular or tubular architecture affects transepithelial ion transport profoundly. In human autosomal recessive PKD (ARPKD) monolayers, there is evidence of sodium hyperabsorption, although the sodium transport mechanisms are not yet clearly defined. This abnormality may explain early onset hypertension observed in the majority of human ARPKD patients. Using mouse renal epithelial cells that are immortalized due to genetic cross with the Immortomouse and form polarized epithelial cell monolayers from wild-type, mutant, and genetically rescued PC cells from the Oak Ridge polycystic kidney (orpk) mouse CCD of very high electrical resistance, our laboratory has gathered preliminary data showing upregulated absorptive sodium transport in mouse orpk ARPKD mutant cortical collecting duct (CCD) principal epithelial cells (PC cells) grown as polarized monolayers and lacking apical central monocilia versus control cilium-competent PC cell monolayers. These upregulated sodium currents may represent ENaC- and NHE-mediated sodium hyperabsorption. Taken together, the literature, the experience of our collaborative research group, our current preliminary work, and the constructive criticism of the reviewers of our original application led us to formulate the following working hypothesis: CCDs from mouse models of ARPKD that lack apical central monocilia have upregulated ENaC- and NHE-mediated sodium absorption and resultant hypertension. Interrelated specific aims derive from this hypothesis and are designed to understand the cellular and molecular mechanisms that underlie this ARPKD disease phenotype.