A model of kidney stone disease using D. melanogaster

症状性肾结石可能是严重疼痛、感染和发病的重要来源，影响多达12%的美国人，每年产生超过20亿美元的医疗费用。肾结石形成的过程仍然知之甚少，并且由于缺乏良好的肾结石形成模型，在开发药物或饮食干预以预防结石发生或复发方面进展有限。 果蝇（Drosophilamelanogaster，D.在哺乳动物（黑腹果蝇）中，马氏管是人曲小管的功能等同物，并将离子和其他溶质从果蝇循环系统转运到排泄系统中。此外，在苍蝇排泄系统中发现的许多基因在人类排泄系统中起保守作用。苍蝇小管产生含有钙、磷和其他离子与有机基质结合的结晶结核。这些结石似乎是由小的球形结构形成的，这些结构与兰德尔斑块中看到的纳米颗粒（球状体）有着惊人的相似之处，兰德尔斑块是人类肾脏早期结石形成的病灶。我们发现，这些飞石含有黄嘌呤和二磷酸盐结合物质，可能是羟基磷灰石和钙，早期人类结石的主要成分。我们还发现，抑制黄嘌呤脱氢酶（XDH）在D。在高蛋白饮食中，黑腹菌导致结石积累增加，这可以通过抑制维生素D受体直系同源物来挽救。值得注意的是，这些基因和高蛋白饮食与人类结石病有关。由于D.黑腹果蝇和人类，以及强大的遗传工具在苍蝇中的可用性，我们假设D。黑腹菌可以作为一个有意义的模型，以提高对肾结石疾病的理解，并确定新的治疗方法。 本研究的目的是：（1）XDH敲除果蝇早期结石形成和小管生理学的特征;（2）鉴定调节早期果蝇结石形成的遗传和药理学操作。黑腹菌作为研究肾结石的转化模型的重要性在于，它将为更好地理解人类肾结石形成的机制和发现肾结石疾病的新疗法提供机会。该提议是创新的，因为应用了以短寿命和相对低的维持成本为特征的无脊椎动物翻译模型，以实现用于开发肾结石治疗剂的遗传和药理学操作的大规模筛选。

DESCRIPTION (provided by applicant): Symptomatic kidney stones can be a significant source of severe pain, infection, and morbidity, affecting up to 12% of Americans and generating more than $2 billion in healthcare costs annually. The process of kidney stone formation remains poorly understood and there has been limited progress in developing medical or dietary interventions to prevent the occurrence or recurrence of stones due to paucity of good models for kidney stone formation. In Drosophila melanogaster (D. melanogaster), the Malpighian tubule is the functional equivalent of the human convoluted tubule and transports ions and other solutes from the fly circulatory system into the excretory system. Furthermore, a number of genes found in the fly excretory system play a conserved role in the human excretory system. The fly tubule produces crystalline concretions containing calcium, phosphorus, and other ions combined with an organic matrix. These concretions appear to be formed from small spherical structures that bear a striking resemblance to the nanoparticles (spherites) seen in Randall plaques, the nidus of early stone formation in human kidneys. We show that these fly stones contain xanthine and a bisphosphonate-binding substance, presumably hydroxyapatite and calcium, the primary component of early human stones. We have also found that inhibition of xanthine dehydrogenase (XDH) in D. melanogaster leads to increased accumulation of concretions on a high protein diet which can be rescued by inhibition of a Vitamin D receptor ortholog. Notably these genes and a high protein diet have been implicated in human stone disease. Given the similarities in tubule physiology, conservation of genes in the excretory system, and characteristics of stone formation between D. melanogaster and humans, and the availability of powerful genetic tools in the fly, we hypothesize that D. melanogaster can be utilized as a meaningful model to improve understanding of kidney stone disease and to identify novel therapeutics. The aims of the proposed study are: (1) Characterization of early stone formation and tubule physiology in the XDH knockdown fly; and (2) identification of genetic and pharmacologic manipulations that modulate early fly stone formation, The significance of developing D. melanogaster as a translational model for studying nephrolithiasis is that it would provide an opportunity to better understand the mechanism of human kidney stone formation and to discover novel therapeutics for kidney stone disease. This proposal is innovative because of the application of an invertebrate translational model characterized by a short lifespan and relatively low cost of maintenance, to achieve large scale screening of genetic and pharmacological manipulations for developing therapeutics for nephrolithiasis.