Polycystic kidney disease (PKD), the most common genetic cause of chronic kidney failure, is characterized by the presence of numerous, progressively enlarging fluid-filled cysts in the renal parenchyma. The cysts arise from renal tubules and are lined by abnormally functioning and hyperproliferative epithelial cells. Despite recent progress, no Food and Drug Administration-approved therapy is available to retard cyst growth. MicroRNAs (miRNAs) are short noncoding RNAs that inhibit posttranscriptional gene expression. Dysregulated miRNA expression is observed in PKD, but whether miRNAs are directly involved in kidney cyst formation and growth is not known. Here, we show that miR-17∼92, an oncogenic miRNA cluster, is up-regulated in mouse models of PKD. Kidney-specific transgenic overexpression of miR-17∼92 produces kidney cysts in mice. Conversely, kidney-specific inactivation of miR-17∼92 in a mouse model of PKD retards kidney cyst growth, improves renal function, and prolongs survival. miR-17∼92 may mediate these effects by promoting proliferation and through posttranscriptional repression of PKD genes Pkd1, Pkd2, and hepatocyte nuclear factor-1β. These studies demonstrate a pathogenic role of miRNAs in mouse models of PKD and identify miR-17∼92 as a therapeutic target in PKD. Our results also provide a unique hypothesis for disease progression in PKD involving miRNAs and regulation of PKD gene dosage.cilia | kinesin family member 3A | autosomal dominant polycystic kidney disease P olycystic kidney disease (PKD) is among the most common monogenic human diseases (1, 2). PKD is characterized by the presence of numerous fluid-filled cysts in the renal parenchyma. The cysts arise from renal tubules and are lined by abnormally functioning epithelial cells. The cyst epithelial cells secrete excessive fluid and display high rates of proliferation, which results in cyst expansion. The expanding cysts compress the surrounding normal nephrons, which cause renal failure. Based on the mode of inheritance, PKD is classified into autosomal dominant PKD (ADPKD) and autosomal recessive PKD (ARPKD). ADPKD is caused by mutations of PKD1 or PKD2, which encode polycystin-1 and polycystin-2, respectively. ARPKD is caused by mutations of polycystic kidney and hepatic disease 1 (PKHD1) which encodes fibrocystin (1, 3). Polycystin-1, polycystin-2, and fibrocystin localize to the primary cilium, a sensory organelle present on the apical surface of most cells in the body. Abnormalities of the primary cilium are linked to the pathogenesis of many forms of cystic kidney diseases, including PKD (1, 4, 5). Despite recent advances, no Food and Drug Administration-approved therapy is available for PKD patients.MicroRNAs (miRNAs) are noncoding RNAs that constitute the endogenous RNA interference pathway. miRNAs are transcribed as primary miRNAs (pri-miRNAs), which are sequentially processed by the enzymes Drosha and Dicer to produce mature miRNAs (6). Watson-Crick base pairing between nucleotides 2-8 (seed sequence) at the 5′ end of the matur...
MicroRNAs (miRNAs) contribute to the regulation of early kidney development, but their role during later stages of renal tubule maturation is not well understood. Here, we found that ablation of the miRNA-processing enzyme Dicer from maturing renal tubules produces tubular and glomerular cysts in mice. Inactivation of Dicer is associated with downregulation of miR-200, a kidney-enriched miRNA family, and upregulation of the polycystic kidney disease gene Pkd1. Inhibition of miR-200 in cultured renal epithelial cells disrupted tubulogenesis and led to upregulation of Pkd1. Using bioinformatic and in vitro approaches, we found that miR-200b/c/429 induce post-transcriptional repression of Pkd1 through two conserved binding sites in the 39-Untranslated regions of Pkd1. Overexpression of PKD1 in renal epithelial cells was sufficient to disrupt tubulogenesis and produce cyst-like structures. In conclusion, miRNAs are essential for the maturation of renal tubules, and Pkd1 is a target of miR-200. These results also suggest that miRNAs may modulate PKD1 gene dosage and play a role in the initiation of cystogenesis.
Loss of function of the DIS3L2 exoribonuclease is associated with Wilms tumor and the Perlman congenital overgrowth syndrome. LIN28, a Wilms tumor oncoprotein, triggers the DIS3L2-mediated degradation of the precursor of let-7, a microRNA that inhibits Wilms tumor development. These observations have led to speculation that DIS3L2-mediated tumor suppression is attributable to let-7 regulation. Here we examine new DIS3L2-deficient cell lines and mouse models, demonstrating that DIS3L2 loss has no effect on mature let-7 levels. Rather, analysis of -null nephron progenitor cells, a potential cell of origin of Wilms tumors, reveals up-regulation of, a growth-promoting gene strongly associated with Wilms tumorigenesis. These findings nominate a new potential mechanism underlying the pathology associated with DIS3L2 deficiency.
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