Autosomal dominant polycystic kidney disease (ADPKD) is a debilitating disease that is characterized by the accumulation of numerous fluid-filled cysts in the kidney. ADPKD is primarily caused by mutations in two genes, PKD1 and PKD2. Long noncoding RNAs (lncRNA), defined by a length >200 nucleotides and absence of a long ORF, have recently emerged as epigenetic regulators of development and disease; however, their involvement in PKD has not been explored previously. Here, we performed deep RNA-Seq to identify lncRNAs that are dysregulated in two orthologous mouse models of ADPKD (kidney-specific Pkd1 and Pkd2 mutant mice). We identified a kidney-specific, evolutionarily conserved lncRNA called Hoxb3os that was down-regulated in cystic kidneys from Pkd1 and Pkd2 mutant mice. The human ortholog HOXB3-AS1 was down-regulated in cystic kidneys from ADPKD patients. Hoxb3os was highly expressed in renal tubules in adult WT mice, whereas its expression was lost in the cyst epithelium of mutant mice. To investigate the function of Hoxb3os, we utilized CRISPR/Cas9 to knock out its expression in mIMCD3 cells. Deletion of Hoxb3os resulted in increased phosphorylation of mTOR and its downstream targets, including p70 S6 kinase, ribosomal protein S6, and the translation repressor 4E-BP1. Consistent with activation of mTORC1 signaling, Hoxb3os mutant cells displayed increased mitochondrial respiration. The Hoxb3os mutant phenotype was partially rescued upon re-expression of Hoxb3os in knockout cells. These findings identify Hoxb3os as a novel lncRNA that is down-regulated in ADPKD and regulates mTOR signaling and mitochondrial respiration.
Bibliographical noteFunding Information:
This work was supported by the National Institutes of Health Grants R37DK042921 (to P. I.) and UL1TR001105 (to C. X.). The authors declare that they have no conflicts of interest with the contents of this article. The con-tent is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. The RNA sequences for this project can be accessed through the NCBI under Gene Expression Omnibus accession number GSE108864. This article contains Figs. S1–S6. 1To whom correspondence should be addressed: 420 Delaware St. SE, MMC 605, Minneapolis, MN. Tel.: 612-625-0530; E-mail: email@example.com. 2 The abbreviations used are: ADPKD, autosomal dominant polycystic kidney disease; lncRNAs, long noncoding RNAs; PhyloCSF, phylogenetic codon
© 2018 Michalski and Williams Published under exclusive license by The American Society for Biochemistry and Molecular Biology, Inc.