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, and 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 and mutant mice). We identified a kidney-specific, evolutionarily conserved lncRNA called that was down-regulated in cystic kidneys from and mutant mice. The human ortholog was down-regulated in cystic kidneys from ADPKD patients. 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, we utilized CRISPR/Cas9 to knock out its expression in mIMCD3 cells. Deletion of 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, mutant cells displayed increased mitochondrial respiration. The mutant phenotype was partially rescued upon re-expression of in knockout cells. These findings identify as a novel lncRNA that is down-regulated in ADPKD and regulates mTOR signaling and mitochondrial respiration.

The transcription factor hepatocyte nuclear factor-1 (HNF-1) is essential for normal kidney development and function. Inactivation of HNF-1 in mouse kidney tubules leads to early-onset cyst formation and postnatal lethality. Here, we used Pkhd1/Cre mice to delete HNF-1 specifically in renal collecting ducts (CDs). CD-specific HNF-1 mutant mice survived long term and developed slowly progressive cystic kidney disease, renal fibrosis, and hydronephrosis. Compared with wild-type littermates, HNF-1 mutant mice exhibited polyuria and polydipsia. Before the development of significant renal structural abnormalities, mutant mice exhibited low urine osmolality at baseline and after water restriction and administration of desmopressin. However, mutant and wild-type mice had similar plasma vasopressin and solute excretion levels. HNF-1 mutant kidneys showed increased expression of aquaporin-2 mRNA but mislocalized expression of aquaporin-2 protein in the cytoplasm of CD cells. Mutant kidneys also had decreased expression of the UT-A urea transporter and collectrin, which is involved in apical membrane vesicle trafficking. Treatment of HNF-1 mutant mIMCD3 cells with hypertonic NaCl inhibited the induction of osmoregulated genes, including , which encodes the transcription factor FXR that is required for maximal urinary concentration. Chromatin immunoprecipitation and sequencing experiments revealed HNF-1 binding to the promoter in wild-type kidneys, and immunoblot analysis revealed downregulated expression of FXR in HNF-1 mutant kidneys. These findings reveal a novel role of HNF-1 in osmoregulation and identify multiple mechanisms, whereby mutations of HNF-1 produce defects in urinary concentration.

Mutations in hepatocyte nuclear factor 1β (HNF1β) cause autosomal dominant tubulointerstitial kidney disease (ADTKD-HNF1β), and patients tend to develop renal cysts, maturity-onset diabetes of the young (MODY), and suffer from electrolyte disturbances, including hypomagnesemia, hypokalemia, and hypocalciuria. Previous HNF1β research focused on the renal distal convoluted tubule (DCT) to elucidate the ADTKD-HNF1β electrolyte phenotype, although 70% of Mg is reabsorbed in the thick ascending limb of Henle's loop (TAL). An important regulator of Mg reabsorption in the TAL is the calcium-sensing receptor (CaSR). This study used several methods to elucidate the role of HNF1β in electrolyte reabsorption in the TAL. HNF1β ChIP-seq data revealed a conserved HNF1β binding site in the second intron of the CaSR gene. Luciferase-promoter assays displayed a 5.8-fold increase in CaSR expression when HNF1β was present. Expression of the HNF1β p.Lys156Glu mutant, which prevents DNA binding, abolished CaSR expression. Hnf1β knockdown in an immortalized mouse kidney TAL cell line (MKTAL) reduced expression of the CaSR and Cldn14 (claudin 14) by 56% and 48%, respectively, while Cldn10b expression was upregulated 5.0-fold. These results were confirmed in a kidney-specific HNF1β knockout mouse, which exhibited downregulation of the Casr by 81%. Cldn19 and Cldn10b expression levels were also decreased by 37% and 83%, respectively, whereas Cldn3 was upregulated by 4.6-fold. In conclusion, HNF1β is a transcriptional activator of the CaSR. Consequently, patients with HNF1β mutations may have reduced CaSR activity in the kidney, which could explain cyst progression and hyperabsorption of Ca and Mg in the TAL resulting in hypocalciuria.

Background Imported cases of arbovirus infections associated with persistent arthralgia in travelers returning from endemic areas are often misdiagnosed due to overlapping clinical presentations and lack of widely available diagnostic testing. Identifying differences in joint involvement between arboviruses that cause persistent arthralgia may facilitate an earlier diagnosis. The purpose of this study was to determine if such distinct joint involvement has been reported in published literature for arbovirus-associated persistent arthralgia. Methods Chikungunya (CHIKV), Ross River Virus (RRV), Sindbis Virus (SINV) and Mayaro Virus (MAYV) were selected for their association with persistent arthralgia. Candidate manuscripts were identified using the PubMed database and search terms included virus names as well as terms associated with persistent arthralgia. Inclusion criteria consisted of 1) patient data on persistent arthralgia and 2) description of joint involvement. Joint involvement data was manually extracted and compared between viruses using a Fisher’s exact test. Pairwise post-hoc comparisons were then conducted using Fisher’s exact test and a Bonferroni correction was applied. Results Data from 1,833 patients were extracted from 57 manuscripts that met inclusion criteria (RRV = 194, SINV = 87, CHIKV = 1,526, MAYV = 26). Reported involvement of hands, wrists, elbows, shoulders, ankles and knees were recorded (Table 1). Distribution of joint involvement was then calculated for each virus (Figure 1). The difference in distribution of joint pain between the four arboviruses was statistically significant (P = 0.004). Comparisons revealed RRV and CHIKV are distinguishable from each other (P = 0.004). Table 1. Reported Joint Involvement Figure 1. Distribution of Joint Involvement Conclusion These findings suggest that differences in distribution in joint involvement may exist between patients with persistent arthralgia following arbovirus infection. Future studies aimed at more clearly elucidating these differences are warranted and may help develop a more rapid and accurate diagnostic algorithm that could improve patient care. Disclosures All Authors: No reported disclosures

No abstract