Long noncoding RNA Tug1 regulates mitochondrial bioenergetics in diabetic nephropathy
Jianyin Long, … , Paul A. Overbeek, Farhad R. Danesh
Jianyin Long, … , Paul A. Overbeek, Farhad R. Danesh
Published October 17, 2016
Citation Information: J Clin Invest. 2016;126(11):4205-4218. https://doi.org/10.1172/JCI87927.
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Long noncoding RNA Tug1 regulates mitochondrial bioenergetics in diabetic nephropathy

Abstract

The regulatory roles of long noncoding RNAs (lncRNAs) in transcriptional coactivators are still largely unknown. Here, we have shown that the peroxisome proliferator–activated receptor γ (PPARγ) coactivator α (PGC-1α, encoded by Ppargc1a) is functionally regulated by the lncRNA taurine-upregulated gene 1 (Tug1). Further, we have described a role for Tug1 in the regulation of mitochondrial function in podocytes. Using a murine model of diabetic nephropathy (DN), we performed an unbiased RNA-sequencing (RNA-seq) analysis of kidney glomeruli and identified Tug1 as a differentially expressed lncRNA in the diabetic milieu. Podocyte-specific overexpression (OE) of Tug1 in diabetic mice improved the biochemical and histological features associated with DN. Unexpectedly, we found that Tug1 OE rescued the expression of PGC-1α and its transcriptional targets. Tug1 OE was also associated with improvements in mitochondrial bioenergetics in the podocytes of diabetic mice. Mechanistically, we found that the interaction between Tug1 and PGC-1α promotes the binding of PGC-1α to its own promoter. We identified a Tug1-binding element (TBE) upstream of the Ppargc1a gene and showed that Tug1 binds with the TBE to enhance Ppargc1a promoter activity. These findings indicate that a direct interaction between PGC-1α and Tug1 modulates mitochondrial bioenergetics in podocytes in the diabetic milieu.

Authors

Jianyin Long, Shawn S. Badal, Zengchun Ye, Yin Wang, Bernard A. Ayanga, Daniel L. Galvan, Nathanael H. Green, Benny H. Chang, Paul A. Overbeek, Farhad R. Danesh

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Figure 1

Tug1 OE in podocytes protects against features of DN.

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Tug1 OE in podocytes protects against features of DN. (A) Scatter plot ...
(A) Scatter plot of RNA-seq values for individual transcripts classified as noncoding RNAs. (B) Nephroseq expression data for TUG1 in control subjects (n = 13) and in subjects with DN (n =9). (C) Linear regression analysis of the same subjects in B, with eGFR values. (D) In vivo time course analysis of Tug1 expression in podocytes from diabetic and nondiabetic mice (n = 6 mice/group). (E) Schematic of Tug1Tg construct. Tug1 cDNA was cloned upstream of WPRE and hGH polyadenylation sequences. Expression is driven by the human NPHS2 (podocin) promoter. These elements are flanked by HS4 insulator sequences. Illustration shows the mating strategy to generate podocyte-specific diabetic Tug1PodTg mice. Representative image of adult control diabetic (db/db) and diabetic Tug1PodTg mice. (F) qPCR analysis of RNA isolated from podocytes measuring Tug1 levels in 24-week-old db/m (n = 5), db/db (n =5), db/m Tug1PodTg (n = 7), and db/db Tug1PodTg (n = 7) mice. (G) ACR analysis demonstrating a significant reduction in albuminuria in 24-week-old diabetic Tug1PodTg mice compared with that in controls, as in F. (H–K) Representative (H) PAS-stained image; (I) TEM micrographs; (J) SEM micrographs; and (K) nephrin immunofluorescence confocal micrographs. Red asterisks on the TEM and SEM micrographs denote effaced podocyte foot processes. Scale bars: 50 μM (H and K), 0.5 μM (I), and 1 μM (J). (L) Quantification of mesangial matrix expansion determined as the percentage of PAS-positive area/glomerular area. (M) Quantification of GBM thickness. (N) Quantification of nephrin mean fluorescence intensity (MFI)/glomerular area. (O) Quantification of WT1-positive cells/glomerular area. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001, by 2-tailed Student’s t test (B), linear regression analysis (C), and 1-way ANOVA, followed by Tukey’s post-hoc analysis (L–O). Data represent the mean ± SEM.