Kidney Week

Abstract: SA-PO480

Loss of Mitochondrial Transcription TFAM in Renal Tubular Epithelial Cells Is Associated with Cyst Development

Session Information

• Cystic Kidney Diseases: Basic/Translational
  November 09, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidneys

• 1001 Genetic Diseases of the Kidneys: Cystic

Authors

• Kobayashi, Hanako, Vanderbilt University Medical Center, Nashville, Tennessee, United States

Hanako Kobayashi,

• Ishii, Ken, Daiichi Sankyo Co. Ltd., Tokyo, Japan

Ken Ishii,

• Taguchi, Kensei, Department of Nephrology and Hypertension, Nashville, Tennessee, United States

Kensei Taguchi,

• Brooks, Craig R., Vanderbilt University Medical Center/Division of Nephrology & Hpertension, Nashville, Tennessee, United States

Craig R. Brooks,

• Haase, Volker H., Vanderbilt University Medical Center, Nashville, Tennessee, United States

Volker H. Haase,

Background

Mitochondrial dysfunction plays an important role in the pathogenesis of kidney disease. In fact, certain kidney diseases are associated with genetic mitochondrial disorders, indicating that mitochondrial dysfunction can initiate and promote kidney disease.

Methods

In the kidney, mitochondria (mt) are highly abundant in renal tubular epithelial cells due to their high energy demands. In order to gain insights into mt function during renal pathogenesis, we inactivated the gene encoding mt transcription factor A (TFAM) in Six2-expressing progenitor cells, resulting in TFAM function loss in all nephron segments except collecting ducts; mutant mice are from hereon refered to as Six2-Tfam^-/- mutants. TFAM is required for mt DNA replication and gene transcription and is thus essential for the maintenance of mt mass and function.

Results

We found that Six2-Tfam^-/- mice developed severe renal cystic disease and died by postnatal day (P) 30 from renal failure (76.0 ± 3.46 mg/dL for mutants vs. 22.0 ± 2.0 mg/dL BUN for control; n=4 and n=3, respectively; p<0.0001). Although nephrogenesis was not affected (normal morphology at P0), the expression of proximal and distal renal differentiation markers was severely reduced by P7. Furthermore, Six2-Tfam^-/- mice were characterized by significant changes in mt morphology {EM and structured illumination microscopy (SIM)}, as well as alterations in cellular energy metabolism; increase in glycolysis and decrease in oxygen consumption in isolated proximal tubule epithelial cells using Seahorse XF-24 instrument. To investigate TFAM in autosomal dominant polycystic kidney disease (ADPKD), we examined two mouse models of ADPKD, ROSA26-Cre^ERTPkd1^-/- and Cys^cpk/cpk mice as well as human nephrectomy tissues by immunohistochemistry and RNA in situ hybridization. We observed that TFAM as well as TFAM-regulated mt genes were signifcantly downregulated in cyst-lining epithelial cells in both mouse and human PKD tissues. Consistent with reduced TFAM expression was a decrease in mt volume in cyst-lining epithelial cells compared to non-cystic tubular epithelium using SIM.

Conclusion

Taken together, our data establish that loss of TFAM is associated with the development of polycystic renal disease providing strong rational for developing strategies that target mt function for ADPKD therapy.

Funding

• NIDDK Support