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Kidney Week

Abstract: SA-PO776

Identification of Transcripts Critical to Tuberous Sclerosis Complex (TSC)-mTOR Axis Dysregulation in Tuberous Sclerosis Complex Renal Cystic Disease

Session Information

Category: Genetic Diseases of the Kidneys

  • 1201 Genetic Diseases of the Kidneys: Cystic

Authors

  • Zahedi, Kamyar A., New Mexico VA Health Care System, Albuquerque, New Mexico, United States
  • Barone, Sharon L., New Mexico VA Health Care System, Albuquerque, New Mexico, United States
  • Zaidman, Nathan, University of New Mexico Health Sciences Center, Albuquerque, New Mexico, United States
  • Soleimani, Manoocher, New Mexico VA Health Care System, Albuquerque, New Mexico, United States
Background

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder caused by mutations in TSC1 or TSC2 genes, and affects over two million individuals worldwide. In the kidney, TSC is associated with the development of cysts and angiomyolipomata, leading to renal failure. The cyst epithelia in various models of Tsc knockout mice (e.g., principal cell specific KO of Tsc1 or Tsc2, pericyte specific KO of Tsc1, and heterozygote Tsc2+/-), as well humans with TSC is overwhelmingly comprised of hyper-proliferating A-intercalated cells (ICs). Deletion of Foxi1, the transcription factor critical to the acid secretion and IC viability, completely abrogated the cystogenesis in Tsc1 KO mice.

Methods

RNA-seq analyses comparing the renal transcriptome of Wildtype (WT), Tsc1 KO, Tsc1/Foxi1 dKO, and Foxi1 KO mice were used to identify the differentially expressed transcripts (DET) that were activated in Tsc1 KO (exhibiting many cysts) and downregulated in Tsc1/Foxi1 dKO (that had no cysts) mice. The expression levels of mRNAs and proteins of interest were confirmed by northern and western blot analysis, and their localization was ascertained by immunofluorescence microscopy.

Results

RNA-seq analyses identified arginine vasopressin receptor 1a (Avpr1a) and the oncogene c-Kit (a receptor tyrosine kinase) as DET with robust activation in the kidneys of Tsc1 KO mice and complete abrogation in Tsc1/Foxi1 dKO mice. Northern and Western blot analyses confirmed the increased expression of Avpr1a and c-Kit, and immunofluorescence displayed abundant labeling of both proteins on the basolateral membrane of ICs lining the cysts in Tsc1 KO mice. KEGG enrichment analysis and expression studies showed the activation of MAPK and PI3K/AKT pathways, which are critical in AVPR1 and c-KIT signal transduction. Further, Tsc2 in ICs lining the cysts was shown to be phospho-inactivated on multiple ERK, AKT and RSK1 target sites.

Conclusion

The activation of AVPR1a and c-KIT oncogene, in association with enhanced ERK1/2 signaling and TSC2 inactivation, point to a novel pathway that disrupts the TSC/mTORC1 axis in ICs and leads to unregulated cell growth in TSC cystogenesis

Funding

  • Other NIH Support