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Abstract: TH-PO895

HIF-Stabilization Drives Expression of MUC1 Pathogenic Variants in Human Renal Tubular Cells

Session Information

Category: CKD (Non-Dialysis)

  • 2201 CKD (Non-Dialysis): Epidemiology‚ Risk Factors‚ and Prevention

Authors

  • Naas, Stephanie, Universitatsklinikum Erlangen Medizinische Klinik 4 Nephrologie und Hypertensiologie, Erlangen, Bayern, Germany
  • Krüger, René, Universitatsklinikum Erlangen Medizinische Klinik 4 Nephrologie und Hypertensiologie, Erlangen, Bayern, Germany
  • Knaup, Karl Xaver, Universitatsklinikum Erlangen Medizinische Klinik 4 Nephrologie und Hypertensiologie, Erlangen, Bayern, Germany
  • Naas, Julia, Center for Integrative Bioinformatics Vienna (CIBIV), Max Perutz Labs, University of Vienna and Medical University of Vienna, Vienna, Austria
  • Grampp, Steffen, Universitatsklinikum Erlangen Medizinische Klinik 4 Nephrologie und Hypertensiologie, Erlangen, Bayern, Germany
  • Schiffer, Mario, Universitatsklinikum Erlangen Medizinische Klinik 4 Nephrologie und Hypertensiologie, Erlangen, Bayern, Germany
  • Wiesener, Michael Sean, Universitatsklinikum Erlangen Medizinische Klinik 4 Nephrologie und Hypertensiologie, Erlangen, Bayern, Germany
  • Schödel, Johannes, Universitatsklinikum Erlangen Medizinische Klinik 4 Nephrologie und Hypertensiologie, Erlangen, Bayern, Germany
Background

Various genetic alterations in the Mucin1 (MUC1) gene predispose to the development of chronic kidney disease. These variations comprise both the frequent GWAS-identified polymorphism rs4072037 that alters splicing of MUC1 mRNA but also ultra-rare autosomal-dominant inherited mutations which lead to expression of a deleterious frameshift (fs) protein causing autosomal dominant tubulointerstitial kidney disease (ADTKD-MUC1). Furthermore, the length of a region with a variable number of tandem repeats (VNTR) within the second exon of the MUC1 gene is associated with markers of kidney function. Hence, MUC1 presents a bona fide kidney disease gene. However, regulatory mechanisms influencing expression of MUC1 in the kidney are still poorly defined.

Methods

Primary renal tubular cells were isolated from kidneys of a large cohort of patients undergoing tumor nephrectomy or from the urine of ADTKD-MUC1 patients. Different pharmacological compounds causing stabilization of hypoxia-inducible transcription factors (HIFs) or hypoxia were used to investigate the effect of HIF on the expression of MUC1 and MUC1 pathogenic variants. Expression of MUC1 mRNA including splice variants was analysed by qPCR or RNA-sequencing. Wild-type MUC1 and fs-protein were detected by Immunoblotting.

Results

Using the Assay for Transposase-Accessible Chromatin with high-throughput sequencing and Chromatin Immunoprecipitation DNA-sequencing, we identified a regulatory, hypoxia-responsive element in the promoter-proximal region of MUC1, which drives MUC1 expression upon stabilization of HIF. HIF induces mRNA expression of wild-type MUC1 but also of the harmful splice-, VNTR-, and frameshift variants when tubular cells where exposed to hypoxia or novel prolyl-hydroxylase inhibitors to stabilize HIF.

Conclusion

In this study, we demonstrate a functional link between the regulation of MUC1 expression and the hypoxia-inducible transcription factor pathway in human renal tubular cells. In the context of the recent introduction of HIF-stabilizing substances for the treatment of renal anemia and the evidence for MUC1 pathogenic variants in causing kidney disease, our results should be considered when selecting patients for the treatment with novel HIF-stabilizing agents.