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Abstract: PO0629

Transcriptomic Profiling of Thick Ascending Limb Cells In Vivo Reveals the Complex Network of Genes Regulated by Uromodulin

Session Information

  • CKD Mechanisms - 2
    October 22, 2020 | Location: On-Demand
    Abstract Time: 10:00 AM - 12:00 PM

Category: CKD (Non-Dialysis)

  • 2103 CKD (Non-Dialysis): Mechanisms

Authors

  • LaFavers, Kaice A., Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Khan, Shehnaz, Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Khan, Nida A., Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Apple, Laura, Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Micanovic, Radmila, Indiana University School of Medicine, Indianapolis, Indiana, United States
  • El-Achkar, Tarek M., Indiana University School of Medicine, Indianapolis, Indiana, United States
Background

Tamm-Horsfall Protein (THP or Uromodulin, gene: Umod) is a protein uniquely made in the kidney by cells of the thick ascending limbs (TAL) of the loop of Henle. We previously established that THP has protective biological functions. Furthermore, THP production is decreased with chronic kidney disease (CKD). It was suggested that the promoter region of the Umod can regulate other genes. THP deficiency itself could alter the expression of other genes. Here, we used an unbiased approach to study the effect of a deletion in the Umod promoter/gene and the resultant THP deficiency on the transcriptomic profile of TAL cells in vivo.

Methods

THP-/- mice resultant from deletion of exons 1-4 and part of the Umod promoter were used, along with THP+/+ controls. Immuno-fluorescence guided laser microdissection was performed to isolate TAL cells from the medulla of kidneys of THP-/- and THP+/+ mice. After RNA extraction, next generation RNA sequencing and transcriptomic analysis was performed.

Results

The transcriptomic profile of medullary TAL cells was comprehensively defined in vivo. 85% of the top 250 expressed genes were common between THP+/+ and THP-/- TAL cells. Overall, 33 protein-coding genes, including Umod, were differentially expressed (FDR<0.05). These encompassed genes with a variety of functions such as immunomodulation (Erdr1, Gp2), cytoskeletal/extracellular matrix fibers (Lama1, Cttnbp2) and signal transduction (Camk2b, Ptprn2). One down-regulated gene was a direct neighbor to the Umod locus (Gp2) on chromosome 7. However, many other affected genes were on different chromosomes. Bioinformatic analysis revealed that THP deficiency is associated with significant clustering of genes involved in connective tissue formation and activation or dysfunction of molecular mechanisms that could lead to fibrosis.

Conclusion

We delineated a comprehensive transcriptomic profile of TAL cells in vivo from mouse kidneys. Although highly expressed genes in TAL may not be altered by THP deficiency, many close and distant genes are regulated by the Umod locus or altered by the absence of THP. The absence of THP may also prime the TALs cells towards a fibrosis program. These findings may contribute to understanding the pathogenesis of CKD progression.

Funding

  • NIDDK Support