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Kidney Week

Abstract: FR-OR26

Kidney Tubular YAP Controls the Expression of Collecting Duct Aquaporins and Water Homeostasis

Session Information

Category: Fluid, Electrolytes, and Acid-Base Disorders

  • 1101 Fluid, Electrolyte, and Acid-Base Disorders: Basic

Author

  • Xia, Yin, The Chinese University of Hong Kong Faculty of Medicine, Hong Kong, China
Background

Final urine volume and concentration are defined by water reabsorption through the water channel proteins aquaporin (AQP)-2, -3 and -4 in the collecting duct. However, the transcriptional regulation of these AQPs is not well understood. The Hippo/YAP pathway plays an important role in organ size control and tissue homeostasis. When the Hippo pathway including the Mst1/Mst2 kinases is inhibited, YAP is activated and functions as a transcription co-activator. Our previous work revealed a pathological role of tubular YAP activation in chronic kidney disease, but the physiological role of YAP in the kidney remains to be established.

Methods

Tubule-specific Yap knockout (Yap cKO) mice were generated by crossing Yapf/f mice with Ksp-Cre mice. Tubule-specific Mst1/Mst2 double (dKO) and Mst1/Mst2/Yap triple (tKO) mice were generated by crossing Mst1f/f;Mst2f/f or Mst1f/f;Mst2f/f;Yapf/f mice with Ksp-Cre mice respectively. Primary mouse medullary collecting duct cells were isolated from control and Yap cKO mice. RNA sequencing was performed on the medullae of control and Yap cKO mice at 6 weeks of age. ChIP-qPCR was performed using an YAP antiboty to determine whether YAP binds to the promotors of the Aqp2 and Aqp4 genes. Immunoprecipitation experiments were carried out to examine the interactions of YAP and GATA2, GATA3 or NFATc1.

Results

Tubule-specific Yap knockout mice showed increased urine output and decreased urinary osmolality. Decreases in Aqp2, -3 and -4 mRNA and protein abundance in the kidney were evident in Yap knockout mice. Analysis of Mst1/Mst2 double knockout and Mst1/Mst2/Yap triple knockout mice showed that expression of Aqp2 and Aqp4 but not Aqp3 was dependent on YAP. Furthermore, YAP was recruited to the promoters of the Aqp2 and Aqp4 genes and stimulated their transcription. Interestingly, YAP was found to interact with transcription factors GATA2, GATA3 and NFATc1. These three factors promoted Aqp2 transcription in a YAP dependent manner in collecting duct cells. These three factors also promoted Aqp4 transcription whereas only GATA2 and GATA3 enhanced Aqp3 transcription.

Conclusion

Our results suggest that YAP promotes Aqp2 and Aqp4 transcription, interacts with GATA2, GATA3 and NFATc1 to control Aqp2 expression, while Aqp-2, -3 and -4 exploit overlapping mechanisms for their baseline transcriptional regulation.

Funding

  • Government Support – Non-U.S.