Collecting Duct Gene Expression in a Mouse Vasopressin-Excess Model without Hyponatremia

Introduction. States of vasopressin excess can exist either with or without hyponatremia, depending on water intake. Here, we set up a mouse model of vasopressin-excess without hyponatremia to address the consequences of vasopressin excess that are independent of serum sodium. Methods. A mouse vasopressin-excess model was created by infusing desmopressin for 5 days without a forced water load. Control mice were infused with vehicle. Results. RNA-seq in microdissected cortical collecting ducts (CCDs) from vasopressin-excess mice showed significant changes in 153 transcripts including the expected increases in aquaporin-2 (AQP2) and AQP3 along with increases in several other targets of V2-receptor-mediated signaling in principal cells. In addition, there were decreases in abundances of many transcripts known to be targets of regulation by the Wnt/frizzled/β-catenin pathway. The vasopressin-excess model also manifested marked increases in phosphorylation of β-catenin at a known protein kinase A (PKA) site, viz. Ser552. CRISPR-mediated mutation of this PKA-target site in mice resulted in extensive changes in the transcriptomes of microdissected CCDs after desmopressin-infusion, heavily weighted toward increases in known transcriptional targets of the Wnt/β-catenin pathway. ATAC-seq in microdissected CCDs from DDAVP-infused mice revealed decreases in chromatin accessibility at promoters of many genes regulated in the Wnt/β-catenin pathway. Conclusion. We conclude that vasopressin-excess is associated with vasopressin/PKA-dependent repression of Wnt/Frizzled/β-catenin target gene expression, mediated in part by PKA-dependent phosphorylation of Ser552 of β-catenin. The repression is associated with decreasing chromatin accessibility in the promoter-TSS regions of target genes. The findings suggest that normonatremic vasopressin-excess is not necessarily benign.