Segment specific loss of NFAT5 function in the kidneys
Nuclear factor of activated T-cells 5 (NFAT5) is a transcription factor known for its role in osmotic stress adaptation in the renal inner medulla, due to osmotic gradient that is generated between renal cortex and renal inner medulla. However, its broader implications in kidney injury and chronic kidney disease (CKD) are less understood. Here we used two different Cre deleter mice (Ksp1.3-Cre and Aqp2-Cre) to generate tubule segment and even cell type specific NFAT5 deficient mice in the principal cells of the collecting duct (CD) and in the distal nephron starting in the TAL up to the CD and performed extensive gene expression profiling. In both Nfat5 knockout models, we observed massive changes in gene expression pattern, with heightened inflammatory responses and renal injury, culminating in renal fibrosis. Interestingly, inflammatory responses and fibrosis were much more prominent in the Aqp2Cre+/-Nfat5fl/fl mice that lack NFAT5 only in the collecting duct. By analyzing gene expression in the medullary and cortical regions of the kidney separately, we confirmed that the loss of NFAT5 results in kidney injury that extends beyond hypertonic areas. The correlation between the levels of inflammatory response, injury severity, and fibrosis indicates that cytokines are key mediators of stress signals in the kidney. Thus, NFAT5 is essential not only for adapting to osmotic stress but also for regulating cytokine signaling. Overall design: To explore the impact of spatial Nfat5-KO, we compared transcriptomic data from two different Nfat5-KO mouse models and distinguished between cortex and inner medulla. The first transgenic model involved a knockout driven by the Aqp2-promoter, causing Nfat5-KO in the principal cells of the collecting duct (CD). The second model used a knockout driven by the Ksp-promoter, leading to Nfat5-KO in the distal nephron starting in the TAL up to the CD. We performed differentially expression analyses using data from RNA-seq of renal cortex (CTX) and inner medulla (IM) of control mice (4 from Aqp2-Cre+/-; 4 from  Nfat5fl/fl, 4 from WT) and 6 from the  in the distal nephron (TAL up to the CD) Nfat5-KO mice (KspCre+/-Nfat5fl/fl). The RNA-seq data from Nfat5-KO in the principal cells of the CD (Aqp2Cre+/-Nfat5fl/fl) and control (Aqp2-Cre+/-) were collected in a previous study (GSE195881).