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.