Dissecting hypertonicity- and NFAT5-dependent gene expression programs in mpkCCD cells.

The corticomedullary osmotic gradient between renal cortex and medulla induces a specific spatial gene expression pattern. The factors controlling these differences have not been fully addressed. A hypertonic environment leads to the activation of nuclear factor of activated T-cells 5 (NFAT5), which regulates the expression of osmoprotective genes. While NFAT5 function under hypertonic conditions has been extensively studied, its contribution to basal gene regulation remains unclear. We used murine principal kidney cortical collecting duct (mpkCCD) cells, induced functional deletion of NFAT5, and performed gene expression profiling to identify genes that are differentially expressed under isotonic and hypertonic cell culture conditions. Hypertonic stress induced extensive transcriptional changes in control cells, which were markedly altered in NFAT5-deficient cells. Furthermore, a comparison of the mpkCCD transcriptomes with gene expression profiles from the renal cortex and inner medulla of control and principal cell-specific NFAT5 knockout mice revealed a partial overlap in hypertonicity-associated and NFAT5-dependent gene expression patterns. In both conditions, the expression of known NFAT5 target genes, like Aqp2 and Ranbp3l, was downregulated. These findings support the use of mpkCCD cells as a complementary model for studying NFAT5-associated gene regulation under controlled in vitro conditions.