Elucidation of the distal convoluted tubule transcriptome identifies new candidate genes involved in renal Mg²⁺ handling

The kidney plays a key role in the maintenance of Mg²⁺ homeostasis. Specifically, the distal convoluted tubule (DCT) is instrumental in the fine-tuning of renal Mg²⁺ handling. In recent years, hereditary Mg²⁺ transport disorders have helped to identify important players in DCT Mg²⁺ homeostasis. Nevertheless, several proteins involved in DCT-mediated Mg²⁺ reabsorption remain to be discovered, and a full expression profile of this complex nephron segment may facilitate the discovery of new Mg²⁺-related genes. Here, we report Mg²⁺-sensitive expression of the DCT transcriptome. To this end, transgenic mice expressing enhanced green fluorescent protein under a DCT-specific parvalbumin promoter were subjected to Mg²⁺-deficient or Mg²⁺-enriched diets. Subsequently, the Complex Object Parametric Analyzer and Sorter allowed, for the first time, isolation of enhanced green fluorescent protein-positive DCT cells. RNA extracts thereof were analyzed by DNA microarrays comparing high versus low Mg²⁺ to identify Mg²⁺ regulatory genes. Based on statistical significance and a fold change of at least 2, 46 genes showed differential expression. Several known magnesiotropic genes, such as transient receptor potential cation channel, subfamily M, member 6 (Trpm6), and Parvalbumin, were upregulated under low dietary Mg²⁺. Moreover, new genes were identified that are potentially involved in renal Mg²⁺ handling. To confirm that the selected candidate genes were regulated by dietary Mg²⁺ availability, the expression levels of solute carrier family 41, member 3 (Slc41a3), pterin-4 α-carbinolamine dehydratase/dimerization cofactor of hepatocyte nuclear factor-1α (Pcbd1), TBC1 domain family, member 4 (Tbc1d4), and uromodulin (Umod) were determined by RT-PCR analysis. Indeed, all four genes show significant upregulation in the DCT of mice fed a Mg²⁺-deficient diet. By elucidating the Mg²⁺-sensitive DCT transcriptome, new candidate genes in renal Mg²⁺ handling have been identified.