Single Cell RNA-Sequencing Uncover the Molecular Determinants of Sexual Dimorphism in Renal Potassium Regulation
Authors: Jung Hyun Jung , Grimm Rick , Welling Paul , Al-Qusairi Lama 
Published: May 2024

Background: Women are more prone to hypokalemia than men, which exposes them to a higher risk of hypokalemia-induced disorders. We have previously shown the response to potassium (K+) deficiency in mice parallels the human condition, with females exhibiting more severe hypokalemia than males upon dietary K+ deficiency. Here, we investigated the molecular underpinnings of this sexual dimorphism. Methods: The renal adaptations to K+ deficiency were analyzed in Wild-type (WT) male and female mice. Animals were randomized to a control or K+-free diet for 8 days. The transcriptional landscape of control and K+-deprived kidneys was investigated using single nucleus RNA-Seq (snRNA-Seq). At least 5000 nuclei/sample were analyzed. Results: We found female susceptibility to hypokalemia originates from renal K+ loss. Cell type-dependent transcriptome profiling of whole kidneys revealed that all nephron segments undergo transcriptional reprogramming in response to K+ deprivation, with generally more differentially expressed genes (DEGs) in females than males. The proximal tubules (PTs) exhibit major transcriptional reprogramming with 747 DEGs in females compared to 213 DEGs in males. Pathway enrichment analysis of the DEGs in the PT revealed the response to K+ deficiency involves several regulatory mechanisms common to both sexes, such as monocarboxylic acid metabolic pathway and purine-containing compound metabolism. Among all the nephron segments, the connecting tubules (CNTs) exhibit striking sex-dependent changes in response to K+ deprivation with more DEGs in males (100) compared to females (67) despite the less severe hypokalemia in males. Pathway enrichment analysis of the DEGs in the CNT indicated the cytoskeleton and actin organization were mostly reprogrammed in females. In contrast, in male CNT, ion channel regulating pathways exhibited a more active reprogramming. In the CNT, transcript abundance of the Kl gene encoding for Klotho protein, a positive regulator of the K+ exit channel ROMK, was significantly decreased in K+-deprived males only. Similarly, Klotho protein was significantly reduced in response to K+ deprivation, specifically in males but not females. Confocal imaging confirmed decreased ROMK and Klotho in male CNT, consistent with more effcient K+ conservation in males than females. Conclusion: All nephron segments undergo transcriptional reprogramming in response to K+ deprivation, indicating the K+ response is generalized and not restricted to the distal nephron, as previously described. Among all the segments, the CNT exhibits a striking sex-dependent transcriptional reprogramming in response to K+ deficiency. The female susceptibility to hypokalemia results mainly from a less effcient reduction of ROMK-dependent K+ secretion in the CNT, leading to urinary K+ loss. DK054231, DK137331 and CNVA00060589. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.