Deletion of Klotho enhancer deepens sexual dimorphism of gene expression without impacting female resistance to kidney injury [RNA exp1]

Sexual dimorphism in kidney injury markers, such as Klotho, is frequently underestimated or disregarded, as most of the preclinical research is done in male animals. Klotho is well-linked to renal health and its deletion in mice results in a severe accelerated aging-like phenotype and premature death. Here, we identified candidate Klotho enhancers and discovered their function using mice carrying deletions in the enhancer loci. Candidate Klotho enhancers were deleted using CRISPR/Cas9 genome editing. Warm ischemia-reperfusion surgery (IRI) was performed bilaterally to induce acute kidney injury and unilaterally in a fibrosis model. Using ChIP-seq and RNA-seq, we analyzed renal chromatin features and gene expression. ELISA and colorimetric assays were used to measure serum FGF23 and serum component levels. Removal of the enhancer caused more substantial reduction in Klotho mRNA levels in female mice compared to males (90 vs. 50%), supported by gene promoter marks remaining more pronounced in males. Weight, lifespan, and fertility of mice lacking the enhancers were not impacted. Only male mutant mice displayed higher Havcr1 expression after IRI than controls (mean 1048 vs. 231.4, p=0.0016). 28 days after unilateral IRI, only males displayed increased fibrosis markers, but with no difference between genotypes. Our findings reveal sexual dimorphism of Klotho gene expression and its enhancer regulation. Only male mutant mice were more susceptible to acute injury and the enhancer deletion had no impact on fibrosis. Additional investigation into the mechanisms governing Klotho regulation is imperative to reassess its effectiveness as a kidney injury marker.