YY1 regulates vascular resistance and blood pressure dynamics through epigenetic control of m6A RNA modifications in VSMCs

Aims Recent GWAS analysis has identified YY1 as a novel locus associated with blood pressure traits; however, whether YY1 directly controls vasoreactivity remains unknown. The principal function of vascular smooth muscle cells (VSMCs) is to contract, which is essential for regulating vascular tone, blood flow, and blood pressure. We hypothesized that YY1, a transcription factor, facilitates vascular function by epigenetically regulating gene expression in VSMCs. Methods and Results The effects of VSMC-specific YY1 loss were studied in mice. Lineage tracing, calcium imaging, and wire myography were performed to assess vasoreactivity. Genome-wide analysis through RNA-seq, ChIP-seq, m6A-seq, RNA immunoprecipitation, and transcript stability assays were conducted to evaluate gene expression and regulation. Co-immunoprecipitation was performed to study interactions between YY1 and chromatin regulators. AAV-mediated SM22-specific gene delivery was used to rescue vascular function in vivo. Contractile VSMCs were differentiated from human embryonic stem cells for in vitro experiments. Hypertension was induced in vivo using salt and L-NAME treatments. We demonstrate that vascular contraction and blood pressure are significantly reduced in Myh11CreER;Yy1fl/fl mice. YY1 does not regulate VSMC proliferation, survival, calcium entry, or membrane polarization in homeostasis. Integrative analyses of transcriptomics, epitranscriptomics, and epigenetics identified Mettl3 as a putative downstream target of YY1. Like YY1 loss-of-function, impaired vascular contraction and reduced blood pressure were observed in Myh11CreER;Mettl3fl/fl mice. Mylk2, Tgfb2, and Myh11 were significantly downregulated after genetic ablation of Yy1 or Mettl3 in VSMCs. Further analysis showed that Mettl3-mediated m6A mRNA methylation stabilizes the transcripts of these genes, possibly through the m6A reader IGF2BP1. AAV-mediated, VSMC-specific Mettl3 gene delivery significantly improved vascular contractility in Yy1-deficient mice, functionally confirming Mettl3 as a direct downstream target of YY1. Mechanistically, YY1 binds to the Mettl3 promoter near regions of H3K4 trimethylation and activates Mettl3 transcription by recruiting Set1A-Wdr82 complex for H3K3me3 deposition. Both Myh11CreER;Yy1fl/fl and Myh11CreER;Mettl3fl/fl mice exhibited delayed onset of hypertension. Conclusions YY1 maintains vascular contraction and regulates blood pressure by stabilizing Mylk2, Tgfb2, and Myh11 transcripts through the activation of Mettl3 transcription in VSMCs. These findings provide novel insights into the epigenetic control of VSMC epitranscriptomes and unravel a new mechanism underlying VSMC-mediated vasoconstriction through the YY1/Mettl3 regulatory axis. Additionally, our results demonstrate a clinically relevant role for the YY1/Mettl3 axis in mitigating hypertension and regulating blood pressure under both normal and hypertensive conditions.