Mechanosensitive Endothelial METTL7A Regulates Internal m⁷G mRNA Methylation and Protects Against Atherosclerosis.

Abstract

Internal N7-methylguanosine (m⁷G) is a recently identified chemical modification of mammalian mRNA. Although the epitranscriptome plays a key role in regulating RNA metabolism and cellular function, the specific contribution of internal m⁷G to cardiovascular disease remains unknown. Atherosclerosis preferentially develops at sites of disturbed blood flow, which promotes endothelial activation; however, whether internal m⁷G regulates endothelial mechanotransduction and atherogenesis remains unclear. We integrated epitranscriptomic profiling, human tissues, genetically modified mice, and targeted nanomedicine approaches to investigate the role of METTL7A (methyltransferase-like protein 7A), a putative internal m⁷G methyltransferase, in endothelial mechanobiology and atherosclerosis. Vascular endothelial cells were subjected to atheroprotective and atheroprone flow waveforms in vitro and in vivo. METTL7A function was assessed using RNA sequencing, liquid chromatography-tandem mass spectrometry, crosslinking immunoprecipitation sequencing, RNA stability assays, and a clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated-inspired RNA targeting system. METTL7A expression was examined in human coronary arteries with and without atherosclerosis. Atherosclerosis studies were conducted using global and endothelial-specific <i>Mettl7a1</i> knockout mice. Endothelial METTL7A expression was restored using polymer-based nanoparticles delivering CDH5 promoter-driven METTL7A plasmids or VCAM-1 (vascular cell adhesion molecule-1)-targeted lipid nanoparticles delivering N1-methylpseudouridine-modified METTL7A mRNA. Atheroprotective unidirectional flow significantly induced METTL7A expression, which promoted internal m⁷G methylation of endothelial transcripts without affecting cap-associated m⁷G. METTL7A preferentially bound AG-enriched motifs in protein-coding mRNAs and increased internal m⁷G methylation and stability of <i>KLF4</i> and <i>NFKBIA</i> transcripts, thereby supporting vascular homeostasis. Endothelial METTL7A expression was significantly reduced by disturbed blood flow and in human atherosclerotic lesions. Global or endothelial-specific loss of <i>Mettl7a1</i> exacerbated atherosclerosis in mice independent of serum lipid levels. Endothelial restoration of METTL7A through nanoparticle delivery of either a METTL7A plasmid or N1-methylpseudouridine-modified METTL7A mRNA markedly attenuated atherosclerotic lesion formation in <i>Mettl7a1</i>^<i>-</i><i>/</i>^<i>-</i> and <i>ApoE</i>^<i>-</i><i>/</i>^<i>-</i> mice. METTL7A is a mechanosensitive internal m⁷G methyltransferase that maintains endothelial homeostasis by stabilizing the anti-inflammatory transcripts KLF4 (Krüppel-like factor 4) and NFKBIA. Loss of METTL7A disrupts endothelial function and accelerates atherogenesis. Endothelial restoration of METTL7A through complementary targeted nanoparticle platforms significantly reduces atherosclerotic burden. These findings uncover a novel epitranscriptomic mechanism governing vascular health and position METTL7A as a promising therapeutic target for atherosclerotic cardiovascular disease.