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

Abstract

Background: 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.

Methods: 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 Mettl7a1 knockout mice. Endothelial METTL7A expression was restored using polymer-based nanoparticles delivering cadherin 5 (CDH5) promoter-driven METTL7A plasmids or VCAM-1 (vascular cell adhesion molecule-1)-targeted lipid nanoparticles delivering N1-methylpseudouridine-modified METTL7A mRNA.

Results: 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 KLF4 and NFKBIA 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 Mettl7a1 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 Mettl7a1^-/^- and ApoE^-/^- mice.

Conclusions: METTL7A is a mechanosensitive internal m⁷G methyltransferase that maintains endothelial homeostasis by stabilizing the anti-inflammatory transcripts KLF4 (Krüppel-like factor 4) and NFKBIA (NFKB inhibitor alpha). 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.