NAT10-dependent ac4C mRNA modification programs fibroblast pathogenicity in systemic sclerosis.

Systemic sclerosis (SSc) is characterized by progressive fibrosis driven by persistent activation of dermal fibroblasts, yet the epigenetic and epitranscriptomic mechanisms sustaining fibroblast pathogenicity remain incompletely defined. Here, we investigated the role of N-acetyltransferase 10 (NAT10)-mediated N4-acetylcytidine (ac4C) RNA modification in fibroblast activation and fibrotic remodeling. Integrative analyses of single-cell transcriptomics, human SSc skin, in vitro assays, in vivo models, and fibroblast-specific knockout mice revealed that NAT10 is upregulated in pathogenic fibroblast populations and contributes to fibrotic progression. Genetic ablation or pharmacological inhibition of NAT10 attenuated fibroblast proliferation and extracellular matrix deposition across experimental systems. Multi-omics analyses identified COL11A1 and ZNF621 as downstream targets associated with NAT10, with site-specific ac4C modifications detected on both transcripts. Mechanistically, NAT10-dependent ac4C deposition was associated with increased mRNA stability and transcriptional output of these pro-fibrotic genes. Notably, suppression of ZNF621 partially reversed the pro-fibrotic phenotypes induced by NAT10 overexpression, supporting its functional relevance downstream. Together, these findings define an epitranscriptomic mechanism contributing to fibroblast activation in SSc and suggest that targeting the NAT10-ac4C axis may represent a potential therapeutic strategy for fibrotic disease.