Multi-omics reveals global signaling rewiring and identifies Activin A-induced dysregulation of FOS/Activator Protein 1 as a novel target in Fibrodysplasia ossificans progressiva

BackgroundFibrodysplasia ossificans progressiva (FOP) is caused by an activating mutation (p.R206H) in the type I BMP receptor ALK2, leading to heterotopic ossification (HO) in soft connective tissues. While aberrant Activin A-induced SMAD signaling is central in FOP pathogenesis, global signaling alterations remain poorly understood. MethodsWe performed phosphoproteomics, transcriptomics and biochemical analyses in mesenchymal cells (MSCs) overexpressing wild-type ALK2WT or mutant ALK2R206H receptors and in induced-MSCs derived from FOP patient iPSCs. Findings were validated in vivo using FOP-like mouse models and in vitro via pharmacological interventions. ResultsMulti-omics analyses revealed previously unrecognized signaling networks in ALK2R206H cells, including enhanced MAPK, mTOR, RUNX2 and RHO-mediated mechanotransduction pathways. Notably, we identified dysregulated Activator Protein-1 (AP-1) expression and function as a novel contributor to FOP. AP-1 factors were highly enriched in HO lesions in FOP-like animals. Pharmacological inhibition of AP-1 significantly reduced osteochondrogenic differentiation in vitro. ConclusionThis study highlights global signaling dysregulation in FOP and identifies AP-1 as a critical driver and potential therapeutic target for FOP.