Myogenic Protein Interactions in Rhabdomyosarcoma

Abstract

Rhabdomyosarcoma (RMS), a pediatric soft tissue sarcoma, is characterized by impaired myogenic differentiation and uncontrolled proliferation, often driven by dysregulated transcriptional and signaling networks. In this thesis, we unveil the first comprehensive protein interactomes of MEF2A and β-catenin—two pivotal regulators of skeletal myogenesis and oncogenesis—within RMS subtypes using nanobody-mediated affinity purification coupled with high-resolution mass spectrometry. Strikingly, despite reduced MEF2A expression in RMS cells, RD cells paradoxically exhibited elevated transcriptional activity, implicating compensatory post- translational modifications or unique cofactor interactions. In contrast, β-catenin activity was nearly abolished in the aggressive RH30 subtype, suggesting Wnt pathway evasion and reliance on alternative oncogenic circuits. Interactome mapping revealed subtype-specific regulatory landscapes: RD-derived MEF2A associated with splicing and transcriptional machinery, while RH30 networks were dominated by chromatin remodelers and epigenetic regulators. β-catenin’s interaction profile likewise diverged, linking to tumor-suppressive pathways in RD cells but shifting toward mitotic and nuclear export regulators in RH30. Enrichment analyses identified novel protein hubs—such as TRIM32, HDAC1, XPO1, and RACK1—that modulate gene expression, RNA metabolism, and cell cycle control, and may represent uncharted therapeutic nodes.