DYRK1A Overexpression Drives Muscle Wasting by Impeding Myogenesis via a USP7‐Axin1‐β‐Catenin Regulatory Axis in Mice

ABSTRACT Muscle wasting, characterized by loss of muscle mass and strength, severely impacts patient quality of life and is associated with numerous chronic diseases and aging. The molecular mechanisms are complex, involving protein synthesis/degradation imbalance. Dual‐specificity tyrosine phosphorylation‐regulated kinase 1A (DYRK1A) and ubiquitin‐specific peptidase 7 (USP7) have diverse cellular roles, but their coordinated function in skeletal muscle homeostasis remains poorly understood. DYRK1A overexpression in vivo induced muscle atrophy phenotypes, including reduced muscle mass, grip strength, fiber cross‐sectional area (CSA), altered fiber type composition, and neuromuscular junction integrity, accompanied by elevated atrophy markers: muscle atrophy F‐box protein (Atrogin‐1), muscle ring finger 1 (MuRF‐1), myostatin and suppressed myogenic markers: myoblast determination protein 1 (MyoD), myogenin (MyoG), myocyte enhancer factor 2C (Mef2c), myogenic factor 5 (Myf5). Conversely, pharmacological inhibition of DYRK1A with Harmine ameliorated these atrophy phenotypes in transgenic DYRK1A overexpressing (TgD) mice. In vivo, USP7 deficiency resulted in similar muscle wasting phenotypes. In vitro, DYRK1A overexpression or USP7 overexpression inhibited C2C12 myoblast proliferation and differentiation, effects rescued by Wnt3a treatment or USP7 knockdown, respectively. Mechanistically, DYRK1A activity suppressed active β‐catenin levels. USP7 was found to interact with and deubiquitinate axis inhibition protein 1 (Axin1), leading to its stabilization. Knockdown of USP7 increased Axin1 ubiquitination and degradation, thereby promoting β‐catenin signaling and myogenesis, counteracting the effects of DYRK1A. Our findings reveal a novel signaling axis where DYRK1A and USP7 cooperatively suppress Wnt/β‐catenin signaling to promote muscle wasting. DYRK1A likely acts upstream, potentially phosphorylating pathway components, whereas USP7 stabilizes the β‐catenin destruction complex scaffold protein Axin1 through deubiquitination. This coordinated action inhibits myogenesis and activates atrophy pathways. Targeting DYRK1A or USP7 could represent promising therapeutic strategies for muscle wasting disorders.