GYS1 (glycogen synthase 1) is the rate-limiting enzyme catalyzing glycogen biosynthesis by transferring glucose units from UDP-glucose to the non-reducing end of alpha-1,4-glucan chains 1. Beyond its canonical cytoplasmic role in glycogen metabolism, GYS1 functions as a nucleocytoplasmic shuttling protein that dynamically reorganizes into nuclear biomolecular condensates under glycogen depletion conditions, where it complexes with the transcription factor NONO/p54 to regulate myogenic gene expression during muscle differentiation 2. Pathologically, GYS1 mutations cause polyglucosan storage myopathies affecting skeletal and cardiac muscle, presenting with myopathy, cardiomyopathy, arrhythmia, and conduction abnormalities 3. Additionally, GYS1 is associated with metabolic cardiomyopathies among inherited carbohydrate metabolism disorders 1. Emerging evidence reveals context-dependent roles in disease: GYS1 promotes nuclear factor kappa B signaling in cancer-associated fibroblasts to enhance anti-PD-1 immunotherapy response 4, while forming a positive feedback loop with p53 in ovarian clear cell carcinoma that drives platinum chemoresistance through glycogen-mediated NADPH production 5. GYS1 also appears as a biomarker in non-small cell lung cancer extracellular vesicles 6. These findings demonstrate GYS1's multifaceted roles spanning metabolic homeostasis, transcriptional regulation, and cancer biology.