MSI1 (musashi RNA binding protein 1) is an RNA-binding protein that regulates target mRNA expression primarily through translational control. MSI1 binds specific RNA sequences including the pattern 5'-[GA]U(1-3)AGU-3' and directly interacts with 3' untranslated regions of target mRNAs to modulate their translation efficiency 12. MSI1 plays critical roles in stem cell biology across multiple tissues. In intestinal stem cells, MSI1 expression is maintained during fatty acid oxidation-dependent renewal 3. In embryonic stem cells, MSI1 and its short C-terminal variants regulate pluripotency states and early embryonic development, with roles in DNA-damage repair 4. MSI1 also promotes pro-neural reprogramming, primarily inducing switches toward early stem-like cells 5. Clinically, MSI1 dysregulation associates with multiple malignancies. MSI1 is highly expressed in osteosarcoma, where knockdown inhibits proliferation via p21/p27 upregulation 2. In breast cancer, MSI1 mediates alternative splicing of ALDOA to promote tamoxifen resistance through enhanced translation and mTOR pathway activation 1. MSI1 and HER2 co-expression correlate with unfavorable prognosis in mammary Paget's disease 6. In glioma, cytoplasmic MSI1 promotes angiogenesis and correlates with tumor grade 7. Additionally, ZIKV neurotropism involves MSI1-mediated mechanisms relevant to Alzheimer's disease pathogenesis 8.