SMAD1 is a transcriptional modulator that plays crucial roles in bone morphogenetic protein (BMP) signaling pathways and cellular regulation. Upon BMP ligand binding, SMAD1 is phosphorylated by activated BMP type I receptors and associates with SMAD4 to form heteromeric complexes that translocate to the nucleus and function as transcription factors 1. These complexes recognize specific DNA sequences to modulate gene expression in various cellular processes including osteogenesis, vascular remodeling, and myogenic differentiation. SMAD1 promotes osteogenic differentiation, as its downregulation through m6A methylation modifications contributes to postmenopausal osteoporosis 2. In vascular biology, high fluid shear stress suppresses SMAD1 activity through KLF2-BMPER signaling, facilitating arterial outward remodeling 3. SMAD1 also negatively regulates myogenic differentiation of mesoangioblasts, where its inhibition enhances muscle regeneration potential 4. Additionally, SMAD1 exhibits oncogenic properties in glioblastoma by sequestering p300 from p53, reducing p53 acetylation and promoting tumorigenicity and chemoresistance 5. SMAD1 expression is altered in various diseases, being decreased in diabetic nephropathy 6 and pulmonary hypertension associated with congenital heart disease 7, suggesting its potential as a disease biomarker.