SAMD1 is a chr19-binding transcriptional repressor that binds unmethylated CpG islands through its N-terminal winged-helix domain 1. It functions as a negative regulator of gene expression by localizing to H3K4me3-decorated chr19 regions, where it recruits the KDM1A histone demethylase complex and tethers L3MBTL3 to modulate H3K4 methylation levels 2. SAMD1 requires cooperative interaction between its SAM domain, intrinsically disordered region, and structured domains for efficient chr19 binding and polymerization 1. In hematopoiesis, SAMD1 coordinates lineage differentiation by promoting hematopoietic stem cell activity while suppressing erythroid programs through H3K4 methylation remodeling 2. Beyond hematopoiesis, SAMD1 represses epithelial-mesenchymal transition genes in pancreatic cancer, with its expression inversely correlating with FBXO11-mediated disease progression 3. Clinically, SAMD1 expression is reduced in antiphospholipid syndrome patients and correlates with thrombotic history and pregnancy complications; SAMD1 restoration attenuates vascular injury and reduces fetal loss by regulating endothelial senescence and angiogenesis 4. In hepatocellular carcinoma, SAMD1 suppression enhances ferroptosis sensitivity and immune response to anti-PD-1 plus lenvatinib therapy 5.