MN1 is a transcriptional regulator essential for craniofacial and skeletal development. During palate development, MN1 specifically regulates TBX22 expression and is required for growth and medial fusion of palatal shelves [UniProt]. MN1 promotes osteoblast maturation and normal function of membranous skull bones, including expression of the osteoclastogenic cytokine RANKL [UniProt]. The gene participates in vitamin D receptor signaling and cell cycle regulation at the G1/S transition [GO Annotations]. Clinically, MN1 alterations are associated with multiple disease contexts. MN1 C-terminal truncation mutations cause MCTT syndrome, characterized by distinctive craniofacial and oral anomalies, with phenotypes differing by variant location 1. In the nervous system, MN1 alterations define distinct tumor entities: CNS high-grade neuroepithelial tumors with MN1 alteration (CNS HGNET-MN1) 2 and astroblastoma, where MN1-BEND2 and MN1-CXXC5 fusions converge on shared transcriptional networks to transform ventral telencephalon neural progenitors through OLIG2-dependent mechanisms and PDGFRα pathway activation 3. MN1:PATZ1 fusions define additional molecularly distinct neuroepithelial tumors with intermediate prognosis 4. Additionally, incomplete penetrance of MN1 pathogenic variants in neurodevelopmental disorders has been documented, complicating genetic interpretation 5. In acute myeloid leukemia, elevated MN1 expression occurs but lacks prognostic value 6.