MSX2 is a homeodomain transcription factor that functions as a transcriptional repressor in skeletal development and differentiation. In osteoblasts, MSX2 represses alkaline phosphatase (ALPL) promoter activity and suppresses osteocalcin FGF response element-driven transcription 1, antagonizing stimulatory effects of other transcription factors on osteogenic gene expression. MSX2 directly binds homeodomain-response elements in target promoters, including the ALPL and enamelin (Enam) promoters 1. Beyond bone development, MSX2 regulates vascular calcification by controlling osteogenic marker expression (Runx2 and Msx2 itself) downstream of β-catenin signaling 23. In trophoblast development, MSX2 serves as a downstream effector of SP6, regulating cytotrophoblast fate decisions and trophoblast stem cell establishment 4. MSX2 also regulates endogenous retrovirus-derived enhancers in human trophoblast stem cells, functioning as a transcriptional repressor of syncytiotrophoblast genes 5. In osteoclast biology, myeloid-specific MSX2 promotes osteoclast fusion by protecting the transcription factor PU.1 from degradation, with MSX2 deficiency reducing bone resorption 6. Clinically, MSX2 mutations cause craniosynostosis and parietal foramina, highlighting its essential role in craniofacial morphogenesis 7.