ITM2A is a type II integral membrane protein with roles spanning skeletal development, immune regulation, and cancer biology. Primary Function: ITM2A functions as a marker of periosteal skeletal stem cells (P-SSCs) that display clonal multipotency and self-renewal capacity 1. The protein localizes to the Golgi apparatus and large cytoplasmic vesicles, with surface expression increasing upon T cell activation 2. Mechanism: ITM2A is induced during thymocyte positive selection and T cell activation 2, and modulates cellular responses through the Notch signaling pathway 3 and ERK signaling 4. Disease Relevance: ITM2A expression is downregulated in cervical cancer tissues and is associated with poor survival; overexpression restores cisplatin sensitivity 3. Similarly, low ITM2A expression correlates with imatinib resistance in chrX myeloid leukemia 4. ITM2A polymorphisms on the X chromosome X associated with autoimmune thyroid disease susceptibility in children 5. Elevated urinary ITM2A mRNA distinguishes acute kidney allograft rejection from non-rejection 6. Clinical Significance: ITM2A represents an attractive therapeutic target for skeletal disorders through cellular therapy 1 and for overcoming chemotherapy resistance in hematologic and solid malignancies. Its expression in brain microvessels suggests potential application in brain drug delivery, though in vivo transcytosis requires further investigation 7.