MID1 (midline 1) is an E3 ubiquitin ligase belonging to the TRIM family of proteins that plays crucial roles in embryonic development and cellular regulation 1. The protein localizes to microtubules and forms a complex with protein phosphatase PP2A catalytic subunit and its regulatory subunit alpha 4 1. MID1 functions by promoting ubiquitin-mediated proteasomal degradation of various substrates, including IGBP1, DPP4, and RIC8A 123. Loss-of-function mutations in MID1 cause X-linked Opitz syndrome, a rare disorder characterized by malformations of ventral midline structures including hypertelorism, hypospadias, and laryngo-tracheo-esophageal defects 45. Beyond developmental disorders, MID1 has pathological implications in other conditions including rheumatoid arthritis, where it promotes synovial cell proliferation and migration through DPP4 degradation 2, and osteoarthritis, where it regulates cartilage homeostasis via the RIC8A-p38 MAPK pathway 3. The protein's involvement in mTOR signaling and translational regulation positions it as a central cellular regulator with therapeutic potential for treating various diseases including cancer and neurodegenerative conditions 5.