TRAPPC2 encodes Sedlin, a critical component of the trafficking protein particle (TRAPP) complex that regulates vesicular transport from the endoplasmic reticulum to the Golgi apparatus. TRAPPC2 functions as an adaptor protein, binding to TRAPPII-specific subunit TRAPPC9 and TRAPPIII-specific subunit TRAPPC8 to facilitate formation of mammalian TRAPPII and TRAPPIII complexes 1. The protein is essential for proper export of type II collagen (COL2A1) from the endoplasmic reticulum, with TRAPPC2 deficiency leading to decreased COL2A1 expression and impaired collagen II secretion 23. Loss-of-function mutations in TRAPPC2 cause X-linked spondyloepiphyseal dysplasia tarda (SEDT), a skeletal disorder characterized by defective vertebral bodies and epiphyses of long bones, resulting in short stature and early joint degeneration 43. Disease-causing variants include missense mutations, deletions, and splice site mutations that disrupt protein function and membrane trafficking 145. TRAPPC2 knockdown in cellular models causes Golgi fragmentation, demonstrating its importance in maintaining normal Golgi dynamics and membrane trafficking processes 6.