BCAP29 (B cell receptor-associated protein 29) is a membrane protein involved in intracellular protein trafficking and cellular regulation. The protein likely functions in anterograde transport of membrane proteins from the endoplasmic reticulum to the Golgi apparatus and may participate in CASP8-mediated apoptotic pathways [UniProt annotation]. BCAP29 is expressed across diverse tissues, including joint tissues (cartilage, bone, and synovial tissue) 1 and the ciliary body of the eye 2. In cancer biology, BCAP29 participates in the DUS4L-BCAP29 fusion transcript, which is generated through cis-splicing between adjacent genes 34. While initially identified in gastric and prostate cancers where it promotes cell growth and motility 5, this fusion transcript also exists in normal tissues at comparable expression levels and cannot serve as a cancer biomarker 3. Overexpression of DUS4L-BCAP29 enhances cell proliferation and motility even in non-cancerous cells 34. Genetically, BCAP29 variants are associated with osteoarthritis susceptibility. A genome-wide association study identified a knee osteoarthritis locus on chromosome 7 encompassing BCAP29 1, with evidence suggesting gene-gene interactions in hand osteoarthritis predisposition 6. Additionally, BCAP29 has been implicated in inflammatory bowel disease risk 7. Alternative splicing of BCAP29 is regulated by LGALS1 in lung cancer contexts 8.