OR1D4 is an olfactory receptor belonging to the OR1D subfamily, functioning as a seven-transmembrane G-protein coupled receptor (GPCR) involved in olfactory signal transduction 1. As a member of the human olfactory receptor family, OR1D4 is primarily expressed in the olfactory epithelium and exhibits ectopic expression in other tissues 1. The receptor demonstrates high sequence identity (>80%) with related OR1D subfamily members OR1D2 and OR1D5, sharing characteristic structural features including transmembrane domains that present technical challenges for proteomics-based identification 21. OR1D4 has documented protein-level evidence based on protein interaction data 1. Clinically, OR1D4 has been identified as involved in cancer-associated structural rearrangements. Recurrent intergenic gene fusions involving OR1D4 have been detected in breast cancer, where fusion-mediated regulatory repositioning may dysregulate neighboring genes 3. These findings suggest OR1D4's participation in cancer genomic instability, though the specific oncogenic mechanism requires further investigation. The olfactory receptor's role extends beyond sensory perception to multiple signaling pathways 1, indicating broader biological functions beyond its canonical role in smell detection.