OR5I1 is an olfactory receptor that functions as a G protein-coupled receptor involved in odorant sensing and sensory perception of smell 1. The gene encodes a plasma membrane protein that participates in signal transduction pathways characteristic of the olfactory receptor family [GO annotations]. OR5I1 exhibits evidence of positive selection in human populations, with derived alleles segregating at relatively high frequencies across diverse populations 1. Molecular structural analysis suggests that nonsynonymous polymorphisms in OR5I1 may alter its functional binding properties for odorant ligands 1. Beyond olfactory function, OR5I1 is upregulated in human spermatogonial stem cells, suggesting potential roles in testicular development and spermatogenesis 2. Notably, OR5I1 functions as a tumor suppressor in hepatoblastoma, where it influences hepatoblastoma cell growth 3. These findings indicate OR5I1 has evolved under adaptive pressure and possesses pleiotropic functions extending beyond classical olfactory sensing to reproductive development and cancer biology.