Olfr

Olfr is the standard prefix used in the mouse genome to designate olfactory receptor genes. The Olfr gene family encodes a large collection of G protein–coupled receptors expressed in the sensory neurons of the main olfactory epithelium. The naming convention is maintained by mouse genome databases, with each gene labeled Olfr followed by a numeric identifier.

Olfactory receptors bind volatile odorant molecules. In vertebrates, they are seven‑transmembrane domain GPCRs that activate a G protein cascade, typically Golf, leading to increased cAMP and opening of cyclic nucleotide–gated channels. The resulting depolarization of olfactory sensory neurons triggers signals that are relayed to the olfactory bulb, contributing to odor perception and discrimination.

Genomic organization and expression: The Olfr genes form a very large multigene family, distributed in clusters across the genome. They arise and diversify mainly through gene duplication and sequence divergence. A substantial fraction of Olfr loci are pseudogenes in some strains, reflecting ongoing evolution of the olfactory repertoire. In mature olfactory neurons, typically only one Olfr gene is expressed, a selection that helps establish precise neural wiring to specific glomeruli in the olfactory bulb.

Diversity, evolution, and species differences: The Olfr repertoire in mice is extensive, with hundreds to more than a thousand functional genes reported across strains, whereas humans possess a smaller set of functional olfactory receptor genes and a larger number of pseudogenes. Across species, odorant receptor repertoires correlate with ecological niches and dietary needs, illustrating rapid evolution of smell genes.

Research context: Olfr genes are central to studies of olfactory coding, genome evolution, and sensory biology. Modern approaches map receptor–odorant interactions, expression patterns, and neural circuitry to understand how odor identity is represented in the brain.