V1Rexpressing

V1Rexpressing refers to cells that express vomeronasal receptor type 1 (V1R) genes, a family of G protein–coupled receptors involved in pheromone detection. V1Rs are found in the vomeronasal organ (VNO) of many terrestrial vertebrates and contribute to social and reproductive behaviors by sensing chemical cues that are not typically detected by the main olfactory system.

V1R genes form a large, rapidly evolving multigene family. In many species, a significant portion of V1R genes can be functional while others exist as pseudogenes, reflecting evolutionary changes in pheromone communication. The V1R gene repertoire varies considerably across taxa, correlating with differences in mating systems and ecological niches. In the VNO, V1R-expressing neurons typically employ monoallelic, mono-receptor expression, a pattern described as one neuron–one receptor. Each neuron expresses a single V1R allele, and the axons of neurons expressing the same receptor converge onto specific glomeruli in the accessory olfactory bulb.

Anatomically, V1R-expressing neurons reside predominantly in the apical layer of the vomeronasal sensory epithelium and couple to the G protein Gαi2. Activation of a V1R by its ligand initiates a signaling cascade involving phospholipase Cβ2 and downstream calcium influx through channels such as TRPC2, culminating in neuronal excitation and transmission of a pheromonal signal to higher brain centers.

Ligands for V1Rs are diverse and include a range of semiochemicals, including some sulfated steroids and other small molecules. The study of V1Rexpressing cells provides insight into how chemical communication shapes behavior, species specificity, and evolution of the vertebrate pheromone system.