Expression of pheromone receptor gene families during olfactory development in the mouse: expression of a V1 receptor in the main olfactory epithelium

Abstract

In the mouse, two large gene families, V1R and V2R, encoding putative pheromone receptors have been described. Studies have suggested a homotypic recognition role for V1Rs and V2Rs during development in the targeting of vomeronasal axons to specific sets of glomeruli in the accessory olfactory bulb (AOB). Analysis of the onset of expression of the V1R and V2R gene families in developing vomeronasal neurons using polymerase chain reaction and in situ hybridization now suggests that a role for these receptors in the organization of axon projections is only likely at the final stages of targeting within the AOB. Surprisingly, our studies reveal expression of a V1Rd receptor in scattered cells within the main olfactory epithelium, suggesting that limited pheromone detection may also take place in this structure. The pheromone sensory neurons of the vomeronasal system and the neuroendocrine gonadotrophin-releasing hormone (GnRH) neurons that regulate fertility both arise from progenitor cells of the nasal placode. The development of these two cell types is intimately linked, and the GnRH neuron population migrates into the forebrain during embryogenesis in close association with a subset of vomeronasal sensory axons; how GnRH neurons recognize this axon subset is unknown. We report selective expression of a V1Ra gene in the clonal NLT GnRH cell line, raising the possibility of a similar role for V1Rs or V2Rs in the directed migration of GnRH neurons. However, no expression of this gene or of other V1Rs and V2Rs is detectable at the cellular level in migrating GnRH neurons in the mouse.

Extreme variability among mammalian V1R gene families

“…Although it is quite likely that these V1R-like sequences function as receptors for external signals in the vomeronasal organ, it is possible that some of the sequences have taken on a novel function in a different organ in one or more species. For example, some human, goat, and mouse V1Rs have been suggested to function in the main olfactory epithelium rather than the vomeronasal organ (Rodriguez et al 2000;Wakabayashi et al 2002;Karunadasa et al 2006).…”

Expression of a vomeronasal receptor gene (V1r) and G protein α subunits in goat, Capra hircus, olfactory receptor neurons

“…Although it has been reported that V1rs are expressed on ORNs in some mammalian species such as humans, goats, and mice (Rodriguez et al, 2000;Wakabayashi et al, 2002;Karunadasa et al, 2006), the function of V1rs in mammalian ORNs still remains unclear. To investigate the characteristics of goat V1r-expressing ORNs we identified the G proteins expressed in gV1ra1-expressing ORNs in goat OE by double-label in situ hybridization.…”

“…Rodent OE has mainly four zones in which the expression patterns of different ORs are defined (Ressler et al, 1993). In mouse OE, V1r-expressing ORNs are distributed widely, but are more frequently distributed in the medial region, that is, zones 1 and 2 (Karunadasa et al, 2006). In this study we obtained olfactory tissues randomly from goat OE.…”

“…Recently, it has been reported that mouse V1rs are also expressed in a small subset of ORNs (Karunadasa et al, 2006), implying that V1rs on ORNs may function as chemoreceptors in a variety of mammals. Furthermore, human vomeronasal receptor (V1RL1) mRNA is also encoded in cDNA derived from the olfactory mucosa (Rodriguez et al, 2000).…”

Seasonal Variation in the Expression of Five Subtypes of Gonadotropin-releasing Hormone Receptor Genes in the Brain of Masu Salmon from Immaturity to Spawning

“…Interestingly, members of these two families have also been found to be expressed in small numbers in the olfactory epithelium of frogs (Xenopus laevis, Date-Ito et al, 2008), goats (Capra hircus, Wakabayashi et al, 2002;Wakabayashi et al, 2007), mice (Mus musculus, Karunadasa et al, 2006), and humans (Rodriguez et al, 2000). The phylogenetic diversity of these animals indicates that olfactory epithelial expression of V1R and V2R genes may be widespread among tetrapods, suggesting the existence of four classes of olfactory receptor neurons: those expressing ORs, TAARs, V1Rs, and V2Rs.…”