The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
The supplied identifiers are internally consistent: Vmn2r73 denotes mouse vomeronasal type-2 receptor 73, encoded in Mus musculus and represented by UniProt accession A0A3B2WCZ5. Its supplied InterPro annotations—ANF-like ligand-binding receptor domain, class-C GPCR domain, nine-cysteine domain/superfamily, and calcium-sensing-receptor-related class-C GPCR domain—fit the established architecture of mammalian V2Rs. V2Rs are class-C, glutamate-receptor-like GPCRs with a large extracellular ligand-binding module and a seven-transmembrane signaling region (mohrhardt2018signaldetectionand pages 6-7, mohrhardt2018signaldetectionand pages 5-6).
However, the literature is very limited for this specific protein. Exact searches for “Vmn2r73” and “A0A3B2WCZ5,” including examination of recent mouse-vomeronasal single-cell studies, found no receptor-specific ligand, signaling assay, protein-localization experiment, axonal tracing, knockout, phenotype, or behavioral function. Consequently, Vmn2r73 should presently be annotated as an orphan, predicted sensory class-C GPCR. Most functional statements below are explicitly identified as V2R-family inference rather than direct Vmn2r73 evidence.
| Claim/attribute | Best conclusion | Evidence level | Key caveat |
|---|---|---|---|
| Identity and organism | Vmn2r73, UniProt A0A3B2WCZ5, is annotated as vomeronasal 2 receptor 73 from Mus musculus. | Direct UniProt annotation | Identity is based on the supplied UniProt, Ensembl, and MGI annotation; exact-symbol and accession searches found no contradictory literature or gene-specific paper. |
| Protein class and domains | Predicted class-C GPCR/V2R containing an extracellular ANF-like ligand-binding region, a nine-cysteine region, and a seven-transmembrane GPCR domain; the architecture is calcium-sensing-receptor-related. | Direct UniProt annotation, supported by V2R-family inference | The domains are database annotations rather than experimentally mapped features of Vmn2r73; V2Rs generally possess a large extracellular Venus-flytrap ligand-binding module and seven-transmembrane topology (mohrhardt2018signaldetectionand pages 6-7, mohrhardt2018signaldetectionand pages 5-6). |
| Molecular function | Most plausibly a sensory chemoreceptor that converts extracellular chemical-cue recognition into neuronal signaling. | V2R-family inference | No binding, activation, mutagenesis, or structural experiment was found for Vmn2r73 itself. |
| Ligand or substrate specificity | Unknown; Vmn2r73 remains an orphan receptor. Candidate cue classes for some V2Rs include peptides and proteins such as MHC-associated peptides, ESPs, and MUPs. | Unknown for Vmn2r73; V2R-family context | Candidate cue classes must not be assigned to Vmn2r73. Only a few V2Rs have receptor-level ligand evidence, and recombinant expression and deorphanization remain difficult (stempel2017comparativeanalysesof pages 21-24, mohrhardt2018signaldetectionand pages 5-6, mohrhardt2018signaldetectionand pages 8-8). |
| Tissue and cell localization | Predicted to be expressed in basal vomeronasal sensory neurons of the mouse vomeronasal organ, the canonical location of V2R-family expression. | V2R-family inference | No Vmn2r73-specific in situ hybridization, immunostaining, or validated single-cell result was found. Recent atlases establish the basal Gnao1/V2R population but not this receptor’s precise distribution in the retrieved evidence (devakinandan2024singlecelltranscriptomicsof pages 1-2, devakinandan2024singlecelltranscriptomicsof pages 15-17). |
| Subcellular localization | Expected to function as a plasma-membrane receptor at sensory dendritic microvilli. | V2R-family inference | Direct membrane or microvillar localization of Vmn2r73 protein has not been demonstrated; downstream TRPC2 and ANO1 are documented as microvillar-membrane enriched (mohrhardt2018signaldetectionand pages 10-11). |
| G-protein and transduction | Likely operates in the basal Gαo/Gnao1-associated pathway involving PLC-dependent phosphoinositide turnover, DAG and IP3 signaling, TRPC2-associated cation influx, depolarization, calcium elevation, and chloride-channel amplification. | V2R-family inference | Physical coupling of Vmn2r73 to Gαo or PLC has not been tested. TRPC2 is important but is not necessarily the sole transduction channel (mohrhardt2018signaldetectionand pages 6-7, mohrhardt2018signaldetectionand pages 8-9). |
| Receptor co-expression | V2R neurons commonly express one family-A, B, or D receptor together with a family-C V2R and, in defined subsets, H2-Mv molecules. Vmn2r73 may participate in this combinatorial organization. | V2R-family inference | The specific family-C partner, H2-Mv association, and co-expression pattern of Vmn2r73 were not identified (devakinandan2024singlecelltranscriptomicsof pages 17-19, devakinandan2024singlecelltranscriptomicsof pages 15-17). |
| Accessory olfactory bulb projection | If expressed in canonical basal V2R neurons, its neurons should project toward the caudal or posterior accessory olfactory bulb. | V2R-family inference | No Vmn2r73-specific axonal tracing was found. Receptor-defined studies are sparse, and studied populations can target approximately 4–30 glomeruli (hills2024molecularcellularand pages 17-19, mohrhardt2018signaldetectionand pages 11-11). |
| Biological role | Plausibly contributes to accessory-olfactory detection of social, reproductive, or interspecies chemical cues and to downstream innate neuroendocrine or behavioral responses. | V2R-family inference | No behavioral cue, circuit, sex-specific function, or physiological response has been attributed directly to Vmn2r73 (hills2024molecularcellularand pages 1-2, stempel2017comparativeanalysesof pages 21-24). |
| Knockout or phenotype | No Vmn2r73-specific knockout, perturbation, or phenotype was found. | Unknown | Phenotypes involving Gαo, TRPC2, guidance genes, or other V2Rs cannot be treated as Vmn2r73 phenotypes (hills2024molecularcellularand pages 17-19, mohrhardt2018signaldetectionand pages 8-8, mohrhardt2018signaldetectionand pages 8-9). |
| Current applications | No validated diagnostic, therapeutic, agricultural, or biotechnology application is specific to Vmn2r73. Its present value is primarily as a candidate for receptor-choice, circuit-mapping, comparative-evolution, and ligand-deorphanization research. | Unknown for direct applications; research-use inference | These proposed research uses are opportunities rather than demonstrated implementations. Recent single-cell atlases and searchable VNO resources can help prioritize cells and receptor partners for future experiments (hills2024molecularcellularand pages 1-2, hills2024molecularcellularand pages 12-14, devakinandan2024singlecelltranscriptomicsof pages 17-19). |
Table: This table separates direct database annotation of mouse Vmn2r73 from broader V2R-family inference and unknown attributes. It emphasizes that no gene-specific publication, ligand, localization experiment, signaling assay, or knockout phenotype was identified.
The best-supported annotation is that Vmn2r73 is a cell-surface chemosensory receptor expected to recognize an extracellular chemical cue and convert binding into electrical activity in a vomeronasal sensory neuron. Unlike an enzyme, it is not expected to catalyze a chemical reaction; unlike a transporter, it is not expected to translocate a substrate. Its role is receptor-mediated signal initiation.
This conclusion follows principally from its V2R/class-C GPCR architecture. In class-C receptors, the large amino-terminal extracellular region provides the likely ligand-recognition site, while the seven-transmembrane region communicates activation to heterotrimeric G proteins. The supplied ANF-like ligand-binding, nine-cysteine, and calcium-sensing-receptor-related annotations reinforce this model. Literature describes the extracellular V2R module as a hydrophobic Venus-flytrap-like ligand-binding domain (mohrhardt2018signaldetectionand pages 6-7).
No cognate ligand can currently be assigned to Vmn2r73. This is the most important annotation boundary. V2R neurons can respond to peptide/protein-rich social cues, including MHC class-I-associated peptides, major urinary proteins and exocrine-gland-secreting peptides, but these cue classes cannot be transferred automatically to every V2R (stempel2017comparativeanalysesof pages 21-24, mohrhardt2018signaldetectionand pages 5-6, mohrhardt2018signaldetectionand pages 8-9).
Only a few receptor-level assignments have strong perturbational support. For example, loss of Vmn2r26/V2r1b reduces responses to MHC peptide stimuli, while Vmn2r116/V2rp5 disruption impairs ESP1 responses; reported responses to such cues may occur at low-nanomolar to high-picomolar concentrations (mohrhardt2018signaldetectionand pages 8-8). These examples establish what some V2Rs can detect, not what Vmn2r73 detects.
Experts continue to regard V2R deorphanization as difficult because recombinant receptor expression has often failed, receptor co-expression is complex, and the natural stimulus space remains incompletely sampled. A simple one-receptor/one-ligand model is therefore unlikely to capture the system fully (mohrhardt2018signaldetectionand pages 6-7, mohrhardt2018signaldetectionand pages 5-6, mohrhardt2018signaldetectionand pages 8-8).
V2R-family expression is concentrated in basal vomeronasal sensory neurons (VSNs) in the sensory neuroepithelium of the vomeronasal organ. These neurons characteristically express Gnao1/Gαo, whereas apical V1R neurons are associated predominantly with Gnai2/Gαi2 (devakinandan2024singlecelltranscriptomicsof pages 1-2, stempel2017comparativeanalysesof pages 21-24, mohrhardt2018signaldetectionand pages 8-9, devakinandan2024singlecelltranscriptomicsof pages 15-17).
It is therefore reasonable to predict that Vmn2r73 is expressed in a sparse receptor-defined subset of basal VSNs. Nevertheless, no Vmn2r73-specific in situ hybridization, validated antibody staining, or spatial single-cell result was found; this location remains family-based inference.
As a seven-transmembrane sensory GPCR, the mature receptor is expected to function in the plasma membrane of the sensory dendritic ending, probably at or near microvilli exposed to VNO luminal stimuli. Direct localization of Vmn2r73 protein has not been demonstrated. Downstream TRPC2 and ANO1 proteins are enriched in the microvillar plasma membrane, supporting microvilli as the specialized transduction compartment (mohrhardt2018signaldetectionand pages 10-11).
Recent work also indicates that V2R/Gnao1 neurons possess an unusually specialized endoplasmic-reticulum environment. A December 2024 single-cell and ultrastructural study found higher expression of ER-associated genes and increased smooth/cubic ER in Gnao1 neurons compared with Gnai2 neurons, plausibly reflecting the folding and trafficking burden imposed by combinatorial V2R and H2-Mv expression (devakinandan2024singlecelltranscriptomicsof pages 1-2, devakinandan2024singlecelltranscriptomicsof pages 17-19). This is a population-level result and does not prove that Vmn2r73 itself requires a particular chaperone.
The canonical family-level pathway is:
extracellular cue → V2R activation → Gαo-associated GPCR signaling → phospholipase-C-dependent phosphoinositide turnover → IP3 and DAG production → TRPC2-associated cation influx → membrane depolarization and intracellular Ca²⁺ elevation → ANO1/TMEM16A-associated amplification → action-potential output.
The PLC/DAG/TRPC2 framework is supported by physiological and genetic evidence across vomeronasal neurons. TRPC2 is important but not necessarily the only transduction channel, because residual natural-stimulus responses can remain after Trpc2 loss (mohrhardt2018signaldetectionand pages 6-7, mohrhardt2018signaldetectionand pages 8-9). Selective Gαo deletion strongly compromises basal-neuron responses to MHC peptides, MUPs, ESP1 and other relevant cues, establishing Gαo as a critical component of basal chemosensitivity (mohrhardt2018signaldetectionand pages 8-9).
For Vmn2r73 specifically, physical interaction with Gαo, activation of PLC, second-messenger generation and channel opening have not been tested. The pathway should therefore be recorded as “inferred from V2R-family membership,” not as experimentally demonstrated.
Mouse V2R neurons do not obey a universally strict one-receptor-per-neuron rule. Basal neurons commonly express one family-A/B/D receptor together with a broadly expressed family-C receptor and, in certain subclasses, nonclassical MHC H2-Mv molecules (devakinandan2024singlecelltranscriptomicsof pages 1-2, devakinandan2024singlecelltranscriptomicsof pages 17-19, devakinandan2024singlecelltranscriptomicsof pages 15-17).
The family-C group contains seven highly homologous receptors with greater than 80% sequence identity. At least one family-C receptor occurs in most Gαo-positive basal VSNs, while more than 100 Vmn2r genes belong to family A and four to family D (mohrhardt2018signaldetectionand pages 8-8). Recent single-cell work found that V2R cells average more than one detected receptor and that co-expression is especially prevalent in immature neurons and young animals, indicating a genuine developmental program rather than merely technical contamination (hills2024molecularcellularand pages 12-14).
No retrieved evidence identifies Vmn2r73’s subfamily, family-C partner, H2-Mv association, transcription-factor signature, or co-expressed receptor set. These are high-priority annotation gaps.
Basal V2R neurons project through the vomeronasal nerve to the caudal/posterior accessory olfactory bulb (AOB), spatially separated from the predominantly rostral target of V1R neurons (stempel2017comparativeanalysesof pages 21-24, mohrhardt2018signaldetectionand pages 11-11). Robo2 is broadly associated with V2R populations, and Robo2 loss shifts their axons toward rostral AOB territories; Kirrel and protocadherin programs further help organize receptor-defined glomeruli (hills2024molecularcellularand pages 17-19, hills2024molecularcellularand pages 14-15, hills2024molecularcellularand pages 15-17).
Tracing of the few receptor-defined populations studied has yielded target ensembles of approximately 4–30 glomeruli, but experts caution against generalizing this range because relatively few V2Rs have been traced and AOB glomerular boundaries are difficult to resolve (mohrhardt2018signaldetectionand pages 11-11). Thus, a posterior-AOB projection is plausible for Vmn2r73 neurons, but its exact glomerular targets remain unknown.
At the systems level, VNO–AOB signaling conveys inter- and intraspecies chemical information into amygdalar and hypothalamic circuits that regulate innate social, reproductive, defensive and neuroendocrine responses (hills2024molecularcellularand pages 1-2, stempel2017comparativeanalysesof pages 21-24). No particular cue or behavior—mate recognition, aggression, predator avoidance, parental behavior or reproductive endocrine response—has been demonstrated for Vmn2r73.
The most relevant recent advance was not deorphanization of Vmn2r73 but a major improvement in the cellular framework in which it can be studied.
These results revise the older simplified picture of singular receptor expression. They suggest that functional deorphanization of Vmn2r73 may require reconstructing its natural receptor partners, H2-Mv context and cell-specific trafficking machinery rather than expressing Vmn2r73 alone.
No diagnostic, therapeutic, agricultural or commercial application specific to Vmn2r73 was found. Its present value is as a research target for understanding mammalian chemical communication, receptor-choice mechanisms, GPCR trafficking, sensory-circuit assembly and rapidly evolving gene families.
The immediate practical implementations are experimental: use the 2024 single-cell resources to identify Vmn2r73-positive cells and co-receptors; validate expression by RNAscope or targeted in situ hybridization; map protein localization with a sequence-specific antibody or epitope-tagged knock-in; identify responsive cues by calcium imaging/electrophysiology followed by receptor-directed perturbation; and trace axons from a Vmn2r73 reporter allele. Heterologous deorphanization should reproduce likely family-C/H2-Mv and ER-trafficking partners because isolated V2R expression is technically unreliable (devakinandan2024singlecelltranscriptomicsof pages 17-19, mohrhardt2018signaldetectionand pages 6-7, devakinandan2024singlecelltranscriptomicsof pages 15-17).
Conservative annotation: “Predicted vomeronasal type-2 chemosensory receptor; class-C seven-transmembrane GPCR likely expressed in basal Gαo-positive vomeronasal sensory neurons and involved in PLC/TRPC2-associated accessory-olfactory signal transduction.”
Do not currently annotate: a specific pheromone or kairomone ligand; binding affinity; direct Gαo coupling; exact microvillar localization; H2-Mv or family-C partner; AOB glomerulus; behavioral function; or knockout phenotype.
Overall evidence is high for identity and predicted receptor architecture, moderate for cellular pathway and localization inferred from V2R-family biology, and absent or insufficient for a Vmn2r73-specific ligand, signaling mechanism, circuit or organismal function.
References
(mohrhardt2018signaldetectionand pages 6-7): Julia Mohrhardt, Maximilian Nagel, David Fleck, Yoram Ben-Shaul, and Marc Spehr. Signal detection and coding in the accessory olfactory system. Chemical Senses, 43:667-695, Sep 2018. URL: https://doi.org/10.1093/chemse/bjy061, doi:10.1093/chemse/bjy061. This article has 134 citations and is from a peer-reviewed journal.
(mohrhardt2018signaldetectionand pages 5-6): Julia Mohrhardt, Maximilian Nagel, David Fleck, Yoram Ben-Shaul, and Marc Spehr. Signal detection and coding in the accessory olfactory system. Chemical Senses, 43:667-695, Sep 2018. URL: https://doi.org/10.1093/chemse/bjy061, doi:10.1093/chemse/bjy061. This article has 134 citations and is from a peer-reviewed journal.
(stempel2017comparativeanalysesof pages 21-24): Hendrik Stempel. Comparative analyses of murine and human formyl peptide receptor 3. ArXiv, Jun 2017. URL: https://doi.org/10.22028/d291-22290, doi:10.22028/d291-22290. This article has 0 citations.
(mohrhardt2018signaldetectionand pages 8-8): Julia Mohrhardt, Maximilian Nagel, David Fleck, Yoram Ben-Shaul, and Marc Spehr. Signal detection and coding in the accessory olfactory system. Chemical Senses, 43:667-695, Sep 2018. URL: https://doi.org/10.1093/chemse/bjy061, doi:10.1093/chemse/bjy061. This article has 134 citations and is from a peer-reviewed journal.
(devakinandan2024singlecelltranscriptomicsof pages 1-2): GVS Devakinandan, Mark Terasaki, and Adish Dani. Single-cell transcriptomics of vomeronasal neuroepithelium reveals a differential endoplasmic reticulum environment amongst neuronal subtypes. Dec 2024. URL: https://doi.org/10.7554/elife.98250.3, doi:10.7554/elife.98250.3. This article has 6 citations and is from a domain leading peer-reviewed journal.
(devakinandan2024singlecelltranscriptomicsof pages 15-17): GVS Devakinandan, Mark Terasaki, and Adish Dani. Single-cell transcriptomics of vomeronasal neuroepithelium reveals a differential endoplasmic reticulum environment amongst neuronal subtypes. Dec 2024. URL: https://doi.org/10.7554/elife.98250.3, doi:10.7554/elife.98250.3. This article has 6 citations and is from a domain leading peer-reviewed journal.
(mohrhardt2018signaldetectionand pages 10-11): Julia Mohrhardt, Maximilian Nagel, David Fleck, Yoram Ben-Shaul, and Marc Spehr. Signal detection and coding in the accessory olfactory system. Chemical Senses, 43:667-695, Sep 2018. URL: https://doi.org/10.1093/chemse/bjy061, doi:10.1093/chemse/bjy061. This article has 134 citations and is from a peer-reviewed journal.
(mohrhardt2018signaldetectionand pages 8-9): Julia Mohrhardt, Maximilian Nagel, David Fleck, Yoram Ben-Shaul, and Marc Spehr. Signal detection and coding in the accessory olfactory system. Chemical Senses, 43:667-695, Sep 2018. URL: https://doi.org/10.1093/chemse/bjy061, doi:10.1093/chemse/bjy061. This article has 134 citations and is from a peer-reviewed journal.
(devakinandan2024singlecelltranscriptomicsof pages 17-19): GVS Devakinandan, Mark Terasaki, and Adish Dani. Single-cell transcriptomics of vomeronasal neuroepithelium reveals a differential endoplasmic reticulum environment amongst neuronal subtypes. Dec 2024. URL: https://doi.org/10.7554/elife.98250.3, doi:10.7554/elife.98250.3. This article has 6 citations and is from a domain leading peer-reviewed journal.
(hills2024molecularcellularand pages 17-19): Max Hills, Limei Ma, Ai Fang, Thelma Chiremba, Seth Malloy, Allison Scott, Anoja Perera, and C. Ron Yu. Molecular, cellular, and developmental organization of the mouse vomeronasal organ at single cell resolution. eLife, Dec 2024. URL: https://doi.org/10.7554/elife.97356, doi:10.7554/elife.97356. This article has 16 citations and is from a domain leading peer-reviewed journal.
(mohrhardt2018signaldetectionand pages 11-11): Julia Mohrhardt, Maximilian Nagel, David Fleck, Yoram Ben-Shaul, and Marc Spehr. Signal detection and coding in the accessory olfactory system. Chemical Senses, 43:667-695, Sep 2018. URL: https://doi.org/10.1093/chemse/bjy061, doi:10.1093/chemse/bjy061. This article has 134 citations and is from a peer-reviewed journal.
(hills2024molecularcellularand pages 1-2): Max Hills, Limei Ma, Ai Fang, Thelma Chiremba, Seth Malloy, Allison Scott, Anoja Perera, and C. Ron Yu. Molecular, cellular, and developmental organization of the mouse vomeronasal organ at single cell resolution. eLife, Dec 2024. URL: https://doi.org/10.7554/elife.97356, doi:10.7554/elife.97356. This article has 16 citations and is from a domain leading peer-reviewed journal.
(hills2024molecularcellularand pages 12-14): Max Hills, Limei Ma, Ai Fang, Thelma Chiremba, Seth Malloy, Allison Scott, Anoja Perera, and C. Ron Yu. Molecular, cellular, and developmental organization of the mouse vomeronasal organ at single cell resolution. eLife, Dec 2024. URL: https://doi.org/10.7554/elife.97356, doi:10.7554/elife.97356. This article has 16 citations and is from a domain leading peer-reviewed journal.
(hills2024molecularcellularand pages 14-15): Max Hills, Limei Ma, Ai Fang, Thelma Chiremba, Seth Malloy, Allison Scott, Anoja Perera, and C. Ron Yu. Molecular, cellular, and developmental organization of the mouse vomeronasal organ at single cell resolution. eLife, Dec 2024. URL: https://doi.org/10.7554/elife.97356, doi:10.7554/elife.97356. This article has 16 citations and is from a domain leading peer-reviewed journal.
(hills2024molecularcellularand pages 15-17): Max Hills, Limei Ma, Ai Fang, Thelma Chiremba, Seth Malloy, Allison Scott, Anoja Perera, and C. Ron Yu. Molecular, cellular, and developmental organization of the mouse vomeronasal organ at single cell resolution. eLife, Dec 2024. URL: https://doi.org/10.7554/elife.97356, doi:10.7554/elife.97356. This article has 16 citations and is from a domain leading peer-reviewed journal.