Transcriptional instability prevents dispersion of functional vomeronasal receptor genes [scRNA-seq]
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ABSTRACT: Rodents perceive pheromones via vomeronasal receptors encoded by the Vr and Fpr gene superfamilies. The evolution of these latter is exceptionally dynamic. We report here that high numbers of V1r pseudogenes are scattered in mammalian genomes, contrasting with the clustered organization of functional V1r and Fpr genes. We also found that V1r pseudogenes are more likely to be expressed when located in a functional V1r gene cluster than when isolated. To explore the potential regulatory role played by the association of functional vomeronasal receptor genes with their clusters, we dissociated the mouse Fpr-rs3 from its native cluster via transgenesis. Singular and specific transgenic Fpr-rs3 transcription was observed in young vomeronasal neurons, but was only transient. Our data point to the existence of transcription stabilizing elements not coupled to vomeronasal gene units but rather associated with vomeronasal gene clusters, and thus explain the evolutionary conserved clustered organization of functional vomeronasal genes.
Project description:Rodents perceive pheromones via vomeronasal receptors encoded by the Vr and Fpr gene superfamilies. The evolution of these latter is exceptionally dynamic. We report here that high numbers of V1r pseudogenes are scattered in mammalian genomes, contrasting with the clustered organization of functional V1r and Fpr genes. We also found that V1r pseudogenes are more likely to be expressed when located in a functional V1r gene cluster than when isolated. To explore the potential regulatory role played by the association of functional vomeronasal receptor genes with their clusters, we dissociated the mouse Fpr-rs3 from its native cluster via transgenesis. Singular and specific transgenic Fpr-rs3 transcription was observed in young vomeronasal neurons, but was only transient. Our data point to the existence of transcription stabilizing elements not coupled to vomeronasal gene units but rather associated with vomeronasal gene clusters, and thus explain the evolutionary conserved clustered organization of functional vomeronasal genes.
Project description:Rodents perceive pheromones via vomeronasal receptors encoded by the Vr and Fpr gene superfamilies. The evolution of these latter is exceptionally dynamic. We report here that high numbers of V1r pseudogenes are scattered in mammalian genomes, contrasting with the clustered organization of functional V1r and Fpr genes. We also found that V1r pseudogenes are more likely to be expressed when located in a functional V1r gene cluster than when isolated. To explore the potential regulatory role played by the association of functional vomeronasal receptor genes with their clusters, we dissociated the mouse Fpr-rs3 from its native cluster via transgenesis. Singular and specific transgenic Fpr-rs3 transcription was observed in young vomeronasal neurons, but was only transient. Our data point to the existence of transcription stabilizing elements not coupled to vomeronasal gene units but rather associated with vomeronasal gene clusters, and thus explain the evolutionary conserved clustered organization of functional vomeronasal genes.
Project description:The vomeronasal organ of mice consists of two major types of vomeronasal sensory neurons (VSNs) expressing either receptors of the V1R or V2R family. V1R and V2R VSNs form from a common pool of progenitors but have distinct differentiation programs. We analyzed single cell RNA sequencing data of adult VNO and identified differential expression of Notch1 receptor and Dll4 ligand among the neuronal precursors at the VSN dichotomy. We further demonstrated that Notch signaling is required for effective differentiation of V2R+ basal VSNs.
Project description:The vomeronasal organ (VNO) of mice contains two main types of vomeronasal sensory neurons (VSNs)- Apical and Basal. Apical VSNs express vomeronasal receptors (VRs) of the V1R family and project to the anterior accessory olfactory bulb (AOB) and VSNs in the basal portions of the epithelium express receptors of the V2R family and project to the posterior portion of the AOB. In the vomeronasal epithelium of mice we found active BMP signaling. By generating Smad4 conditional mutants we disrupted canonical TGF-b/BMP signaling in either maturing basal VSNs or in mature apical and basal VSNs.
Project description:We have generated single cell transcriptomic atlases of vomeronasal organs (VNO) from juvenile and adult mice. Combined with spatial molecular imaging, we uncover a distinct, previously unidentified class of cells that express the vomeronasal receptors and a population of canonical olfactory sensory neurons in the VNO. High resolution trajectory and cluster analyses reveal the lineage relationship, spatial distribution of cell types, and a putative cascade of molecular events that specify the V1r, V2r, and OR lineages from a common stem cell population. The expression of vomeronasal and olfactory receptors follow power law distributions, but there are high variabilities in average expression levels between individual receptor and cell types. Substantial co-expression is found between receptors across clades, from different classes, and between olfactory and vomeronasal receptors, with nearly half from pairs located on the same chromosome. Interestingly, the expression of V2r, but not V1r, genes is associated with various transcription factors, suggesting distinct mechanisms of receptor choice associated with the two cell types. We identify association between transcription factors, surface axon guidance molecules, and individual VRs, thereby uncovering a molecular code that guides the specification of the vomeronasal circuitry. Our study provides a wealth of data on the development and organization of the accessory olfactory system at both cellular and molecular levels to enable a deeper understanding of vomeronasal system function.
Project description:Understanding the molecular mechanisms defining and maintaining the identity of a specific neuronal cell type is a central goal in neuroscience. The vomeronasal organ (VNO) of mice contains hundreds of distinct vomeronasal sensory neurons (VSNs). The VSNs are classified into two major cell types that are segregated in apical and basal regions of the VNO, express vomeronasal receptors of different superfamilies, and send axons to different portions of the accessory olfactory bulb. How apical or basal identity of VSNs is established and maintained is largely unknown. Here we attempt to assess the role of a single transcription factor, AP-2ε, in the VNO of mice. We used microarrays to examine global effect of AP-2ε loss-of-function on gene expression in the vomeronasal organ.