Fig. 1

Next generation RNA sequencing and quantitative PCR reveal high and unique expression of an odorant receptor (OR) gene in the mouse vomeronasal organ. (a–c) RNA sequencing expression data for selected genes represented as mean fragments per kilobase of annotated sequence per million reads (FPKM). Error bars are the standard error of the mean (SEM). The first seven OR genes have FPKM >1.0 in the vomeronasal organ (VNO) library; the remaining OR genes have been reported to be expressed in juveniles [23]. Black bars represent vomeronasal receptor (VR) genes, for comparison. Expression of Olfr692, marked in red, stands out as high in the VNO, higher in the VNO than in the main olfactory epithelium (MOE), and comparable to the expression of VR genes. (a) Adult VNO libraries (n = 6 libraries; each library was from VNOs pooled from three individuals); (b) Adult MOE libraries (n = 6 libraries; each library was from one individual); (c) Juvenile libraries (n = 3 libraries; each library was from VNOs pooled from three to four individuals). (d) Seven OR genes with mean FPKM values >1.0 in adult VNO libraries, showing no difference in expression between males and females. 'mOR name' refers to alternate mOR nomenclature [2]. Raw counts are number of reads uniquely mapped to genomic model. The right column indicates mean FPKM in the VNO. Chr, mouse genome chromosomal location. OR genes with FPKM values >1.0 are located in distinct chromosomes, suggesting that their expression in the VNO is not related to their genomic position. (e) Comparison between FPKM values for OR genes in the adult MOE (red bars) and VNO (blue bars), illustrating that Olfr692 expression is uniquely VNO-enriched. The x-axis is ordered according to expression level in the MOE. (f) Comparison between FPKM for OR (large diamonds) and VR (small diamonds) genes in the VNO. The two most abundant OR genes, Olfr124 and Olfr692, are labeled. The top part shows the number of VR genes with FPKM values lower or higher than Olfr692 (419 VR genes, including 171 pseudogenes, exhibit lower values; 114 VR genes, including five pseudogenes, exhibit higher values). The x-axis scale is different to the left and right of an interruption at FPKM = 10. (g) Real-time qPCR using TaqMan probes to validate the expression of OR genes which have mean FPKM values >1.0 in the adult VNO RNA seq libraries. The y-axis indicates relative expression level (RQ) as compared to the expression of β-actin. Gray bars indicate expression levels in whole VNO samples and red bars represent the finely dissected VNO neuroepithelium. Error bars are SEM (n = 4 animals, three technical replicates)