Syed Adnan S, Sansone Alfredo, Hassenklöver Thomas, Manzini Ivan, Korsching Sigrun I
Institute of Genetics, Biocenter, University of Cologne, Zülpicher Strasse 47a, 50674, Cologne, Germany.
Institute of Neurophysiology and Cellular Biophysics, University of Göttingen, Humboldtallee 23, 37073, Göttingen, Germany.
Cell Mol Life Sci. 2017 May;74(9):1711-1719. doi: 10.1007/s00018-016-2437-1. Epub 2016 Dec 18.
All olfactory receptors identified in teleost fish are expressed in a single sensory surface, whereas mammalian olfactory receptor gene families segregate into different olfactory organs, chief among them the main olfactory epithelium expressing ORs and TAARs, and the vomeronasal organ expressing V1Rs and V2Rs. A transitional stage is embodied by amphibians, with their vomeronasal organ expressing more 'modern', later diverging V2Rs, whereas more 'ancient', earlier diverging V2Rs are expressed in the main olfactory epithelium. During metamorphosis, the main olfactory epithelium of Xenopus tadpoles transforms into an air-filled cavity (principal cavity, air nose), whereas a newly formed cavity (middle cavity) takes over the function of a water nose. We report here that larval expression of ancient V2Rs is gradually lost from the main olfactory epithelium as it transforms into the air nose. Concomitantly, ancient v2r gene expression begins to appear in the basal layers of the newly forming water nose. We observe the same transition for responses to amino acid odorants, consistent with the hypothesis that amino acid responses may be mediated by V2R receptors.
硬骨鱼中鉴定出的所有嗅觉受体都在单一感觉表面表达，而哺乳动物的嗅觉受体基因家族则分隔在不同的嗅觉器官中，其中主要的是表达嗅觉受体（ORs）和痕量胺相关受体（TAARs）的主嗅觉上皮，以及表达V1Rs和V2Rs的犁鼻器。两栖动物体现了一个过渡阶段，它们的犁鼻器表达更多“现代”、分化较晚的V2Rs，而更多“古老”、分化较早的V2Rs则在主嗅觉上皮中表达。在变态过程中，非洲爪蟾蝌蚪的主嗅觉上皮转变为一个充满空气的腔（主腔，气鼻），而一个新形成的腔（中腔）接管了水鼻的功能。我们在此报告，随着主嗅觉上皮转变为气鼻，古老V2Rs的幼虫表达在其中逐渐消失。与此同时，古老的v2r基因表达开始出现在新形成的水鼻的基底层。我们观察到对氨基酸气味剂的反应也有相同的转变，这与氨基酸反应可能由V2R受体介导的假设一致。
