Expression of type1 vomeronasal receptors in the olfactory organ of lungfish

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K06399
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 42020:Veterinary medical science-related
• Research Institution: Iwate University (2021-2022); Iwate Medical University (2020)
• Principal Investigator: Nakamuta Shoko 岩手大学, 農学部, 特任研究員 (70724532)
• Co-Investigator(Kenkyū-buntansha): 中牟田 信明 岩手大学, 農学部, 准教授 (00305822) ; 二階堂 雅人 東京工業大学, 生命理工学院, 准教授 (70432010)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 1型鋤鼻受容体 / ハイギョ / 嗅上皮 / 鋤鼻器 / in situ hybridization

Outline of Final Research Achievements

Most tetrapods possess two distinct olfactory organs, the olfactory epithelium (OE) and the vomeronasal organ (VNO). Lungfish, the closest fish to amphibians, has the lamellar OE and a primitive VNO (the recess epithelium, RecE). We identified the V1R genes in five of the six extant species of lungfish (four African and one South American lungfish) by RNA-seq. Most V1Rs identified in these lungfish were classified as the tetrapod-type V1Rs initially found in tetrapods and distinct from fish-type V1Rs. In situ hybridization analysis indicated that lungfish V1Rs were expressed mainly in the lamellar OE and rarely in the RecE. In addition, the juveniles showed a higher density of V1R-expressing cells in the lamellar OE compared with the adults.

Free Research Field

獣医解剖学

Academic Significance and Societal Importance of the Research Achievements

魚はVNOを持たず、OEにすべての嗅覚受容体が発現している。進化の過程で、匂い受容体と鋤鼻受容体の発現部位が分かれて四足動物のOEとVNOが生じたと考えられているが、その詳細な過程は不明であった。本研究成果はハイギョと両生類の共通祖先の嗅覚器に鋤鼻受容体（V1R/V2R）を発現する場として原始的VNOが誕生したが、進化の過程でV1Rの発現が失われ、両生類のVNO（V2Rだけを発現）が生じたことを示唆する。