Origin and evolution of sensory centers in the vertebrate Brain

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K06892
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 46020:Anatomy and histopathology of nervous system-related
• Research Institution: Ehime University
• Principal Investigator: Murakami Yasunori 愛媛大学, 理工学研究科(理学系), 教授 (50342861)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 脊椎動物 / 脳 / 進化 / 発生

Outline of Final Research Achievements

The purpose of this study was to investigate the evolutionary transitions leading to the development of diverse higher centers using amniotes, ray-finned fishes, cartilaginous fishes, and cyclostomes. It was previously believed that cyclostomes only possess an undifferentiated cerebellum. However, in the brains of cyclostomes, genes involved in the development of the cerebellum are expressed, and their location corresponds to where the cerebellum is formed in other vertebrates. This suggests the possibility that the developmental mechanism of the cerebellum was already established at the stage of the common ancestor of vertebrates. Furthermore, we have confirmed significant differences in the trigeminal nerve, which controls the jaw, between cyclostomes and cartilaginous fishes. Based on these findings, we have proposed a model regarding the process that occurred during the divergence of gnathostomes (jawed vertebrates) and cyclostomes.

Free Research Field

進化形態学

Academic Significance and Societal Importance of the Research Achievements

脊椎動物の脳は、進化の初期の段階で多くの要素が獲得されたと考えられているが、その背景にある分子機構については不明な点が多い。本研究から、小脳の発生機構は脊椎動物の共通祖先の段階ですでに出来上がっていた可能性が示唆された。つまり円口類は小脳発生機構を持っているが、進化の過程では何らかの要因によりそれが起動することがなかったと考えられる。このような事例があったことが示されたことで、進化発生学の分野に新たに考察する価値のある進化シナリオを提示することができた。さらに、新規な形態が獲得される際に神経系はどのように変わるかという問題について、顎を支配する神経を例として、新規な考えを提供することができた。