Determination of the animal-vegital and left-right axes using a simple chordate, Oikopleura dioica.

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K06256
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 44020:Developmental biology-related
• Research Institution: Kagoshima University (2021); Osaka University (2018-2020)
• Principal Investigator: Onuma Takeshi 鹿児島大学, 理工学域理学系, 准教授 (30632103)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: オタマボヤ / 脊索動物 / 動植軸 / 左右軸 / Nodal / Bmp / 母性mRNA / 進化

Outline of Final Research Achievements

An important question in developmental biology is how embryonic axes (animal-vegital (AV)-axis, the axis perpendicular to the AV-axis, and the left-right (LR)-axis) are formed during embryogenesis. In this study, we investigated the (1) AV-axis and (2) LR-axis by taking advantages of a small chordate, Oikopleura dioica, as an experimental animal.
(1) AV-axis. Maternal mRNAs localizing in the posterior part of the vegital hemisphere were found. These maternal mRNAs are concentrated to the vestigial pole region of unfertilized eggs. Furthermore, we found that the vegital mRNA localization was established during oogenesis in the ovary.
(2) LR-axis. In O. dioica, the nerve cord is located on the left, not dorsal, side of the tadpole larvae. We found that this animal lacks Nodal, but utilizes right-sided Bmp expression for LR patterning. O. dioica can be serve as an example that the dorsal-ventral axis formation via Bmp expression can induce a 90°rotation for LR-patterning.

Free Research Field

発生生物学

Academic Significance and Societal Importance of the Research Achievements

脊索動物のオタマボヤを活かして、発生学の命題の1つである胚軸の決定機構の理解に貢献した。たとえば (1) 動植軸はすべての動物で未受精卵から存在する。12時間という卵形成の短さを活用することで、卵母細胞の対称性が破られるしくみ、すなわち母性mRNAがいつ、どのように動植軸にそって局在するのかを明らかにした。(2) 左右軸についても、110年前にH.C. Delsman博士が記載した現象を掘り起こし、「Bmpによる背腹形成を転用した左右形成」という概念を提唱した。
このように、独自に開発した「単純な体の脊索動物」を活用して、発生学の新しい研究領域を開拓した。