How we humans lost a tail?: Investigation of tail morphogenetic process in short-tailed amniotes during embryonic development

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K15008
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 48010:Anatomy-related
• Research Institution: Osaka City University
• Principal Investigator: Tojima Sayaka 大阪市立大学, 大学院医学研究科, 助教 (10792830)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: しっぽ / 発生 / 退縮

Outline of Final Research Achievements

Tail length is considered as an important feature indicating adaptation and evolution. However, the mechanisms by which it is determined during development has not been clarified. Thus, I performed 3 different research projects for clarification of the tail reduction mechanism during embryonic development. From the first project using chicken embryos, I found that apoptosis in the caudal neural tube is possibly important for tail reduction. Additionally, the findings from the second project showed that tail reduction was broadly observed in short-tailed amniote species. This suggested that this developmental mechanism might be highly preserved in multiple taxa. These findings were helpful not only to understand developmental process but also a congenital anomaly known as “human tail”. This anomaly has been believed to be caused by aberration of tail reduction since the 1900’s. However, my study regarding tail reduction has revealed that the previous hypothesis is not correct.

Free Research Field

解剖学、発生生物学

Academic Significance and Societal Importance of the Research Achievements

本研究は、多様な系統群で尾部形態形成を観察することで、胚発生過程において生じる尾部退縮が尾部形態形成に重要であることを示した点で新規的である。また、短尾という極端な形質をもつ有羊膜類において尾部退縮という発生現象が幅広く保存されている可能性が高いことは、進化を考える上で興味深い知見を提供したと言える。さらに、生物学的研究意義の高さに留まらず、基礎的知見をヒト先天異常の要因解明という臨床応用に昇華させた点でも大きな意義をもつ。