Fluctuations of the avian digit pattern

2019 Fiscal Year Final Research Report

• Project/Area Number: 17KT0106
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 特設分野
• Research Field: Constructive Systems Biology
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Tanaka Mikiko 東京工業大学, 生命理工学院, 准教授 (40376950)
• Project Period (FY): 2017-07-18 – 2020-03-31
• Keywords: 形態進化

Outline of Final Research Achievements

Variation in digit number has occurred multiple times in the history of archosaur evolution. The five digits of dinosaur limbs were reduced to three in bird forelimbs, and were further reduced in the vestigial forelimbs of the emu. Regulation of digit number has been investigated previously by examining genes involved in anterior-posterior patterning in forelimb buds among emu, chicken and zebra finch. We found that the dynamic expression pattern of the BMP antagonist Gremlin1 (Grem1) in limb buds, which is critical for autopodial expansion, was consistent with the digital pattern of emu, chicken and zebra finch. Furthermore, in emu, variation among individuals was observed in the width of Grem1 expression in forelimb buds, as well as in the adult skeletal pattern. Our results support the view that the signalling system that regulates the dynamic expression of Grem1 in the limb bud contributes substantially to variations in avian digital patterns.

Free Research Field

進化発生生物学

Academic Significance and Societal Importance of the Research Achievements

鳥類の指パターンについては、異種間で多様な指パターンを示す原因やその進化の軌跡を探求する研究が盛んであり、エミューの指に着目した研究も含めて、近年、高い関心を得ている。本研究では、鳥類の同一種内で指パターンにばらつきが存在することを骨格パターンと遺伝子パターンの両者から示した初めての報告となった。一方、本研究の遂行により、エミューの前肢パターンには、今回見つけた遺伝子の発現パターンのゆらぎだけではできない個体差も存在していることが示唆されており、指パターンのゆらぎを生み出す新たな機構が存在する可能性の提案へとつながった。