動物の形づくりに潜む力学的リスク～ハエが進化させた、「組織同士の衝突」を防ぐ二つの仕組み～

2025-09-18

2025-09-17 理化学研究所

理化学研究所らの国際共同研究チームは、ショウジョウバエの初期胚で頭部と胴部の境界に一時的に現れる「セファリック・ファロウ(CF)」の役割を解明した。CFは体や器官にならない構造だが、発生に伴う境界部の力学的ストレスを胚内部に逃し、上皮組織同士の衝突を防ぐ働きを持つことが判明した。さらに、CFを持たないユスリカなどの昆虫では細胞分裂方向を制御する別の仕組みでストレスを緩和していることも明らかにした。本研究は、多数の細胞が狭い空間で動く動物発生において、正常な形態形成を守る進化的戦略を示したもの。成果はNature誌に掲載された。

CFを形成するショウジョウバエ胚(左)と、CFを形成しないユスリカ胚(右)

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胚盤葉形成における組織衝突を回避する分岐進化戦略 Divergent evolutionary strategies pre-empt tissue collision in gastrulation

Bipasha Dey,Verena Kaul,Girish Kale,Maily Scorcelletti,Michiko Takeda,Yu-Chiun Wang & Steffen Lemke
Nature Published:03 September 2025
DOI:https://doi.org/10.1038/s41586-025-09447-4

Abstract

Metazoan development proceeds through a series of morphogenetic events that sculpt body plans and organ structures^1,2. In the early embryo, these processes occur concurrently such that forces generated in neighbouring tissues can impose mechanical stresses on each other^3,4,5, potentially disrupting development and consequently decreasing fitness. How organisms evolved mechanisms to mitigate inter-tissue mechanical conflicts remains unclear. Here, we combined phylogenetic survey, quantitative live imaging and functional mechanical perturbation to investigate mechanical stress management during gastrulation across the insect order of flies (Diptera). We identify two distinct cellular mechanisms that prevent tissue collision between the expanding head and trunk. In Cyclorrhapha, a monophyletic subgroup including Drosophila melanogaster, active out-of-plane deformation of a transient epithelial fold, called the cephalic furrow, acts as a mechanical sink to pre-empt head–trunk collision. Genetic and optogenetic ablation of the cephalic furrow leads to accumulation of compressive stress, tissue buckling at the head–trunk boundary and late-stage embryonic defects in the head and nervous system. By contrast, the non-cyclorrhaphan Chironomus riparius lacks cephalic furrow formation and instead undergoes widespread out-of-plane division that reduces the duration and spatial extent of head expansion. Re-orienting head mitosis from in-plane to out-of-plane in Drosophila partially suppresses tissue buckling, showing that it can function as an alternative mechanical sink. Our data suggest that mechanisms of mechanical stress management emerge and diverge in response to inter-tissue conflicts during early embryonic development.