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Dryad

Collective fate decisions and cell rearrangements underlie gastruloid symmetry breaking

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Sep 11, 2026 version files 5.67 GB

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Abstract

How cell fate decisions coordinate with tissue-scale morphogenesis remains a major challenge in developmental biology. Gastruloids, three-dimensional aggregates of pluripotent stem cells that self-organise and break symmetry via polarised Brachyury/T expres-sion, provide an ideal system to address this question. By generating gastruloids with defined initial proportions of T-expressing cells we show that fate decisions occur collectively, with cell-fate proportions influencing the transition rates. Mechanical measurements reveal differences in surface tension between T-positive and T-negative tissues, consistent with radial cell sorting. Finally, incorporating fate dynamics and mechanics into a computational model recapitulates the sequential symmetry-breaking events observed in vitro. Our findings identify a mechanochemical mechanism underlying axis formation, and demonstrate how multicellular systems can robustly self-organise without external signalling cues.