Size-dependent temporal decoupling of morphogenesis and transcriptional programs in pseudo-embryos [scRNA-seq]

Understanding the interplay between cell fate specification and morphogenetic changes remains a central challenge in developmental biology. Gastruloids, self-organizing pseudo-embryos that mimic post-implantation mammalian development, provide a powerful platform to address this question. Here, we show that physical parameters, particularly system size, critically influence the timing and outcomes of morphogenetic processes. Larger gastruloids exhibit delayed symmetry breaking, increased multipolarity, and prolonged axial elongation, with morphogenesis driven by system size. Despite these variations, transcriptional programs and cell fate composition remain remarkably stable across a broad size range. Notably, extreme sizes show distinct transcriptional modules and clear shifts in gene expression patterns. Intriguingly, size perturbation experiments rescued the morphogenetic and pattern phenotypes observed in extreme sizes, demonstrating the remarkable adaptability of gastruloids to their effective system size. These findings establish gastruloids as versatile models for studying spatiotemporal dynamics in mammalian embryogenesis and reveal how physical constraints decouple transcriptional from morphogenetic programs. scRNA-seq on gastruloids grown from various initial cell seeding number

解析细胞命运特化与形态发生变化之间的相互作用，始终是发育生物学领域的核心难题。类原肠胚（Gastruloids）是一类可自我组织的类胚胎结构，能够模拟哺乳动物植入后发育过程，为解答该问题提供了强有力的研究平台。本研究发现，物理参数尤其是系统尺寸，会显著影响形态发生过程的时序与最终结果。较大尺寸的类原肠胚会表现出对称性打破延迟、多极性增强以及轴向伸长过程延长的特征，其形态发生过程由系统尺寸主导。尽管存在上述差异，在较宽的尺寸范围内，类原肠胚的转录程序与细胞命运组成仍保持显著稳定。值得注意的是，极端尺寸的类原肠胚会呈现出独特的转录模块，以及基因表达模式的显著改变。有趣的是，通过尺寸扰动实验，可挽救极端尺寸类原肠胚所出现的形态发生与模式表型，这证明类原肠胚能够根据有效系统尺寸展现出出色的适应性。本研究结果确立了类原肠胚作为研究哺乳动物胚胎发生时空动态的通用模型，并揭示了物理约束如何使转录程序与形态发生程序解耦。针对由不同初始细胞接种量培养得到的类原肠胚的单细胞RNA测序（scRNA-seq）