Mesoderm arises at gastrulation and contributes to both the mouse embryo proper and its extra-embryonic membranes. Two-photon live imaging of embryos bearing a keratin reporter allowed recording filament nucleation and elongation in the extra-embryonic region. Upon separation of amniotic and exocoelomic cavities, keratin 8 formed apical cables co-aligned across multiple cells in the amnion, allantois, and blood islands. An influence of substrate rigidity and composition on cell behavior and keratin content was observed in mesoderm explants. Embryos lacking all keratin filaments displayed a deflated extra-embryonic cavity, a narrow thick amnion, and a short allantois. Single-cell RNA sequencing of sorted mesoderm cells and micro-dissected amnion, chorion, and allantois, provided an atlas of transcriptomes with germ layer and regional information. It defined the cytoskeleton and adhesion expression profile of mesoderm-derived keratin 8-enriched cells lining the exocoelomic cavity. Those findings indicate a novel role for keratin filaments in the expansion of extra-embryonic structures and suggest mechanisms of mesoderm adaptation to the environment.

中文翻译：

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角蛋白丝介导原肠胚形成后小鼠胚胎中胚外膜的扩张。

中胚层在原肠胚形成时出现，并有助于小鼠胚胎本身及其胚外膜。带有角蛋白报告基因的胚胎的双光子实时成像允许记录胚胎外区域的细丝成核和伸长。在羊膜腔和外腔腔分离后，角蛋白 8 形成了跨羊膜、尿囊和血岛中多个细胞的顶端电缆。在中胚层外植体中观察到基质硬度和组成对细胞行为和角蛋白含量的影响。缺少所有角蛋白丝的胚胎显示出缩小的胚外腔、狭窄的厚羊膜和短小的尿囊。对分选的中胚层细胞和显微解剖的羊膜、绒毛膜和尿囊进行单细胞 RNA 测序，提供了具有胚层和区域信息的转录组图谱。它定义了外体腔内衬的中胚层来源的富含角蛋白 8 的细胞的细胞骨架和粘附表达谱。这些发现表明角蛋白丝在胚外结构扩张中的新作用，并提出了中胚层适应环境的机制。