Search

The body plan of the mammalian embryo is shaped through the process of gastrulation, an early developmental event that transforms an isotropic group of cells into an ensemble of tissues that is ordered with reference to three orthogonal axes1. Although model organisms have provided much insight into this process, we know very little about gastrulation in humans, owing to the difficulty of obtaining embryos at such early stages of development and the ethical and technical restrictions that limit the feasibility of observing gastrulation ex vivo2. Here we show that human embryonic stem cells can be used to generate gastruloids-three-dimensional multicellular aggregates that differentiate to form derivatives of the three germ layers organized spatiotemporally, without additional extra-embryonic tissues. Human gastruloids undergo elongation along an anteroposterior axis, and we use spatial transcriptomics to show that they exhibit patterned gene expression. This includes a signature of somitogenesis that suggests that 72-h human gastruloids show some features of Carnegie-stage-9 embryos3. Our study represents an experimentally tractable model system to reveal and examine human-specific regulatory processes that occur during axial organization in early development.

Gastruloids are three-dimensional aggregates of embryonic stem cells that display key features of mammalian development after implantation, including germ-layer specification and axial organization1-3. To date, the expression pattern of only a small number of genes in gastruloids has been explored with microscopy, and the extent to which genome-wide expression patterns in gastruloids mimic those in embryos is unclear. Here we compare mouse gastruloids with mouse embryos using single-cell RNA sequencing and spatial transcriptomics. We identify various embryonic cell types that were not previously known to be present in gastruloids, and show that key regulators of somitogenesis are expressed similarly between embryos and gastruloids. Using live imaging, we show that the somitogenesis clock is active in gastruloids and has dynamics that resemble those in vivo. Because gastruloids can be grown in large quantities, we performed a small screen that revealed how reduced FGF signalling induces a short-tail phenotype in embryos. Finally, we demonstrate that embedding in Matrigel induces gastruloids to generate somites with the correct rostral-caudal patterning, which appear sequentially in an anterior-to-posterior direction over time. This study thus shows the power of gastruloids as a model system for exploring development and somitogenesis in vitro in a high-throughput manner. This work was supported by an European Research Council Advanced grant (ERC-AdG 742225-IntScOmics), a Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) TOP award (NWO-CW 714.016.001) and the Foundation for Fundamental Research on Matter, financially supported by NWO (FOM-14NOISE01) to S.C.v.d.B., A.A., V.v.B., M.B., J.V. and A.v.O., a Biotechnology and Biological Sciences Research Council (no. BB/P003184/1), Newton Trust (INT16.24b) and Medical Research Council (MR/R017190/1) grant to A.M.A., a Newnham College Cambridge Junior Research Fellowship to N.M. and a studentship from the Engineering and Physical Sciences Research Council to P.B.-J. The Cambridge Stem Cell Institute is supported by core funding from the Wellcome Trust and Medical Research Council; J.N. was funded by the University of Cambridge and K.F.S. by core funding from the Hubrecht Institute. This work is part of the Oncode Institute, which is partly financed by the Dutch Cancer Society. We thank A. Ebbing and M. Betist for the robotized tomo-seq protocol; G. Keller for the Brachyury-GFP cell line; J. Collignon for the Nodal-YFP line; K. Hadjantonakis for the TCF/LEF-mCherry line; S. van den Brink and E. R. Maandag for the E14-IB10 cells; J. Kress and A. Aulehla for the LfngT2AVenus mouse ES cell line; I. Misteli Guerreiro, J. Peterson-Maduro and J. Hoeksma for suggestions for in situ hybridization experiments; W. Thomas, Y. el Azhar, J. Juksar and J. Beumer for reagents and inhibitors; A. de Graaff and A. Stokkermans for help with multiphoton microscopy and analysis of the microscopy data; D. A. Turner for microscopy panels that were used for tomo-seq validation; J. Korving for help with the somite-size measurements in embryos; the Hubrecht FACS facility and R. van der Linden for FACS experiments; Single Cell Discoveries for 10x Genomics scRNA-seq; the Utrecht Sequencing facility for sequencing; and P. Zeller, H. Viñas Gaza, M. Vaninsberghe, V. Bhardwaj and all members of the van Oudenaarden, Sonnen and Martinez Arias laboratories for discussions.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The body plan of the mammalian embryo is shaped through the process of gastrulation, an early developmental event that transforms an isotropic group of cells into an ensemble of tissues that is ordered with reference to three orthogonal axes