The mammalian body plan blueprint, an in vitro approach

Project Information

MiniEmbryoBlueprint

Grant agreement ID: 834580

DOI

10.3030/834580

Project closed

EC signature date 30 April 2019

Start date 1 October 2019

End date 30 September 2025

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 2 480 300,00

EU contribution

€ 2 480 300,00

Coordinated by

UNIVERSIDAD POMPEU FABRA
Spain

Periodic Reporting for period 4 - MiniEmbryoBlueprint (The mammalian body plan blueprint, an in vitro approach)

Reporting period: 2024-02-01 to 2025-09-30

Summary of the context and overall objectives of the project

The main objective of the project is to understand the interplay between mechanical and chemical signalling in the emergence and elaboration of the mammalian body plan with a focus on gastrulation, the process that transforms the mass of cells that results from the cleavage of the zygote into the animal body plan. Gastrulation is a central process in animal development and appears to be a weak point in the development of an embryo and the origin of several diseases and conditions. Developing models of this process will open the door to modelling and thereby understanding and addressng possible treatments.
The gastruloid system has proven an excellent model system of gastrulation and one that has shown to reduce the use of animals in research. At this, the system has a strong impact on the 3Rs (Replacement, Reduction and Refinement) in the use of animals in research. Most significantly, we have shown that we can obtain gastruloids from human ES cells and this has opened up an avenue to explore the early stages of human development, something that has remained impossible to do. This is turn will allow disease modelling of multiple neonatal conditions. An important aspect of gastruloids is the fact that they are compliant with all ethical rules of research with human embryos. The project does not include working with human gastruloids but an request has been made to do this on the grounds of the significance and potential of the research.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

There are two clear phases to mammalian gastrulation each associated with a track of the primitive streak. The first one leads to the specification of anterior fates including the endoderm, craniofacial elements and the heart. A second phase, promotes axial elongation and fates associated with the trunk. Molecular work has shown that the anterior primitive streak is dependent on a GRN driven by Eomesodermin, whereas the posterior one depends on a different GRN driven by TbxT. Using gastruloids we have shown that these GRNs are independent. Furthermore, our work has revealed that each is driven by a different signal: Nodal for the Eomesodermin GRN and Wnt for the TbxT GRN. Using specific signalling regimes in gastruloids we can generate either the anterior or the posterior primitive streak suggesting that they are independent molecular modules. Our experimental system has allowed us to explore the relationship between the two modules and shown that gastrulation starts with high levels of Nodal and low levels of Wnt and that this relationship is inverted over time. allow. The inversion is driven by a cross inhibitory interactions of the two signalling molecules. The different fates and their sequence are dictated by the relative levels of Nodal and Wnt. Analysis of gene expression in mouse embryos shows that this relationship is associated with gastrulation. Furthermore, the transition from one module to another is associated with the suppression of Nodal signalling and we have shown that this is the case in gastruloids.
Analysis of gene expression in embryos of different species has shown that the two modules are conserved in all amniotes and that in all cases the transition coincides with the decay of Nodal signalling and the increase in Wnt signalling. This indicates that the two modules represent a conserved and universal feature of amniote gastrulation. Furthermore, we have shown the existence and function of both modules in human gastruloids, suggesting that they are likely to be functional in human embryos.
Additional outputs of the project are
• The standardization of the gastruloid culture that is now widely used to study early mammalian development with a significant reduction in the number of animals in experiments.
• A major contribution to the development of a replica model of primate gastrulation in a collaboration with Zhen Liu in Shanghai (China).
• Collaborations that have shown how gastruloids are a platform for disease modelling during somitogenesis and early blood formation.
• Significant contributions to the development of standards and an ethical framework for the field of stem cell based embryo models.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The project has identified a universal mechanism for mammalian gastrulation and established gastruloids as a useful system for basic and applied research.
The results are being extrapolated to human gastruloids where they can be used to establish platforms for disease modelling and drug screening.

Comparison of organization and gene expression in gastruloids and embryos.