Vertebrate embryos are symmetrical with organs deriving from the embryonic midline, but many of these organs develop positional left-right asymmetry during embryogenesis. Mechanisms surrounding embryo orientation are not well defined yet failure to correctly specify the asymmetrical placement/orientation of organs leads to pathologies and severe birth defects, such as heterotaxia. Genetically modified (GM) and reporter mice can be generated and embryos isolated for analysis into the role of particular genes in the development of left-right asymmetry in embryogenesis. These embryos can be used for understanding how mutations in genes responsible for left-right asymmetry can cause pathologies and birth defects.
Why we funded it
This fellowship aims to replace the need for GM mouse embryos in the study of left-right asymmetry during embryogenesis with a novel three dimensional (3D) tissue culture technique.
The generation of novel GM mouse lines can require up to 100 mice per gene of interest. Additional animals are then required for the isolation of embryos to study the impact of these genes on the acquisition of left-right asymmetry in embryogenesis. The use of mouse embryonic stem cells (mESCs) in the newly developed 3D ex vivo model alleviates the need for the development of GM mice as genome editing techniques can be used to manipulate the stem cells directly.
Dr Turner and colleagues from the University of Cambridge have developed a novel tissue culture technique suitable for the purpose of modelling left-right asymmetry in a developing embryo. Small numbers of mESCs are aggregated to form a 3D organoid, termed a “gastruloid” 1,2. Crucially, these gastruloids mimic many of the early events in embryogenesis including left-right asymmetry and the development of a Node-like structure (Nd-LS)3. The Node forms in early embryonic development and is central to the development of asymmetry but the mechanism by which the Node orchestrates these events remains unknown. The aim of this fellowship is to explore the similarities of the Nd-LS and the embryonic Node and the suitability of the gastruloids as an ex vivo system to study early patterning events.
1 Baillie-Johnson, P. et al. (2015). Generation of Aggregates of Mouse Embryonic Stem Cells that Show Symmetry Breaking, Polarization and Emergent Collective Behaviour In Vitro. Journal of visualized experiments : JoVE 105 (53252) doi:10.3791/53252
2 van den Brink, S. C. et al. (2014). Symmetry breaking, germ layer specification and axial organisation in aggregates of mouse embryonic stem cells. Development 141 (22): 4231-4242 doi:10.1242/dev.113001
Beccari et al. (2018). Generating Gastruloids from Mouse Embryonic Stem Cells. Nature Protocol Exchange doi: 10.1038/protex.2018.094
Beccari et al. (2018). Multi-axial self-organization properties of mouse embryonic stem cells into gastruloids. Nature 562:272–276. doi: 10.1038/s41586-018-0578-0
Turner DA et al. (2017). Anteroposterior polarity and elongation in the absence of extra-embryonic tissues and of spatially localised signalling in gastruloids: mammalian embryonic organoids. Development 144:3894-3906. doi: 10.1242/dev.150391
Turner DA (2017). From Organoids to Gastruloids. The Biologist 64(5):14-19. doi: 10.17863/CAM.20824