Experimental embryology of gastrulation: pluripotent stem cells as a new model system.

Gastrulation is an inherently complicated process involving a well-orchestrated series of collective cellular behaviours that lead to the emergence of the body plan of the organism. A convenient method to explore the mechanical and chemical interactions that underpin this process, is to isolate specific tissues and to allow them to develop in isolation or in a novel environment. These approaches are the essence of experimental embryology and have enabled an understanding of the underlying principles of embryogenesis, in a way that observation alone could not. The recent rise of 3D culture systems using Embryonic Stem Cells (ESCs) has enabled the extension of this approach to mammalian systems. Here, we argue that these ESC based methods are consistent with the program of experimental embryology, and discuss the insights that can be gained from this perspective, particularly focussing the process of gastrulation and the associated emergence of the body plan.