2 Summary The patterning of many developing tissues is orchestrated by gradients of morphogens. Included among the molecular events that drive the formation of morphogen gradients are a variety of elaborate regulatory interactions. It is widely thought that the purpose of such interactions is to make gradients robust—i.e. resistant to change in the face of genetic or environmental perturbations...

Morphogen gradients are proposed to organise cell fates during development via the long-range activity of secreted molecules. Their existence in vertebrates, however, has been debated. A recent study has identified the Nodal-related protein Squint as a bona fide morphogen in vertebrate mesoderm.

In animal embryos, morphogen gradients determine tissue patterning and morphogenesis. Shyer et al. provide evidence that, during vertebrate gut formation, tissue folding generates graded activity of signals required for subsequent steps of gut growth and differentiation, thereby revealing an intriguing link between tissue morphogenesis and morphogen gradient formation.

The amphibian embryo provides a powerful model system to study morphogen gradients because of the ease with which it is possible to manipulate the early embryo. In particular, it is possible to introduce exogenous sources of morphogen, to follow the progression of the signal, to monitor the cellular response to induction, and to up- or down-regulate molecules that are involved in all aspects of...

Morphogen gradients are concentration fields of molecules acting as spatial regulators of cell differentiation in developing tissues and play a fundamental role in various aspects of embryonic development. We discovered a family of self-similar solutions in a canonical class of nonlinear reaction-diffusion models describing the formation of morphogen gradients. These solutions are realized in t...