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Journal Article

Models for patterning primary embryonic body axes: The role of space and time


Meinhardt,  H
Department Integrative Evolutionary Biology, Max Planck Institute for Developmental Biology, Max Planck Society;

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Meinhardt, H. (2015). Models for patterning primary embryonic body axes: The role of space and time. Seminars in Cell & Developmental Biology, 42, 103-117. doi:10.1016/j.semcdb.2015.06.005.

Cite as: https://hdl.handle.net/21.11116/0000-000A-7898-4
Models for the generation and interpretation of spatial patterns are discussed. Crucial for these processes is an intimate link between self-enhancing and antagonistic reactions. For spatial patterning, long-ranging antagonistic reactions are required that restrict the self-enhancing reactions to generate organizing regions. Self-enhancement is also required for a permanent switch-like activation of genes. This self-enhancement is antagonized by the mutual repression of genes, making sure that in a particular cell only one gene of a set of possible genes become activated - a long range inhibition in the 'gene space'. The understanding how the main body axes are initiated becomes more straightforward if the evolutionary ancestral head/brain pattern and the trunk pattern is considered separately. To activate a specific gene at particular concentration of morphogenetic gradient, observations are compatible with a systematic and time-requiring 'promotion' from one gene to the next until the local concentration is insufficient to accomplish a further promotion. The achieved determination is stable against a fading of the morphogen, as required to allow substantial growth. Minor modifications lead to a purely time-dependent activation of genes; both mechanisms are involved to pattern the anteroposterior axis. A mutual activation of cell states that locally exclude each other accounts for many features of the segmental patterning of the trunk. A possible scenario for the evolutionary invention of segmentation is discussed that is based on a reemployment of interactions involved in asexual reproduction.