title: Models for the generation of the embryonic body axes: ontogenetic and evolutionary aspects.
abstract: Coelenterates including hydra are assumed to be close to the last common ancestor before bilaterality evolved. Models based on local self-enhancement and long-range inhibition account for pattern formation and regeneration along this ancestral axis. The body of a hydra-like ancestor evolved into the brain and heart of higher organisms, accounting for the close relationship of both patterning processes. Bilateria require a long-extended organizing region to pattern their dorsoventral axis. Models reveal the difficulties in the generation of such a stripe-like organizer and account for different mechanisms realized in vertebrates and insects. Common pathways involved in hydra budding and in the formation of appendages in higher organisms suggest a possible link.
authors.affiliation: Max-Planck-Institut für Entwicklungsbiologie, Spemannstr. 35, D-72076 Tübingen, Germany. hans.meinhardt@tuebingen.mpg.de
authors.forename: Hans
authors.initials: H
authors.lastname: Meinhardt
mesh_terms: D000818:Animals; D005075:Biological Evolution; D019521:Body Patterning / Q000502:physiology*; D016764:Cell Polarity / Q000502:physiology; D047108:Embryonic Development / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D006829:Hydra / Q000196:embryology*; D008954:Models, Biological; D015398:Signal Transduction / Q000502:physiology