The International Journal of Developmental Biology

Int. J. Dev. Biol. 40: 279 - 289 (1996)

Vol 40, Issue 1

Special Issue: Developmental Biology in Germany

Factors responsible for the establishment of the body plan in the amphibian embryo

Published: 1 February 1996

H Grunz

Universität GH Essen, FB 9 (Biologie), Department of Zoophysiology, Germany. h.grunz@uni-essen.de

Abstract

A central topic of embryology is the establishment of the body plan during embryogenesis. Starting with maternal factors distributed in the early cleavage stages in distinct patterns and gradients cell-to-cell interactions including early embryonic induction result in the formation of mesoderm and the organizer area. While many facts are known about the role of growth factors like activin (closely related to the vegetalizing factor), processed Vg1, BMPs and FGF for mesoderm formation, the establishment of the central nervous system is not yet well understood. However, there is growing evidence that neural induction is a multistep process at the level of the dorsal mesoderm (organizer) and the reacting neuroectoderm. Therefore the existence of only one neuralizing factor is unlikely. We report about data that follistatin protein is not a direct neural inducer. Furthermore our comparative studies of Xenopus and Triturus exogastrulae indicate that planar signals are unlikely in the Triturus embryo (urodeles) during the early steps of neural induction. Vertical signals emanating from the chordamesoderm are essential for the terminal neuralization and regionalization of the central nervous system during gastrulation for both Xenopus and Triturus. The putative role of neuralizing factors and BMP/activin-like molecules for the stabilization or shift of neuroectoderm into different pathways of differentiation (epidermis or neural default state) is discussed.

Full text in web format is not available for this article. Please download the PDF version.