Patterning the marginal zone of early ascidian embryos: localized maternal mRNA and inductive interactions
Article first published online: 21 JUN 2002
Copyright © 2002 Wiley Periodicals, Inc.
Volume 24, Issue 7, pages 613–624, July 2002
How to Cite
Nishida, H. (2002), Patterning the marginal zone of early ascidian embryos: localized maternal mRNA and inductive interactions. Bioessays, 24: 613–624. doi: 10.1002/bies.10099
- Issue published online: 21 JUN 2002
- Article first published online: 21 JUN 2002
- The Ministry of Education
- Sports and Culture of Japan
Early animal embryos are patterned by localized egg cytoplasmic factors and cell interactions. In invertebrate chordate ascidians, larval tail muscle originates from the posterior marginal zone of the early embryo. It has recently been demonstrated that maternal macho-1 mRNA encoding transcription factor acts as a localized muscle determinant. Other mesodermal tissues such as notochord and mesenchyme are also derived from the vegetal marginal zone. In contrast, formation of these tissues requires induction from endoderm precursors at the 32-cell stage. FGF–Ras–MAPK signaling is involved in the induction of both tissues. The responsiveness for induction to notochord or mesenchyme depends on the inheritance of localized egg cytoplasmic factors. Previous studies also point to critical roles of directed signaling in polarization of induced cells and in subsequent asymmetric divisions resulting in the formation of two daughter cells with distinct fates. One cell adopts an induced fate, while the other assumes a default fate. A simple model of mesoderm patterning in ascidian embryos is proposed in comparison with that of vertebrates. BioEssays 24:613–624, 2002. © 2002 Wiley Periodicals, Inc.