Fish are like flies are like frogs: Conservation of dorsal-ventral patterning mechanisms
✍ Scribed by Scott A. Holley; Edwin L. Ferguson
- Book ID
- 102759499
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 510 KB
- Volume
- 19
- Category
- Article
- ISSN
- 0265-9247
No coin nor oath required. For personal study only.
✦ Synopsis
Genetic analysis of Drosophila has shown that a morphogenetic gradient of the Transforming Growth Factor$ family member dpp patterns the embryonic dorsalventral axis. Molecular and embryological evidence from Xenopus has strongly suggested a similar role for Bmp-4, the dpp homolog, in patterning the dorsalventral axis of chordates. A recent report has now identified mutations in two genes, din0 and swirl, that disrupt dorsal-ventral patterning in the zebrafish Danio rerio('). Characterization of these mutations parallels findings from Drosophila, thus establishing a genetic framework for the analysis of dorsalventral patterning in a vertebrate.
Molecular and genetic analysis of dorsal-ventral patterning
In one of the most famous experiments in embryology, Hans Spemann and Hilde Mangoldt demonstrated that the dorsal blastopore lip of an amphibian embryo has the capacity to induce a second body axis after transplantation from its normal dorsal location to the ventral side of a recipient embryo. This tissue, termed the organizer, will differentiate into notochord, dorsalize ventral mesoderm and induce overlying ectoderm to adopt a neural fate.
Although these inductive interactions were first characterized in the 1920s, it was not until the 1990s that they began to be understood on a molecular basis(*). Work from a variety of laboratories indicated that dorsal-ventral patterning within the vertebrate mesoderm relies on the antagonistic interaction between dorsalizing and ventralizing signals (Fig. 1). Two genes expressed in the organizer, chordin and noggin, encode novel secreted proteins that have characteristics of the organizer ~i g n a I ( ~3 ~) .
Both proteins can dorsalize ventral mesoderm, induce ectoderm to adopt a neural fate, and restore dorsal structures in embryos that have been ventralized by exposure to ultraviolet light. Conversely, the Bmp-4 gene, a member of the Transforming Growth Factor p