Wylie-Heasman Lab

Xenopus Information

	The shape and structure of the embryo, and all cell movements of morphogenesis, require the complex cortical actin skeleton in each embryonic cell.
Below: Xenopus offers an in vivo model system to study the control of actin assembly, since individual proteins can be selectively removed, and the effects on the actin skeleton, and cell behavior studied during morphogenesis.

Selective removal of the two receptors for lysophosphatid acid (LPA) from the blastula cause dramatic reduction of the cortical actin skeleton, and failure of gastrulation movements. This shows that lipid signaling is essential to maintain the normal pattern and density of actin filaments in each cell of the blastula.

Cell and tissue specification. We use Xenopus embryos to identify the molecular pathways leading to formation of the early tissues of the vertebrate body, and their arrangement into the body axes.
		The Xenopus blastula contains stored mRNAs encoding signaling ligands, receptors, and transcription factors, whose action initiates tissue specification. The blastula is patterned by regional positioning, or activation, of these proteins. These can be selectively removed from the egg, allowing us to identify their roles in development.

Development in the absence of the transcription factor VegT causes loss of the endoderm and mesoderm germ layers. The embryo becomes a ball of ectoderm.	Development in the absence of maternal axin, an inhibitor of the Wnt signaling pathway, dorsalizes the embryo (upper row), whilst blockade of Wnt signaling, by removal of ß-catenin, ventralizes the embryo (lower row).	Normal Development
In our current experiments, we are identifying the molecular mechanisms of VegT function leading to mesoderm formation, using genomic and functional analyses. We also study the mechanism of action of the Wnt signaling pathway in axis formation, and the stored maternal mRNAs that control ectoderm formation.