Wylie-Heasman Lab

A transgenic line of mice has been developed in which all the cells of the early germ line express the fluorescent protein GFP. This allows the direct visualization of the germ cells, in the living embryo, as they migrate to the sites where the gonads will form. The roles of individual genes in embryonic cell migration can be studied by introducing targeted mutations into this line of mice. You can view a QuickTime movie (1.9 MB), produced by Jim Stallock. (Requires QuickTime player. Download the QuickTime player for PC or Macintosh from Apple.)

Anderson, R.; Faessler R.; Georges-Labouesse, E.; Hynes, R.; Bader, R.; Kreidberg, J.; Schaible, K; Heasman, J.; Wylie C. Mouse primordial germ cells lacking 131 integrin enter the germ line but fail to migrate normally to the gonads. Development 1999; 126:1655-1664.

Wylie, C. Germ Cells Cell 1999; 96:165-174.

Xenopus embryos are used to study the roles of individual genes in early vertebrate development. Individual mRNAs are targeted in the egg by antisense injections. The eggs are then color-coded before fertilization, using vital dyes, to distinguish between different treatments. The embryos retain the dyes until early development is over, and a recognizable body plan is established. The effects of knocking out individual genes can be assayed by morphology and by molecular analysis.

Xanthos, J. B.; Kofron, M.; Wylie, C.; Heasman, J. Maternal VegT is the initiator of a molecular network specifying endoderm in Xenopus laevis. Development, 2001; 128:167-180.

Kofron M.; Demel T.; Xanthos J.; Lohr J.; Sive H.; Osada S-1.; Wright C.; Wylie C.; Heasman J. Mesoderm induction in Xenopus is a zygotic event regulated by maternal VegT via TGFI3 growth factors. Development 1999; 126:5759-5770.

Zhang, J.; Houston, D.; King, M.; Payne, C.; Wylie, C.; Heasman, J. The role of maternal VegT in establishing the primary germ layers in Xenopus embryos. Cell 1998; 94:1-10.

Axin is a cytoplasmic protein thought to play a role in the wnt signaling pathway. Removal of the axin mRNA from the egg causes the embryos to become "dorsalized." Blue embryos are axin depleted and brown are wild-type siblings. Most of the embryo forms dorsal structures, such as head and notochord, at the expense of ventral structures.

Kofron, M; Klein, P; Zahng, F; Houston, D; Schaible, K; Wylie, C. Heasman, J. The role of maternal axin in patterning the Xenopus embryos. Dev. Biol., 2001; 237:183-201.

Beta-catenin is a cytoplasmic protein involved in the wnt signaling pathway. Removal of beta-catenin from the egg caused embryos to become vetralized. No dorsal structures form. This work demonstrated that the wnt signaling pathway is essential for formation of dorsal structures in vertebrates.

Heasman, J.; Kofron, M.; Wylie, C. Beta-catenin signaling activity dissected in the early Xenopus embryo: a novel antisense approach. Dev. Biol. 2000; 222:124-134.

Wylie, C.; Kofron, M.; Payne C.; Anderson R.; Hosobuchi M.; Joseph E.; Heasman, J. Maternal ß catenin establishes a dorsal signal in early Xenopus embryos. Development 1996; 122 2987-2996.

The roles of individual cytoskeletal elements can be studied too. Cytoplasmic movements in the Xenopus egg establish the very first differences between embryonic cells, which later are amplified by cell signaling. Removal of a single microtubule motor protein, Xklp1, from the egg, abrogates the normal movements of germ plasm (red dye) in the egg, which normally takes place within a dense network of microtubules (green dye) in the cortex of the egg.

Robb, D.; Heasman, J.; Raats, J.; Wylie, C. A kinesin-like protein is required for germ plasm aggregation in Xenopus. Cell 1996; 87:823-831.