In early Xenopus embryos, the prototypical XFast-1/Smad2/Smad4 complex ARF1 is induced at the Mix.2 ARE by activin overexpression. We have characterised ARF2, a related, but much more abundant, complex formed during gastrulation in response to endogenous TGFbeta family members and we have identified a novel Fast family member, XFast-3, as its transcription factor component. Endogenous ARF2 effi...

The heart arises from distinct sources of cardiac progenitors that independently express Mesp1 during gastrulation. The precise number of Mesp1 progenitors that are specified during the early stage of gastrulation, and their clonal behavior during heart morphogenesis, is currently unknown. Here, we used clonal and mosaic tracing of Mesp1-expressing cells combined with quantitative biophysical a...

Haeckel's studies of development in calcareous sponges (1872) led him to develop the "Gastraea Theory," which proposes that the ancestral mode of germ layer formation, or gastrulation, was by invagination to produce a functional gut. His observations that gastrulation in the Calcarea occurs by invagination of a ciliated larva upon settlement and metamorphosis were supported by remarkable photom...

We have isolated a member of the HNF-3/forkhead gene family in ascidians as a means to determine the role of winged-helix genes in chordate development. The MocuFH1 gene, isolated from a Molgula oculata cDNA library, exhibits a forkhead DNA-binding domain most similar to zebrafish axial and rodent HNF-3beta. MocuFH1 is a single copy gene but there is at least one other related forkhead gene in ...

During mouse gastrulation, cells in the primitive streak undergo epithelial-mesenchymal transformation and the resulting mesenchymal cells migrate out laterally to form mesoderm and definitive endoderm across the entire embryonic cylinder. The mechanisms underlying mesoderm and endoderm specification, migration, and allocation are poorly understood. In this study, we focused on the function of ...