Gastrulation in leech embryos is dominated by the epibolic movements of two tissues: germinal bands, composed of segmental precursor cells, and an overlying epithelium that is part of a provisional integument. During gastrulation, the germinal bands move over the surface of the embryo and coalesce along the prospective ventral midline. Concurrently, the epithelium spreads to cover the embryo. W...

In vitro studies have suggested that proteoglycans facilitate signaling by mammalian growth factors, but genetic evidence supporting this role has been lacking. Here, we characterize the ENU-induced mutation lazy mesoderm (lzme), which disrupts the single mouse gene encoding UDP-glucose dehydrogenase (Ugdh), an enzyme required for the synthesis of the glycosaminoglycan (GAG) side chains of prot...

The recognition that the processes involved in tumour formation are strikingly similar to developmental morphogenetic processes, such as gastrulation, has refashioned our approach to cancer research. Wnt and its receptor Frizzled govern the morphogenetic processes of gastrulation. Directed cell movements during gastrulation require the cells to undergo transient epithelial to mesenchymal transi...

During mouse gastrulation, endoderm cells of the dorsal foregut are recruited ahead of the ventral foregut and move to the anterior region of the embryo via different routes. Precursors of the anterior-most part of the foregut and those of the mid- and hind-gut are allocated to the endoderm of the mid-streak-stage embryo, whereas the precursors of the rest of the foregut are recruited at later ...

We review the early stages of chick embryogenesis, in particular the formation of the hypoblast, and the ingression of endoderm and mesoderm through the primitive streak. The formation of a trilaminar embryo during gastrulation is accompanied by the specification of body axes. The first axis is already present in the unfertilized egg and runs from the cytoplasmatic animal to the yolk rich veget...

In the developing vertebrate embryo, proper dorsal-ventral patterning relies on BMP antagonists secreted by the organizer during gastrulation. The BMP antagonist chordin has a complex interaction with BMPs that is governed in part by its interaction with the secreted protein twisted gastrulation (tsg). In different contexts, tsg has activity as either a BMP agonist or as a BMP antagonist. Using...

Tissue morphogenesis requires assembling and disassembling individual cell-cell contacts without losing epithelial integrity. This requires dynamic control of adherens junction (AJ) positioning around the apical domain, but the mechanisms involved are unclear. We show that atypical Protein Kinase C (aPKC) is required for symmetric AJ positioning during Drosophila embryogenesis. aPKC is dispensa...

We identified cDNAs encoding the Xenopus Smad proteins most closely related to mammalian Smad8, and we present a functional analysis of this activity (also referred to recently as xSmad11). Misexpression experiments indicate that xSmad8(11) regulates pathways distinct from those regulated by the closely related xSmad1. Embryos that develop from eggs depleted of xSmad8(11) mRNA fail to gastrulat...

Vertebrate gastrulation requires coordination of mesoderm specification with morphogenetic movements. While both of these processes require FGF signaling, it is not known how mesoderm specification and cell movements are coordinated during gastrulation. The related Sprouty and Spred protein families are recently discovered regulators of receptor tyrosine kinase signaling. We identified two gene...

Genetic screens in Drosophila designed to search for loci involved in gastrulation have identified four regions of the genome that are required zygotically for the formation of the ventral furrow. For three of these, the genes responsible for the mutant phenotypes have been found. We now describe a genetic characterization of the fourth region, which encompasses the cytogenetic interval 24C3-25...