The blastulae of unincubated eggs of the quail, Coturnix coturnix japonica, have been bisected in ovo, using the technique of Lutz (1949). Some embryos were harvested after 24 h and found to possess two primitive streaks. Most were fixed at 48 h or 72 h. Some were found to have regulated to form almost normal single axes, whilst others had developed into duplicitas anterior embryos, separate tw...

To elucidate the precise roles of axial structures in the myogenic differentiation of the somite, we have examined the effects of the axial organs' precise spatial position during migration and differentiation of somitic cells by using in vivo transplantation of the neural tube and of the notochord directly into the paraxial mesoderm. Differentiation of myotomal cells was identified through the...

We show here that expression of Hoxa10 in the presomitic mesoderm is sufficient to confer a Hox group 10 patterning program to the somite, producing vertebrae without ribs, an effect not achieved when Hoxa10 is expressed in the somites. In addition, Hox group 11-dependent vertebral sacralization requires Hoxa11 expression in the presomitic mesoderm, while their caudal differentiation requires t...

The role of paraxial mesoderm or the somites in decision of ectoderm to acquire the neuroepithelial fate and its subsequent diversification to functional neural subtypes especially in mammalians is obscure. Here we report, for the first time, the influence of the co-culture of alginate bead-encapsulated somites isolated from chick embryos on neural differentiation in mouse embryonic stem cells-...

In amniotes, it is widely accepted that WNTs secreted by the dorsal neural tube form a concentration gradient that regulates early somite patterning and myotome organization. Here we demonstrate in the chicken embryo that WNT protein is not secreted to act at a distance, but rather loaded onto migrating neural crest cells that deliver it to somites. Inhibiting neural crest migration or ablating...

The zebrafish zisp gene encodes a putative transmembrane protein with a DHHC zinc finger motif. At the segmentation period zisp is expressed in the adaxial cells and the somites in a striping pattern. The zisp transcripts are localized to the posterior parts within the individual somites. In fused somites mutants, zisp is expressed throughout the somitic mesoderm. These expression patterns are ...

Somitogenesis in the mouse embryo commences with the generation of presumptive somitic mesoderm at the primitive streak and in the tail-bud mesenchyme. The presumptive somitic mesoderm is then organized into somite primordia in the presomitic mesoderm. These primordia undergo morphogenesis leading to the segmentation of somites at the cranial end of the presomitic mesoderm. Somite sizes at the ...

The distribution of the extracellular matrix (ECM) glycoprotein, tenascin, has been compared with that of fibronectin in neural crest migration pathways of Xenopus laevis, quail and rat embryos. In all species studied, the distribution of tenascin, examined by immunohistochemistry, was more closely correlated with pathways of migration than that of fibronectin, which is known to be important fo...