In developing vertebrate embryos, Pax3 is expressed in the neural tube and in the paraxial mesoderm that gives rise to skeletal muscles. Pax3 mutants develop muscular and neural tube defects; furthermore, Pax3 is essential for the proper activation of the myogenic determination factor gene, MyoD, during early muscle development and PAX3 chromosomal translocations result in muscle tumors, provid...

Teleost fish exhibit remarkable diversity in morphology, such as fins and coloration, particularly on the dorsal side. These structures are evolutionary adaptive because their back is highly visible to other individuals. However, owing to the late phenotypic appearance (from larva to adult) and lack of appropriate mutants, the genetic mechanisms that regulate these dorsoventrally asymmetric ext...

During vertebrate development, the primary body axis elongates towards the posterior and is periodically divided into somites, which give rise to the vertebrae, skeletal muscles and dermis. Somites form periodically from anterior to posterior, and the anterior somites form in a more rapid cycle than the posterior somites. However, how this anteroposterior (AP) difference in somitogenesis is gen...

Light and electron microscopy are used in this study to compare chondrogenesis in cultured somites with vertebral chondrogenesis These studies have also characterized some of the effects of inducer tissues (notochord and spinal cord), and different nutrient media, on chondrogenesis in cultured somites Somites from stage 17 (54-60 h) chick embryos were cultured, with or without inducer tissues, ...

The patterning and differentiation of cells in the somitic mesoderm is an important step in the development of axial structures that include the vertebral column and skeletal muscle. Development of the somitic mesoderm is characterized by the progressive segmentation of mesoderm tissue directly flanking the neural tube into two bilateral rows of somites. Somites when they first appear consist o...

The cell movements and contacts in somite formation in Xenopus are unusual. The vertebrate somite as seen in section is traditionally described as a rosette and is formed by pinching off a group of cells from the paraxial mesoderm; these cells then increase intercellular contacts. Typical rosettes with cells radiating from the myocoel may be seen in the Axolotl (Fig. 1 A). Not all the cells of ...

The formation of somites involves the subdivision of segmented presomitic mesoderm into segmentally arranged somite blocks. In mice and chicks, the basic-helix-loop-helix (bHLH) gene, paraxis, is involved in this process. Here, we report the isolation of a zebrafish homologue of paraxis, par1. par1 is expressed in presomitic paraxial mesoderm from late gastrula stages, and expression is maintai...

The Paraxis gene encodes a basic helix-loop-helix (bHLH) transcription factor expressed in paraxial mesoderm and whose mutant displays an inability to form epithelial somites. We analyzed the later expression pattern of Paraxis transcripts in the chick limb. Paraxis transcripts are located in the Pax3-expressing myoblasts migrating from the somites and persist in proliferating myoblasts in the ...

Quail grafts of Hensen's node were examined for their potential to induce somites in chick blastoderms. The origin of the structures induced depended on the distance of the graft from the host's midline. Nodes placed at the margin of the area pellucida resulted in structures differentiated from the cells of the graft, whereas medially the graft organized host cells to form rows of somites. The ...