Control of somitic expression of tenascin in Xenopus embryos by myogenic factors and Brachyury.
Tenascin is a large glycoprotein which is expressed in a restricted pattern in the extracellular matrix (ECM) of vertebrate embryos. Tenascin interferes with cell-fibronectin interactions in vitro, and may play a role in the control of cell migration and differentiation during development. In Xenopus, tenascin immunoreactivity is first detected at the early tailbud stage in the ECM of the most anterior somite. Thereafter, it is distributed dorsally along neural crest cell migration pathways. In this paper, we report that tenascin mRNA is most abundant in dorsal mesoderm at the neurula stage and in somites at the early tailbud stage, indicating that the initial accumulation of tenascin in the ECM is due to secretion from paraxial mesoderm. To understand how tenascin expression in somitic mesoderm is controlled, we have expressed Xbra and the myogenic factors XMyoD and XMyf5 in blastula animal cap tissue. The tenascin gene is activated by all three transcription factors. Interestingly, expression of tenascin mRNA, and accumulation of the protein in the ECM, can occur without formation of muscle. Our results suggest that tenascin regionalization in early Xenopus embryos depends on tenascin RNA expression by somitic mesoderm, where it is likely to be activated by myogenic factors.
Umbhauer
M
M
CNRS URA 1135, Université Pierre et Marie Curie (Paris 6), France.
Riou
J F
JF
Smith
J C
JC
Boucaut
J C
JC
D000818:Animals; D015816:Cell Adhesion Molecules, Neuronal / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D005314:Embryonic and Fetal Development; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism*; D005326:Fetal Proteins / Q000378:metabolism / Q000502:physiology*; D005786:Gene Expression Regulation; D008648:Mesoderm / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism; D009132:Muscles / Q000196:embryology*; D017570:MyoD Protein / Q000378:metabolism; D051787:Myogenic Regulatory Factor 5; D009419:Nerve Tissue Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020825:T-Box Domain Proteins; D019063:Tenascin; D014018:Tissue Distribution; D015534:Trans-Activators; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000196:embryology*; D000098908:Brachyury Protein
D015816:Cell Adhesion Molecules, Neuronal; D004268:DNA-Binding Proteins; D016326:Extracellular Matrix Proteins; D005326:Fetal Proteins; D009124:Muscle Proteins; D017570:MyoD Protein; D051787:Myogenic Regulatory Factor 5; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D020825:T-Box Domain Proteins; D019063:Tenascin; D015534:Trans-Activators; D029867:Xenopus Proteins; D000098908:Brachyury Protein; C497419:Myf5 protein, Xenopus