Immunohistochemical analysis of the Brachyury protein in wild-type and mutant mouse embryos.
The murine Brachyury (T) gene is required in posterior mesoderm formation and axial development. Mutant embryos lacking T gene function are deficient in notochord differentiation and posterior mesoderm formation, but make anterior mesoderm. Posterior axial development requires increasing T activity along the rostrocaudal axis. The T gene is transiently transcribed in nascent and migrating mesoderm and continuously in the notochord. The maintenance of T expression in the notochord depends, directly or indirectly, on wild-type T activity. In Xenopus it has been shown that the onset of T expression occurs in response to mesoderm-inducing growth factors. The T protein is binding to DNA and is probably involved in the control of gene expression. Here we show that the T protein is located in the nucleus. We have analyzed the expression pattern of T protein in wild-type and mutant embryos from early primitive streak formation to the end of the tail bud stage. Throughout all stages of mesoderm formation T protein is transiently present in nascent and migrating mesoderm. In the notochord T protein persists to the end of the tail bud stage. It is also transiently detectable in the forming gut endoderm and in prospective neuroectoderm of later embryos. This shows that T expression is not strictly correlated with a commitment of cells to mesoderm. The analysis of the tail development of TWis/+ mutant embryos demonstrated that the formation of the neural tube, gut, and somites from the tail bud proceeds in the absence of a notochord. The maintenance and differentiation of these structures, however, seems to depend on signals from the notochord.
Kispert
A
A
Max-Planck-Institut für Entwicklungsbiologie, Abteilung Biochemie, Tübingen, Germany.
Herrmann
B G
BG
D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000032:analysis* / Q000502:physiology; D004622:Embryo, Mammalian / Q000737:chemistry*; D005314:Embryonic and Fetal Development; D005260:Female; D005326:Fetal Proteins / Q000032:analysis* / Q000502:physiology; D007150:Immunohistochemistry; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D011247:Pregnancy; D020825:T-Box Domain Proteins; D000098908:Brachyury Protein
D004268:DNA-Binding Proteins; D005326:Fetal Proteins; D020825:T-Box Domain Proteins; D000098908:Brachyury Protein