Brachyury is expressed in gastrulating bovine embryos well ahead of implantation

Brachyury is a T-box-containing transcription factor involved in mesoderm formation during vertebrate gastrulation. To analyse whether the regulation of gastrulation varies as much as the timing of gastrulation does with respect to implantation, we isolated a bovine brachyury cDNA fragment. The amino acid sequence shows high similarity to mouse and human Brachyury and clear differences to other T-box genes. Whole-mount in situ hybridisation reveals a normal expression pattern except for a transiently reduced expression in the anterior part of the primitive streak. According to these results, gastrulation in mammals is implemented and regulated irrespective of implantation.