Brachyury

The brachyury mutation was first described in mice by Nadine Dobrovolskaïa-Zavadskaïa in 1927 as a mutation that affected tail length and sacral vertebrae in heterozygous animals and is lethal in homozygous animals around embryonic day 10 due to defects in mesoderm formation, notochord differentiation and the absence of structures posterior to the forlimb bud (Dobrovolskaïa-Zavadskaïa, 1927). The name brachyury comes from the Greek brakhus meaning short and oura meaning tail.

According to human and mouse genome nomenclature, brachyury now has the symbol and gene name T although brachyury is maintained as the gene description.

The mouse T gene was cloned by Bernhard Herrmann and colleagues (Herrmann et al., 1990) and proved to encode an 436 amino acid embroynic nuclear transcription factor. T binds to a specific DNA element, a near palindromic sequence TCACACCT through a region in its N-terminus, called the T-box. T is the founding member of the T-box family which in mammals currently consists of 18 T-box genes.



Function
Transcription of genes required for mesoderm formation and cellular differentiation.

Expression
In mice T is expressed in the inner cell mass of the blastocyst stage embryo (but not in the majority of mouse embryonic stem cells) followed by the primitive streak (see image). In later development expression is localised to the node and notochord.

In Xenopus laevis Xbra (the Xenopus T homologue, also recently renamed t) is expressed in the mesodermal marginal zone of the pre-gastrula embryo followed by localisation to the blastopore and notochord at the mid-gastrula stage.

The Danio rerio homologue is known as ntl (no tail)

Cancer
Expression of the brachyury gene has been identified as a definitive diagnostic marker of chordoma, a malignant tumour typically occurring along the spinal cord. This confirms the hypothesis that chordoma arise from cells related to the notochord.