T-box transcription factor T, also known as Brachyury protein, is encoded for in humans by the TBXT gene. Brachyury functions as a transcription factor within the T-box family of genes. Brachyury homologs have been found in all bilaterian animals that have been screened, as well as the freshwater cnidarian Hydra. History The brachyury mutation was first described in mice by Nadezhda Alexandrovna Dobrovolskaya-Zavadskaya in 1927 as a mutation that affected tail length and sacral vertebrae in heterozygous animals. In homozygous animals the brachyury mutation is lethal at around embryonic day 10 due to defects in mesoderm formation, notochord differentiation and the absence of structures posterior to the forelimb bud (Dobrovolskaïa-Zavadskaïa, 1927). The name brachyury comes from the Greek brakhus meaning short and oura meaning tail. In 2018 HGNC updated the human gene name from T to TBXT, presumably to overcome difficulties associated with searching for a single letter gene symbol. The mouse gene has been changed to Tbxt. Tbxt was cloned by Bernhard Herrmann and colleagues and proved to encode a 436 amino acid embryonic nuclear transcription factor. Tbxt binds to a specific DNA element, a near palindromic sequence TCACACCT through a region in its N-terminus, called the T-box. Tbxt is the founding member of the T-box family which in mammals currently consists of 18 T-box genes. The crystal structure of the human brachyury protein was solved in 2017 by Opher Gileadi and colleagues at the Structural Genomics Consortium in Oxford. Role in development The gene brachyury appears to have a conserved role in defining the midline of a bilaterian organism, and thus the establishment of the anterior-posterior axis; this function is apparent in chordates and molluscs. Its ancestral role, or at least the role it plays in the Cnidaria, appears to be in defining the blastopore. It also defines the mesoderm during gastrulation. Tissue-culture based techniques have demonstrated one of its roles may be in controlling the velocity of cells as they leave the primitive streak. It effects transcription of genes required for mesoderm formation and cellular differentiation. Brachyury has also been shown to help establish the cervical vertebral blueprint during fetal development. The number of cervical vertebrae is highly conserved among all mammals; however a spontaneous vertebral and spinal dysplasia (VSD) mutation in this gene has been associated with the development of six or fewer cervical vertebrae instead of the usual seven. Expression In mice T is expressed