Formation of the early vertebrate embryo depends on a Brachyury/Wnt autoregulatory loop within the posterior mesodermal progenitors. We show that exogenous retinoic acid (RA), which dramatically truncates the embryo, represses expression of the zebrafish brachyury ortholog no tail (ntl), causing a failure to sustain the loop. We found that Ntl functions normally to protect the autoregulatory lo...

Reverse transcription-PCR and Northern and Western blot analyses indicate that mRNA and protein encoded by the Brachyury gene are expressed by the pluripotent human embryonal carcinoma cell line NTERA2 and are only modestly down-regulated during retinoic acid-induced differentiation. This differentiation occurs along a neural lineage, with no obvious evidence of the formation of mesodermal deri...