Transcriptional repressor. Expression begins in the newly forming dorsal mesoderm and is maintained during gastrulation at the dorsal blastopore lip (Spemann organizer). At the early neurula stages, expressed in a row of cells along the dorsal midline that are destined to become the fllor plate of the neural tube. At late neurula, expressed within the anterior and posterior poles of the embryo. After neural closure, expression is detected only in the tailtip, the otic vesicle and at the midbrain/hindbrain boundary.