Transcriptional repressor. Cooperates with vent2 in a ventral signaling pathway downstream of bmp4, which antagonizes the Spemann organizer and dorsal mesoderm formation, and leads to ventral mesoderm formation. Acts downstream of bmp4 to repress transcription of foxa4-B/XFD-1'. Binds to DNA with preference for the target sequence 5'-CTATT[T/C]G-3'. Also binds 5'-TGCATTTTG-3' at a lower frequency, and occasionally 5'-TTGATC-3'. Binds to the homeobox 2 (HBX2) repressor element in the promoter of the myf5 gene and represses myf5 transcription in the ventral domain. Expressed in the ventral marginal zone of gastrulae. At stage 11.5, also expressed in the ventral region of the animal cap (ectoderm). At the end of gastrulation, predominantly localized to the ventral and lateral regions of the closing slit blastopore. At early tail bud stage, expression is maintained only in the forming proctodeum. Expression begins in the late blastula, peaks at state 11 (early gastrula) and decreases thereafter. By bmp4. Suppressed by gsc, acting in a negative cross-regulatory loop. The N-terminal region is required for repressor function.