Involved in dorsal-ventral patterning. Appears to function predominantly as a ventralizing factor, through its actions as a BMP signaling agonist, acting through both chd-dependent and chd-independent mechanisms. May also antagonize BMP signaling, probably via formation of ternary complexes with chd and BMPs, resulting in dorsalization. Expressed uniformly in early embryos. Morpholino knockdown in embryos exhibits variable outcome. It may result in a weak ventralized phenotype (PubMed:11260716) or in dorsalization (PubMed:15525664 and PubMed:15604098). Belongs to the twisted gastrulation protein family.