Positive regulator of Wnt signaling, acting synergistically with dvl2/dsh (PubMed:16026968). Functions upstream of ctnnb1/beta-catenin in the canonical Wnt pathway, and also activates jnk in the Wnt/planar cell polarity (PCP) pathway (PubMed:16026968). Acts as a non-receptor guanine nucleotide exchange factor which binds to and activates guanine nucleotide-binding protein G(i) alpha subunits (PubMed:30948426). This promotes apical cell constriction and subsequent bending of the neural plate during neurulation via arhgef18 (PubMed:30948426). Interacts with dvl2/dsh via the PDZ-binding motif. Enriched at apical cell junctions. Expressed weakly in gastrulae, with slightly stronger expression in the dorsal region. In neurulae, expressed in the neural plate with strong expression in the presumptive mesencephalic region. At the tailbud stage, expressed in somatic cells and in part of the tail. Also strongly expressed in regions of the head including eye vesicles, otic vesicles, olfactory placode and the pharyngeal cavity. Expressed in all developmental stages, with a gradual increase in expression from the 2-day tadpole stage onward. The GBA (G-alpha binding and activating) motif mediates binding to the alpha subunits of guanine nucleotide-binding proteins (G proteins) (PubMed:30948426). Both motifs are required for binding and activation of alpha subunits (PubMed:30948426). The PDZ domain is required for localization to apical junctions. Morpholino knockdown does not affect embryo morphology up to gastrulation but causes a delay in the closure of the neural tube (PubMed:30948426). After the neural tube closes, embryos display mild axis curvature and head defects at later stages and malformations are also evident in the embryonic brain which forms a closed structure but displays an enlargement of the ventricles (PubMed:30948426). Embryos show impaired apical constriction of neuroepithelial cells during neurulation (PubMed:30948426). Belongs to the CCDC88 family.