Positive regulator of Wnt signaling, acting synergistically with dvl2 (By similarity). Functions upstream of ctnnb1/beta-catenin in the canonical Wnt pathway, and also activates jnk in the Wnt/planar cell polarity (PCP) pathway (By similarity). Acts as a non-receptor guanine nucleotide exchange factor which binds to and activates guanine nucleotide-binding protein G(i) alpha (Gi-alpha) subunits (PubMed:30948426). This promotes apical cell constriction and subsequent bending of the neural plate during neurulation via arhgef18 (By similarity). Enriched at apical cell junctions. Undetectable at the gastrula stage at 7.5 hours post-fertilization (hpf) but readily observable during neurulation at 16 and 22 hpf where expression is restricted to the neural rod at 16 hpf and the neural tube at 22 and 28 hpf. The GBA (G-alpha binding and activating) motif mediates binding to the alpha subunits of guanine nucleotide-binding proteins (G proteins). The PDZ domain is required for localization to apical junctions. Impaired hinge point formation in the forebrain and midbrain cavities at 22 hours post-fertilization (hpf) in 95% of embryos (PubMed:30948426). Moderate curvature of the dorsal axis in 35% of embryos at 28 hpf which disappears at later stages (PubMed:30948426). Mild abnormalities in midbrain and forebrain ventricular cavities at 56 hpf (PubMed:30948426). Belongs to the CCDC88 family.