Required for head formation during gastrulation. Functions as an inhibitor for the caudalizing signals wnt and fgf, does not inhibit bmp, activin and nodal signaling in head formation process. Induces retention of fzd8 in the endoplasmic reticulum and inhibits trafficking of fzd8 to the cell surface. Interacts with immature forms of fzd8 and fgfr. Expressed in the prospective head ectoderm and the Spemann organizer at gastrula stage. Expression increases during gastrulation and decreases during early neurulation. As gastrulation progresses, expression occurs in the anterior neuroectoderm, after mid-gastrulation, expressed in the superficial layer. The expression in endomesoderm concomitantly becomes restricted to the future prechordal plate territory. At the mid-neurula stage, the ectodermal expression declines, while that in the prechordal plate persists until the late-neurula stage. 'Shisa' was named after a sculpture form, common to southern Japan, with a large head similar to the Egyptian sphinx. Belongs to the shisa family.