Null mutations cause a ventralization phenotype.
Soon after zen expression is restricted to the dorsal-most regions of the embryonic ectoderm, Race is activated in a coincident pattern and becomes associated with the amnioserosa during germ band elongation, shortening and heart morphogenesis. After germ band elongation, Race is also expressed in both the anterior and posterior midgut, where it persists throughout embryogenesis. Two TGF-beta growth factors, dpp and screw , function synergistically to subdivide the dorsal ectoderm into two embryonic tissues, the amnioserosa and dorsal epidermis. Previous studies have shown that peak dpp activity is required for the localized expression of zen . ZEN in turn directly activates the amnioserosa-specific expression of a downstream target gene, Race .