Expression of wntDScer\UAS.cGb, under the control of Scer\GAL4nos.UTR.T:Hsim\VP16, causes ventral invagination defects in gastrulation stage embryos. Approximately one quarter of such embryos have no ventral furrow, while other defective embryos show varying degrees of invagination, which is more defective in the anterior region than the posterior. The mesoderm is largely missing. However, cephalic furrow and germ-band extension occurs normally.