Expression of grhScer\UAS.cHa in the amnioserosa under the control of Scer\GAL4c381 or Scer\GAL4332.3 is sufficient to block dorsal closure in 100% and 50% of embryos, respectively. Defects are evident from stage 14-16. The amnioserosa is less contracted than in wild-type and contains cells with abnormal morphology. The epidermal edges fail to meet at the poles during dorsal closure. In embryos over-expressing grhScer\UAS.cHa under the control of Scer\GAL4c381, there are large variations in shape and size of amnioserosa cells, and the contacts with adjacent dorsal epidermis cells is dramatically different. Some epidermal cells expand contact with an amnioserosa cell at the expense of neighbouring cells which become bunched together.
The visceral and dorsal branches of the tracheal system only form rudimentary buds in embryos expressing grhScer\UAS.cHa under the control of Scer\GAL4btl.PS, and the dorsal and lateral trunk branches in each hemisegment remain unconnected at stage 16. Fusion cell differentiation is not affected, but they fail to form interconnecting sprouts. No secondary branch lumen is formed. The basolateral projections of tracheal cells are unaffected in these embryos, but their apical surface does not elongate to form a branch. Expression of grhScer\UAS.cHa under the control of Scer\GAL4bs-23.26 prevents the formation and elongation of the intracellular lumen in terminal cells of the tracheal system.