Fig. 2. NotchIC induces cell fate changes in the neurogenic ectoderm. Transgenic embryos express the stripe2-NotchIC fusion gene and were hybridized with sim or snail antisense RNA probes. (A) The transgene induces the ectopic sim pyramid pattern prior to the onset of the endogenous pattern in the mesectoderm. (B) The ectopic sim pattern is maintained during gastrulation. By this stage sim expression extends into dorsal regions. The endogenous expression pattern is also observed. (C) After gastrulation, the two lines of sim expression converge at the ventral midline to form the mesectoderm. There is also a broad domain of ectopic staining that probably arises from the ectopic pyramid seen in younger embryos. Ectopic sim expression leads to a loss of identifiable neurons, as judged by the snail expression pattern (D). (D) The snail expression pattern is altered in delaminating neuroblasts during germ band elongation. There is a gap in the presumptive ventral nerve cord that coincides with the ectopic sim expression pattern (see C).
