Figure 2.

Regulation of sim expression by Notch signaling. In situ hybridization of wild-type (A–C) and Notch mutant (D–F) embryos showing the distribution of sim transcripts at stages 5 (A,D), 6 (B,E), and 8 (C,F). (A,B) Expression of sim was detected in a single row of mesectodermal cells in wild-type embryos [ventrolateral (A) and ventral (B) views]. Accumulation of sim transcripts at the posterior pole is out of focus. (C) Expression of sim in midline cells in a wild-type stage 8 embryo (ventral view). (D,E) In Notch mutant embryos, the expression of sim was restricted to a few cells in the mesectoderm. High levels of sim transcripts were seen at the posterior pole [ventrolateral (D) and ventral (E) views]. (F) The expression of sim was detected in very few midline cells in Notch mutant embryos at stage 8 (ventral view). Two null mutant alleles of Notch, N^55e11 (D–F) and N⁵⁴¹⁹ (not shown), were used in this study and gave similar results. In A–F anterior is to the left.