Fig. 3.

fra mutants show diminished adherent domains. TEM sections through the heart of stage 17 wild type (wt) (A), fra³ and unc5⁸ mutant embryos (B) and (C) respectively. In fra³ mutants (B) the area of CB–CB contact is diminished (arrows) and the lumen appears enlarged as compared with wt. In contrast, unc5 mutants (C) are inappropriately adhered along the entire CB face, resulting in the absence of a lumen (arrow). In fra³/+ heterozygotes, Discs large (Dlg), a junctional marker is enriched at the dorsal and ventral sites of CB contact (arrows) (D). In fra³/ fra³ embryos, Dlg fails to accumulate at these points (arrows) (E). In unc5⁸ mutants, Dlg accumulates between CBs that are inappropriately attached (F).