Slit is mislocalized in how18 and dg62 mutant CBs. (A–C) Dorsal XY views of wild-type (A), how18 (B), and dg62 (C) embryos at stage 16 showing general distribution of Dg and Slit within the cardiac tube. (D–R) Transverse Z views of CBs from wild-type (D–H), how18 (I–M), and dg62 (N–R) embryos at stage 16 stained for Slit and Dg (D–M) and for Slit and Trol (N–R). A′–R′, Slit only; A″–M″, Dg only; N″–R″, Trol only. Slit is strongly expressed at the L domains colocalizing with Dg (A and D–H) during (D) and at the end (E–H) of CB migration. In how18 (B) and dg62 (C), Slit is no longer observed at the L domains and does not colocalize with Dg or Trol, but is rather seen inside the cytoplasm in dense patches during CB migration (e.g., compare D–D″ with I–I″) and after (K–R, K′–R′, and K″–R″, compared with E–H, E′–H′, and E″–H″). Solid and dotted lines show the expected wild-type localization of the L domain. (S) Schematic representation of Slit expression (red) and Dg or Trol (green). During migration (1) and after CB coalescence (2), Slit is expressed in patches inside CB cytoplasm in how or dg mutant instead of being expressed at the L domains as in wild type. Bars, 5 μm.