Fig. 5. Segregation of Pros by Numb and Notch in the LG.

The LG are visualized with either anti-βgal (red or green) in LG-lacZ reporter (B,C,D) or as indicated. (A, A’) Pon (cyan in A and single channel A’) in wild type at stage 16, is present in midline cells but absent from the LG (visualized with anti-Repo, magenta). (B,B’) Numb in wild type at stage 13/14. Numb is upregulated in the LG that migrate posteriorly after dividing (arrowheads) and it is downregulated in the anterior six LG (there are a total of eight LG in this cluster). (C) Pros (green) is present in nine LG instead of six in a numb mutant embryo. There are two LG that do downregulate Pros (10,11). (D) Wild type Pros (magenta) at stage 16, restricted to the six anterior LG. (E,E’) βgal in Su(H)lacZ (green or alone in E’) and Pros (magenta, colocalisation in white) in wild type in the six anterior LG only at stage 16. (F) Lower magnification view of a wild-type embryo as in (E), to show three whole segments. (G) βgal (green) and Pros (magenta) in a pros mutant embryo bearing the Su(H)lacZ reporter. Pros stains axons nonspecifically, but the LG staining is missing and so is Su(H)lacZ in the LG (asterisks indicate location where Pros and β-gal should be). Three segments shown, as in (F). Su(H)lacZ (green) is clearly present at the midline. (H) The distribution of Pros and Notch (green) and Numb (blue) in the LG following the last divisions. At the 4-LG stage all LG contain Numb, Pon, Notch and Pros. As the LG divide, they migrate posteriorly, upregulate Numb and downregulate Pros. The six anterior LG upregulate Pros and Notch and downregulate Numb. Pon is no longer present after the 4-LG stage (stage 13). Anterior is up. (A’,B’,E’) are single channel images. (A-E) show one hemisegment (midline to the left) and (F,G) show three segment images.