Fig. 4. Ectopic Ttk69 expression blocks glial development. Expression of the glial marker Gcm, revealed using the enhancer-trap line rA87 (A), and Repo (B) is inhibited by early Ttk69 expression using the Kr-Gal4 driver. Later expression of Ttk69 in the progeny of glioblasts using the sca-Gal4 driver also blocks glial development. (C) In stage 12 wild-type embryos, anti-Repo antibody staining (in green) stains between 13-15 glial cells per hemineuromere. (D) After ectopic expression of Ttk69 (revealed in red), the Repo-positive glial number is reduced to two to three cells per hemineuromere. The remaining glia are some longitudinal glia (arrows) and the glioblast 3-1 (asterisk) (E) Expression of a nuclear-targeted lacZ driven by sca-Gal4 initially is low in the longitudinal glia (arrowhead, stage 11) but later increases (arrowhead, stage 13). Other glia such as cell body glia (arrows) express high levels of lacZ from the first. (F-G) Anti-Repo staining shows that overexpression of Ttk69 using MZ1580-Gal4 reduces longitudinal glial number in the fully-formed stage 15 embryonic CNS (arrows in G; compare with control F). Anterior is upwards; open arrow, midline; lg, longitudinal glia.