Fig. 4. Tissue-specific engulfment in wild-type, H99 and p35-expressing cells. Brain neuronal precursors were marked by photoactivation of a UAS-GFP transgene in different genetic backgrounds. The embryos were injected with caged GAL4VP16 and VGAL, photoactivated in a five- to eight-cell patch of the head neuroectoderm and followed by time-lapse microscopy. The engulfing macrophages are outlined with a thin white line. (A-C) A projection of four 6 µm optical sections of a UAS-nGFP embryo with the GFP fluorescence (A), VGAL fluorescence (B) and a composite of both fluorescent channels (C). (D-F) A projection of three 5 µm optical sections of a UAS-p35; UAS-cGFP embryo with the GFP fluorescence (D), VGAL fluorescence (E) and a composite of both fluorescent channels (F). (G-I) A projection of eight 5 µm optical sections of a UAS-p35/UAS-nGFP embryo with the GFP fluorescence (G), VGAL fluorescence (H) and a composite of both fluorescent channels (I). In the GFP channel, the contrast of several regions was adjusted to equalize the fluorescence of marked epidermal and the brain cells to show their location. In G-L, epidermal cells are outlined with a dashed line and labeled `E'; brain neurons are outlined with a dotted line and labeled `B'. (J-L) A projection of four 5 µm optical sections of a UAS-nGFP; H99 embryo with the GFP fluorescence (J), VGAL fluorescence (K) and a composite of both fluorescent channels (L).