Fig. 6. Reporter gene expression shows genetic rescue of commissural axonal projections in the lab^–/– cells of the tritocerebrum by transgenic expression of the Lab, Dfd, Antp and Ubx proteins (B-E), and failure of rescue by transgenic expression of the Abd-B protein (F); also shown is the absence of commissural axonal projections in the tritocerebral lab-null mutant domain (A). Laser confocal microscopy of stage 13-15 embryos, reconstructions of optical sections, frontal views. Immunolabeling with anti-ß-gal (green). UAS::taulacZ reporter gene expression is seen in the cortical cytoskeleton and axons of cells in tritocerebral lab mutant. Arrowheads indicate presence or absence of commissural axons of the lab^–/– cells. In A, visualization of cell bodies and axonal projections was by lab::Gal4 driven UAS::taulacZ reporter gene expression in the tritocerebral lab mutant domain. In B-F, visualization of cell bodies and genetic rescue of axonal projections of the lab^–/– cells was through co-expression of UAS::taulacZ reporter with UAS::Hox responders in the tritocerebral lab mutant domain by the lab::Gal4 driver. For all of the Hox gene products except Abd-B these experiments demonstrated that the rescued tritocerebral lab^–/– cells were able to extend axons that projected correctly along the rescued tritocerebral commissure.