Figure 3

Expression of Nrg in (a, c, e) wild-type, (b) mutant rescue, (d) over-expression and (f) mutant embryos. All embryos were immuno-stained with mAb BP104, which recognizes an epitope on Nrg¹⁸⁰. HRP-conjugated secondary antibody and bright field illumination was used in (a, b, e, f) and Alexa488-conjugated secondary antibody and confocal microscopy in (c, d). (a, b) Dorsal views of filleted stage 16 embryos. (a) In the wild-type embryo, Nrg¹⁸⁰ is expressed by many central neurons, as well as in sensory neuron cell bodies (arrowhead shows lateral cluster) and their axons. Inset shows a higher magnification view of the area in the rectangle. (b) In an nrg¹⁴/Y;P0163-GAL4/UAS-nrg¹⁸ embryo, Nrg¹⁸⁰ is expressed in sensory neurons (arrowhead shows lateral cluster) and their axons, but not in central neurons. Stained structures in the CNS are sensory axons, shown at higher magnification in the inset (arrow). Note the lack of staining of cell bodies of neurons in the CNS. (c, d) Lateral view of PNS in two adjacent hemisegments in wild-type (c) and P0163-GAL4/UAS-nrg¹⁸ (d) stage 17 embryos. The same confocal microscope settings were used when imaging both embryos. The stronger staining in the embryo in (d) shows that the P0163-GAL4 driver was effective in driving elevated levels of Nrg¹⁸⁰ expression in sensory neurons. (e, f) Lateral view of stage 16 wild-type (e) and nrg¹⁴/Y mutant (f) embryos. In contrast to the positive staining of sensory axons (arrow) and the CNS (arrowhead) in the wild-type embryo, no staining is evident in these structures in the mutant embryo. Weak staining of the lumen of the dorsal trunk of the trachea (arrow), likely to be non-specific, is evident.