Fos and Jun are expressed in motor neurons marked by the C380 enhancer. In third-instar larval ventral ganglia, C380 enhancer-driven nuclear GFP (A) marks the dorso-medial cells labelled with the neuronal marker Elav (B and C) and (D) by retrograde fills of the motor nerve (cells circled by a yellow line; cells with a green boundary represent the complementary neurons on the adjoining hemisegment). An arrowhead marks RP2 and an arrow marks aCC in 1C. An asterisk marks a dorsal medial neuron not labelled by C380. Both Fos (F) and Jun (I) are expressed strongly in medial motor neurons marked by the C380 enhancer (E and H). Figure 1G and 1J are merged images of the above showing Fos and Jun expression in identified C380 positive motor neurons. Fos and Jun are also expressed at lower levels in other neurons and non-neuronal cells including CNS glia (not shown). 1K shows a stage 15 embryo expressing C380-Nls-GFP (green) counterstained with anti-elav (red) to mark all differentiated neurons. GFP expression is only seen in PNS neurons (arrowhead) and in salivary gland (asterisk). C380 driven GFP can be detected at high levels at motor synapses in the third instar larva such as that on muscles 6 and 7 (L). The synapse is counterstained with anti-synaptotagmin to mark synaptic boutons (arrowhead). Figure 1M shows a third instar ventral ganglion stained for nuclear lacZ. This expression pattern closely mimics that of C380-GAL4. In this animal, lacZ is expressed from an actin promoter only in cells in which "flip-out" of a stuffer DNA has occurred due to C380-GAL4 driven UAS-FLP. Figure 1N shows C380 driven membrane bound cd8-GFP expression in the dorsal medial region of a third instar ventral ganglion. 1O shows n-lacZ in the same animal and 1P is a merged image showing that n-lacZ is expressed only in the motor neurons that are also positive for C380 expression at this developmental stage. The specificity of the Fos antibodies is shown by increased immunoreactivity in motor neurons when AP1 is expressed under control of the C380 enhancer (Q and R). The dashed yellow lines in all cases approximately mark the midline.