Picture from Zallen JA et al. (1998) Cell "The conserved immunoglobulin superfamily member SAX-3/Robo directs multiple ...."

Figure 4. Expression of sax-3::GFP. (A) Comma stage embryo. The anterior cells that express sax-3::GFP include developing neurons and epidermal cells. The ventral cells in the midbody are the ventral motor neuron precursors. Much weaker expression is observed in the lateral epidermal cells.(B) L1 stage larva. Expression is high in head motor neurons and interneurons (arrow). Muscles of the head and ventral body also express the transgene (arrowheads). Epidermal expression is absent by this time. No expression is observed in the immature HSN motor neurons.(C) L2 stage larva. The HSN motor neuron is extending a growth cone toward the ventral midline and expresses sax-3::GFP at high levels. Arrowhead denotes muscle expression.(D) L3 stage larva. The HSN axon has reached the ventral midline, but is not yet extending along the longitudinal bundles (arrow). The ventral muscles also express sax-3::GFP (arrowhead).(C) is a confocal image obtained by Tim Yu; all other images are taken using conventional fluorescence microscopy. Anterior is at left and dorsal is up in all panels. Scale bars = 10 μm.