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. 2019 Jun 21;8:e48594. doi: 10.7554/eLife.48594

Figure 2. Axon fasciculation requires full-length PlexB but not its cytoplasmic motifs individually.

Figure 2.

(A) In a wild-type fly brain at 24hAPF, ORN axons fasciculate into two bundles (left panel; white arrowheads) surrounding the antennal lobe without innervating it (left panel; empty white arrowhead). Loss of PlexB (plexB–/–) causes defasciculation of ORN axons with differing severity (middle and right panels; red arrowheads). In the severe cases, axon bundles are completely missing (right panel; empty blue arrowheads). ORN axons were labeled by pan-ORN Peb-GAL4 (Sweeney et al., 2007) driven mtdTomato expression. (B) Quantification of fasciculation defects by binning antennal lobes into three categories – no, mild, and severe defasciculation. Expressing wild-type PlexB in ORNs significantly but not completely restores ORN axon fasciculation in plexB mutant flies. ‘Rescue’ hereafter denotes ORN-specific expression of PlexB variants in plexB–/– flies. (C–K) Quantification of fasciculation defects in ORN-specific rescue experiments with respective PlexB variants. Sample sizes are noted in parentheses. Significance of the contingency tables in Figure 2B–K was determined by Fisher’s exact test. ns, not significant; **p<0.01; ***p<0.001; ****p<0.0001. Images are shown as maximum z-projections of confocal stacks. Scale bars, 10 µm. Axes, D (dorsal), L (lateral).