robo31/robo31 MARCM clones (in Scer\GAL4fru-NP0021 neurons) develop a male-specific ipsilateral ectopic neurite in female brains at a low frequency (no effect in controls or mutant male clones).
The adult sLNv neurons of robo31 homozygotes exhibit significantly longer axonal projections compared to controls.
Examination of the optic lobes of homozygous robo31 mutants does not reveal any defects.
In robo31 mutants, the intermediate Fas2-positive tract shifts towards the midline and joins the medial pathway. Thus, only two distinct Fas2-positive bundles (medial and lateral) are detectable in these embryos. The Scer\GAL4ap-md544-expressing axons are found in their wild-type position directly adjacent to the medial Fas2-tract.
Homozygous embryos show a highly penetrant medial shift of the intermediate Fas2-positive longitudinal fascicle.
46% of homozygous embryos hatch into first instar larvae, 29.5% of the embryos reach the pupal stage and 27.5% of the embryos eclose into adults.
Homozygotes have have defects in the ellipsoid body.
Homozygotes show defects in the mushroom body; 100% have the dorsal lobes close to the midline, 73% show crosswise projection of the γ fiber and 48% lack the median projection.
robo31/robo31 DM2 glomerulus innervating neurons, produced by mitotic recombination in a robo31/+ background, often project to ectopic sites in the antennal lobes, rather than to the DM2 glomerulus. The erroneously placed terminals form large, irregular "glomerular-like" structures that do not correspond in shape or position to those previously identified in wild-type animals.
In embryonic stage 16 robo31 mutants, the medial and intermediate axonal fascicles fuse, with some longitudinal glia lining up over the fused fascicles, whereas some remain laterally together with remaining lateral axons (100% penetrance).
Homozygous larvae have no detectable defect in distal cell neuron positioning in the visual system.
Homozygous embryos do not show defects in lch5 or dorsal cluster sensory axon growth.
The ch neuron projections in robo31/+ embryos are normal. The ch neuron projections in homozygous robo31 embryos are shifted to the medial, rather than the intermediate longitudinal fascicle, as are most of the Fas2 fascicles. The dbd neuron projection is unchanged. When robo3Scer\UAS.cSa is expressed in the PNS by Scer\GAL412.1 in a robo31 mutant the medial fascicle is increased at the expense of the intermediate fascicle, as for robo31, but the ch neuron projections remain with the intermediate longitudinal fascicle.
Axonal projections in the visual system are not disrupted in mutants. Homozygous embryos show defects in the arrangement of Fas2-expressing fascicles. The intermediate fascicle shifts medially to fuse with the medial fascicle in 98.8% of embryos. 25.2% of embryos show breaks in the lateral fascicle. The axons of the "Sema2b" neurons (which express the marker Btau\MAPTSema-2b.T:Hsap\MYC), but not the cell bodies, are shifted much closer to the midline in mutant embryos.