SmoxMB388 mutant larvae display enlarged anal pads. Central nervous system hypotrophy is seen at the late third instar larval stage.
Homozygous clones in the wing do not result in a mutant phenotype.
Late third instar SmoxMB388 larvae show photoreceptor axon targeting defects. The number of glia in the medulla and lamina is reduced.
The number of cells in M phase in the developing optic lobes is significantly reduced in SmoxMB388 third instar larvae compared to controls. The size of the outer proliferation center and inner proliferation center zones is reduced in these larvae, although they still contain many cells in S phase. The ratio of M-phase cells to S-phase cells is thus reduced in the mutant optic lobes compared to wild type.
SmoxMB388 embryos show axon guidance defects; 21% of hemisegments have ISNb pathfinding defects and 7% show loss of lateral or dorsal branches.
Photoreceptor R1-R6 axons project into the brain and form a relatively normal but very reduced lamina in SmoxMB388 mutant larvae, but R7 and R8 axons never form a normal lattice network and their growth cones are collapsed. The medulla neuropil is significantly reduced in size and altered in morphology in the mutant larvae.
When single cell mutant clones in adult γ neurons, abnormal projection patterns are seen. Mutant neurons possess two major axonal branches that project perpendicularly away from each other, as in larval γ projections. Wild-type patterns of dendrites and axons are seen in mutant γ neurons before puparium formation. However pruning of larval dendrites and axons does not happen to mutant neurons during early metamorphosis, persisting to adult stages.