Compared with wild-type, Df(1)446-20 mutants display increased spontaneous miniature excitatory junction potential (mini EJP) frequencies at larval neuromuscular junctions. Evoked EJPs in Df(1)446-20 larvae show a gradual decline in evoked EJP amplitude during the 10 Hz stimulation, while EJPs in wild-type larvae decline slightly less throughout the repetitive stimulation.

Df(1)446-20 mutant synapses show a significant reduction (about 40%) in fluorescent endocytic tracer uptake, indicating that there is a defect in endocytosis at the NMJ.

Df(1)446-20 mutant larvae have locomotion defects. The mutants exhibit significantly shorter average locomotor path lengths compared with those of wild-type larvae.

Df(1)446-20 mutant embryos display an abnormal complement of eve-positive neural precursors and neurons at stage 11/12. Many hemisegments exhibit a variety of phenotypes including the loss of GMC4.2a, extra RP2/sib neurons, disorganised eve+ clusters, and extra aCC/pCC cells. Later in development at stages 14-15 loss of eve+ RP2s is observed in a small, but significant, percentage of hemisegments.

Df(1)446-20 mutant stage 17 embryos show mild to severe CNS axon guidance defects; defects range from mild phenotypes such as irregularly spaced axon tracts in commissures and wavy, thinning longitudinal connectives, to more severe phenotypes such as fused commissures and disorganized CNS tracts. Disruption is also seen to the Fas2-positive longitudinal connectives with phenotypes varying in severity ranging from loose and defasiculated connectives to ectopic midline crossing.

Chordotonal neurons (lch5) in the developing PNS are abnormal in many Df(1)446-20 mutant stage 17 embryos. Defects include a decreased number of sensory neurons, fused and abnormally shaped neurons, organisational and positional defects and thin axon bundles. No detectable difference is seen in the axon projections in the l, v and v' neuron clusters.

Homozygous adults accumulate abnormal storage material in their brains; these deposits are fairly homogeneous in structure, being predominantly spherical in shape and composed of tens to hundreds of concentric layers of material, each layer being 4-12nm in thickness and often surrounding a granular core from which the laminar material seems to emanate. The laminar deposits are found in the cytoplasm, typically near the nucleus, in approximately 90% of the cell bodies in any given field of view. No deposits are detected in sections from neuropil regions of the brain. The deposits grow in size through the accumulation of additional layers of storage material as the flies age. Deposits in the brains of males are consistently larger and more aggregated than those in females, and those in males contain more prominent gaps and spaces between the layers of material. Laminar deposits are also found in the thoracic ganglion in adults. Laminar deposits are also found in the third-instar larval brain and in the adult gut epithelium, although these deposits are smaller, more diffuse and much less abundant than those seen in the adult central nervous system. No abnormal deposits are detected in the brains of heterozygous adults.

Homozygous flies accumulate autofluorescent inclusions in the brain; at 36 hours after pupation, autofluorescent inclusions are detected, but there is no difference between Df(1)446-20 and wild-type flies, however, by 72 hours after pupation, the autofluorescent inclusions in homozygous brains are significantly larger and significantly more abundant than the autofluorescent material (lipofuscin) found in wild-type brains, and this difference persists into adulthood.

The median lifespan of Df(1)446-20 hemizygotes is reduced 32% compared to controls.

Homozygous flies are viable and fertile.