In Dhc64C4-19/Dhc64C6-10 mutant third instar larvae, amplitudes of evoked excitatory junctional potentials (EJPs) in abdominal muscles (a measure of the extent of neurotransmitter release) are indistinguishable from wild-type for at least 30 minutes of low-frequency electrical stimulation (0.5 Hz) of motor neurons. The amplitude and frequency of spontaneous miniature EJPs (mEJPs) in the mutants are not significantly different from that of wild-type. In contrast, Dhc64C4-19/Dhc64C6-10 mutants are unable to sustain normal levels of neurotransmission during high-frequency electrical stimulation. EJP amplitudes in the mutants declined abnormally rapidly within five minutes of stimulation at 10 Hz. There is an upturn in EJP amplitudes after switching from 10 to 0.5 Hz stimulation in the mutants. The EJP response does not reach wild-type levels in the mutants even one hundred seconds after switching from high- to low-frequency stimulation.
The total amount of the lipophilic dye FM 1-43 taken up into boutons during 10 Hz stimulation is significantly reduced in BicDr5/Df(2L)TW119 mutants, compared with controls. Potassium-induced unloading of FM1-43 (pre-loaded into an internalised vesicle population during stimulation) is defective in Dhc64C4-19/Dhc64C6-10 mutants.
Dhc64C6-10/Dhc64C4-19 hypomorphic heterozygous mutants appear normal and display neuromuscular junctions indistinguishable from wild-type. At 7 and 9 hours after puparium formation there is no obvious change in synaptic vesicle distribution (compared to a redistribution in wild-type). These mutants also show considerably larger synaptic areas compared to wild-type.
No crawling defects are detected in heterozygous Dhc64C6-10 third instar larvae and adult eyes appear normal. Vesicle movement in segmental axons does not appear to be disrupted.
Neuroblasts in the brains of homozygous larvae have an altered mitotic distribution (increased metaphase and decreased prometaphase) and abnormal mitotic figures are seen. BrdU incorporation is reduced compared to controls and disorganisation of the cycling cells is seen. Neuronal apoptosis is increased 6 times compared to wild type.
Egg chambers in homozygous female germline clones consist of 16 nurse cells (the oocyte does not differentiate).
The retrograde flux of mitochondria in the motor axons of Dhc64C6-10/Dhc64C4-19 larvae is reduced more than sixfold compared to wild-type larvae. Dhc64C6-10/Dhc64C4-19 nerves show axonal swellings although these do not appear to be the cause of the mitochondrial transport problems.
In embryos laid by Dhc64C8-1/Dhc64C6-10 females the force (applied with optical tweezers) required to stall plus end travel of lipid droplets is significantly less than for wild-type embryos. The velocity of plus end droplet travel is significantly reduced in these mutants, especially over long runs (500-1000 nm), as is the mean plus end travel distance. In addition, the frequency of pauses during plus end travel is increased. In embryos laid by Dhc64C6-10/+ females the force (applied with optical tweezers) required to stall plus end travel of lipid droplets is not significantly different than for wild-type embryos. The ratio of short slow transport to long fast transport states for lipid droplets in these embryos is higher (plus end transport 4.44+/-2.09 ; minus end transport 2.42 +/- 0.69) than wild-type (plus end transport 2.15+/-0.59 ; minus end transport 1.05 +/- 0.22).
Dhc64C6-10/Df(3L)10H larval neuroblasts show a variety of mitotic defects. The ratio of metaphase/anaphase figures is 9.2 in the mutant animals compared to 2.9 in the wild type. The mitotic index is 1.6 compared to 1.0 in the wild type. There is a higher frequency of overcondensed metaphases than in the wild type and 7% polyploid metaphases. A high frequency of abnormal anaphases are seen.
Dhc64C8-1/Dhc64C6-10 animals survive to give fertile adults. Embryos laid by Dhc64C8-1/Dhc64C6-10 females develop seemingly normally through cellularisation and early gastrulation. However, lipid droplets fail to redistribute from the centre towards the periphery of these embryos during early cycle 14, in contrast to wild type. This results in embryos that are abnormally transparent from gastrulation onward.
Dhc64C6-10/Df(3L)10H hemizygous larvae show lethality during late larval and pupal stages. Dhc64C6-10/Dhc64Cek1 larvae show earlier lethality with a greater proportion of deaths occurring during the third larval instar stage. Dhc64C6-10/Df(3L)10H hemizygous larvae show posterior paralysis phenotypes. The penetrance of this phenotype is 100%. The distribution of microtubules in segmental nerves appears normal. Axon swellings filled with retrograde transport organelles, including lysosomal and multivesicular bodies, are seen in the segmental nerves. The axonal swellings also contain mitochondria, many small vesicles and smooth tubular membranes.
Dhc64C6-10/Df(3L)10H hemizygous larval neuroblasts frequently show a reduced affinity of centrosomes for spindle poles. Spindle microtubule bundles are often disrupted and curved.
Weak allele. 55% of lethality acts during larval stages and 42% during pupal phase. Low levels (3-12%) of embryonic lethality are observed.
Dhc64C3-2/Dhc64C6-10 flies show disruptions in the shape, size and organisation of the ommatidia.