Vha100-11 homozygous whole-eye clones, induced in the third instar larva, lose on-off retinal transients in response to short light pulses in the adult.
Vha100-12 in combination with Vha100-12, Vha100-13, Vha100-14, Vha100-15 or Df(3R)3450 develop to late embryonic stages, but fail to hatch. The same phenotype is seen when these embryos are born to mothers with a Vha100-11 homozygous germ-line.
Flies in which the retina is homozygous for Vha100-11 (made using the 'ey-flp' system described in FBrf0125463) consistently fail to walk toward light in a phototaxis assay. Electro-retinograms from these animals display normal depolarization in response to light stimuli, but exhibit a complete loss of 'on' and 'off' transients, indicative of a failure to evoke a postsynaptic response.
When eye photoreceptor cells are selectively made homozygous for Vha100-11 (using Scer\FLP1ey.3.5.hs; Scer\FRT Vha100-11/Scer\FRT 'cell-lethal'), their projections into the brain appear normal. Despite some subtle defects in the lamina, the cartridges of the lamina also appear normally organised. However, mutant terminals show an approximately 2.5 fold (p<0.0001) increase in vesicle density compared to wild-type. In addition the number of capitate projections (dynamically active invaginations of the surrounding epithelial glia associated with vesicle endocytosis) is reduced (p<0.001) and some mutant terminals appear enlarged. The numbers of active zones and mitochondria per terminal are unaltered in mutant photoreceptor cells.
The frequency, but not the amplitude, of mini excitatory postsynaptic currents is significantly reduced (p<0.05) at the neuromuscular junctions of Vha100-11/Df(3R)3450 embryos. However, excitatory postsynaptic currents induced by stimulation of the motor nerve supplying muscle 6 in these embryos have significantly lower amplitudes and higher failure rate than in wild-type. As in wild-type, postsynaptic currents are induced in response to application of a hypertonic solution at the neuromuscular junction.
Assays of dye-uptake (FM1-43) into boutons at neuromuscular junctions indicate a significant reduction in vesicle cycling at unstimulated junctions of Vha100-11/Df(3R)3450 embryos compared to wild-type.