There is a significant increase in the length of each pre-synaptic density at larval neuromuscular junctions (NMJs) in dlg17
homozygotes compared to wild-type. However, the thickness of the sub-synaptic reticulum at these NMJs is significantly decreased.
Electrophysiological readings from the neuromuscular junctions of dlg17
homozygotes show significantly increased mini excitatory junction potential amplitude and significantly decreased evoked excitatory junction potential amplitude compared to controls. Together these indicate decreased quantal content.
Homozygotes show a severe decrease in the number of boutons at the neuromuscular junction compared to controls. The subsynaptic reticulum is less developed in the mutant boutons than in control boutons.
The amplitude of the miniature and evoked excitatory junctional currents are reduced compared to controls in mutant animals. The frequency of the miniature excitatory junctional current and the quantal content are not significantly altered.
Mutants show defects at the larval neuromuscular junction (NMJ); boutons are enlarged and abnormal NMJ arbors are seen. There is a reduction in the subsynaptic reticulum and an increase in the number of active zones.
Follicle cells do not have an invasive phenotype in females with homozygous dlg17
clones in the germ cells and follicle cells.
Type Ib boutons at the neuromuscular junction appear bloated.
The subsynaptic reticulum at type I boutons is greatly reduced in hemizygous flies, such that it fails to surround the type I boutons or forms very few folds at the junctional region. There is an increase in the number of active zones within single type I boutons. The presynaptic terminal of type I boutons is larger in cross-sectional area in hemizygous flies compared to wild-type. The increased number of active zones is completely rescued if dlg1Scer\UAS.cBa
is targeted to the presynaptic cell or simultaneously to both pre- and postsynaptic cells using Scer\GAL4unspecified
. The presynaptic morphological phenotype is partially rescued if dlg1Scer\UAS.cBa
is targeted only to the postsynaptic cell using Scer\GAL4unspecified
Homozygous larval show overgrowth of the imaginal discs. Imaginal disc cells have apical junctions and exhibit normal apicobasal polarity.
Neoplastic imaginal disc overgrowth, affecting all discs. Discs implanted into wild type hosts for metamorphosis overgrow and do not differentiate. Mutant larvae grow at a normal rate until end of feeding period of last larval instar, when growth slows and then stops: they eventually reach double the weight of wild type pupariating larvae. Pupariation delay can be prevented by γ irradiation (destroying proliferating cells) shortly before hatching (Poodry and Woods, Wilhelm Roux's Arch 199:219--227 ). Ecdysteroid titer for all mutants fails to show peak that is associated with pupariation in the wild type. The ecdysteroid secretory activity of dlg1 and l(3)dco ring glands in vitro is 1/6 that of wild type. When overgrowth of the imaginal discs is prevented by γ irradiation the normal profile of ecdysteroid titers is restored, and ecdysteroid production from explanted ring glands is elevated.
Larval life prolonged by up to 14 days. Overgrown larvae show bloating and an increase in water content.
Clonal analysis shows small clones for dlg1 can produce cuticle demonstrating that surrounding wild type tissue can partially rescue the defect in differentiation.
Homozygotes fail to pupariate at 25oC and die as very bloated larvae with some partially tanned cuticle. The larval brain show extensive overgrowth of the cerebral hemispheres. Irradiation of larvae results in 100% rescue of the pupariation delay.
Hemizygous larvae have abnormal wing discs; the wing discs are smaller than normal and have an abnormal morphology up to the time of pupariation in normal larvae. Hemizygous larvae fail to pupariate at 25oC, and have an extended third larval instar period compared to wild-type that lasts up to about 15 days after egg laying (AEL). During this time the wing discs overgrow, and by 11 days AEL begin to fuse with the haltere and third leg discs. The optic lobes of the brain also become greatly enlarged, and fusion occurs between the first and second leg discs and the ventral ganglion. All the imaginal discs appear to be affected in a similar manner, but fusion only occurs between discs that are close together. The larvae take on a swollen, bloated appearance during the extended third larval instar period. About 15 days AEL they form a "pseudopupa" with some tanning of the larval cuticle.