|Feature type||allele||Associated gene||Dmel\Dap160|
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|Nature of the Allele|
|Mutations Mapped to the Genome|
|Associated Sequence Data|
|Nature of the lesion|
|Phenotype Manifest In|
Dap160[EMS1]/Dap160[Δ2] third instar larvae have supernumerary boutons at the neuromuscular junctions of muscles 6/7 and 4 compared to controls.
The levels of membrane uptake (dye internalisation) in Dap160[Δ1]/Dap160[Δ2] mutant synaptic boutons in response to nerve stimulation is significantly reduced compared to controls. Increased uptake is seen when these flies are treated with chlorpromazine.
Homozygotes die as third instar larvae. Neuromuscular junction (NMJ) morphology is abnormal in Dap160Δ1/Dap160Δ2 third instar larvae; boutons are irregularly spaced and large boutons are surrounded by smaller satellite boutons. Bouton number normalised to muscle area is significantly increased in Dap160Δ1/Dap160Δ2 larvae (3.5 +/- 0.07 μm-2) compared to controls (1.7 +/- 0.07 μm-2). In addition, the boutons show more frequent branching than controls; the larval NMJ has 26.2 +/- 2.1 branch points per synapse in Dap160Δ1/Dap160Δ2 animals compared to 5.1 +/- 0.3 branch points per synapse for controls. In 5mM Ca2+ at 22oC, the amplitude of the excitatory junctional potential (EJP) at the neuromuscular junction (NMJ) in Dap160Δ1/Dap160Δ2 third instar larvae is not different from that of controls. The EJP amplitude at the NMJ of Dap160Δ1/Dap160Δ2 third instar larvae is normal in 5mM Ca2+ at 34oC. In 0.5 mM Ca2+, the EJP amplitude at the NMJ of Dap160Δ1/Dap160Δ2 third instar larvae is normal at 22oC, and is slightly reduced compared to controls at 34oC. In 0.5mM Ca2+, the frequency of miniature EJPs (mEJPs) at the NMJ is increased more than 2 fold in Dap160Δ1/Dap160Δ2 larvae compared to controls at 22oC. mEJPs with an unusually large amplitude are seen at both 22oC and 34oC. Dap160Δ1/Dap160Δ2 larvae show a mild defect in endocytosis at 22oC (assayed by dye uptake in third instar fillet preparations), which is exacerbated at 36oC. Dap160Δ1/Dap160Δ2 larvae show a stimulation-dependent decrease in EJP amplitude when stimulated at 10Hz. This decrease is more severe at 34oC than at 22oC. Ultrastructural analysis of the NMJ shows that the number of vesicles is reduced to about 60% of controls in Dap160Δ1/Dap160Δ2 larvae at 22oC without stimulation. The number of vesicles is further reduced to about 23% of controls upon stimulation in 60mM K+ at 34oC. The number of active zones is not reduced in the mutant larvae compared to controls, but there is a reduction in the number of vesicles at the active zones in mutant larvae at 22oC without stimulation and a further decrease upon stimulation with 60mM K+ at 34oC. There are an increased number of vesicles with large diameter in the mutant synapses. Endocytic intermediates, mostly consisting of collared pits and Ω structures are seen in the mutants (these structures are rarely seen in controls). The collared pits are seen at both the active zones and in periactive zones in the mutant larvae.
|Phenotype Manifest In|
|Complementation & Rescue Data|
|Stocks ( 1 )|
|Notes on Origin|
|External Crossreferences & Linkouts|
|Synonyms & Secondary IDs ( 2 )|
|Secondary FlyBase IDs|
|References ( 4 )|