|Feature type||allele||Associated gene||Dmel\Syt4|
|Allele class||amorphic allele - molecular evidence|
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|Nature of the Allele|
|Mutations Mapped to the Genome|
|Associated Sequence Data|
|Nature of the lesion|
|Phenotype Manifest In|
Syt4[BA1] mutants reduce synaptic growth at the neuromuscular junction with a 24% decrease in varicosity number compared to controls. Active zone number appears to parallel bouton number. Syt4[BA1]/Df(3R)rn mutants reduce synaptic growth at the neuromuscular junction with a 28% decrease in varicosity number compared to controls. Active zone number appears to parallel bouton number. Homozygous Syt4[BA1] mutants exhibit reduced spontaneous neurotransmitter release in the absence of nerve stimulation (at 0.5mM Ca[2+] concentration). These changes in evoked responses are not observed in 2.0mM extracellular Ca[2+] concentration, suggesting that alterations in release probability or vesicle pool size may compensate for the altered number of release sites. The fast component of synaptic depression release during initial stimulation is unchanged. However, a lower depletion of synaptic vesicles and a higher baseline-evoked response during steady-state stimulation is observed in Syt4[BA1] mutants. Syt4[BA1] mutants fail to show increased spontaneous release after stimulation. Althoygh control larvae show a 33% increase in bouton number when reared at 31[o]c compared with 25[o]C, Syt4[BA1] mutants display no statistically significant increase in bouton number at 31[o]C.
There are no statistical differences in evoked excitatory junctional potential amplitudes between Syt4[BA1] animals and controls, even at low 0.1 mM extracellular Ca[2+] concentrations. Also, the amount of facilitation at all interpulse intervals tested was statistically the same as controls, indicating paired-pulse facilitation is unaffected.
High-frequency-stimulation-induced miniature release (HFMR) is eliminated in the neuromuscular junctions of SytIVBA1 animals, in contrast to controls. The presynaptic morphology of motor terminals is abnormal at the mutant neuromuscular junction; the motor terminals fail to constrict into normal synaptic varicosities and maintain a flat, less varicose appearance.
|NOT Enhancer of|
|Phenotype Manifest In|
sei ; Syt4[BA1] double mutants exhibit no significant change in bouton number between 25[o]c and 31[o]C. Synaptic outgrowth induced by expression of Syt4[wt.Scer\UAS] under the control of Scer\GAL4[Mhc.PW] is dramatically reduced in a para[ts1] background when animals are reared at 31[o]C compared with 25[o]C.
Like Syt1[AD4]/Syt1[N13] mutants alone, Syt1[AD4]/Syt1[N13], Syt4[BA1] double mutants display robust asynchronous release. Paired-pulse facilitation remains intact in the double mutants, with enhanced facilitation as observed in Syt1[AD4]/Syt1[N13] mutants alone. Also similar to Syt1[AD4]/Syt1[N13] mutants alone, the release observed during paired-pulse stimulation in the double mutants remains asynchronous compared to wild type controls.
|Complementation & Rescue Data|
|Not rescued by|
|Stocks ( 0 )|
|Notes on Origin|
|External Crossreferences & Linkouts|
|Synonyms & Secondary IDs ( 3 )|
|Secondary FlyBase IDs|
|References ( 4 )|