Overexpression of SytIVScer\UAS.cLa, under the regulation of both Scer\GAL4elav-C155 and Scer\GAL4elav.PLu does not rescue the sytAD4/sytN13 phenotype. However, this overexpression does result in a 96% reduction in the expected Mendelian ratios. Overexpression of SytIVScer\UAS.cLa, under the regulation of Scer\GAL4elav-C155, in a sytAD4/sytN13 null mutant background has no effect on the synaptic transmission defects. Only slow release reflecting the asynchronous component of fusion is observed with the evoked EJP unchanged from the null mutant alone.
The lack of high-frequency-stimulation-induced miniature release (HFMR) seen in Df(3R)rn16 animals is rescued by expression of SytIVScer\UAS.cLa under the control of Scer\GAL4Mhc.PW (postsynaptic expression) but not by expression of SytIVScer\UAS.cLa under the control of Scer\GAL4elav-C155 (presynaptic expression).