Second/third instar larvae unc-13^EMS7.5/unc-13^P84200 that also express unc-13^{GoF.UAS.A.GFP} under the control of Scer\GAL4^RapGAP1-OK6 show neurotransmission defect at the muscle 6 NMJ: increased evoked release amplitude; increase in frequency but decrease in amplitude of spontaneous release events.

unc-13^EMS7.5/unc-13^P84200 transheterozygotes are nearly lethal, as they give rise to few larvae, which hardly move and only occasionally develop into weak adult flies.

The third instar larval neuromuscular junction of unc-13^P84200/unc-13^EMS7.5 transheterozygotes exhibit a significant decrease in active zone density (identified by Bruchpilot puncta), which are often larger and exhibit apparently larger T-bars and a decrease in the number of synaptic vesicles docked in close proximity to the T-bar center, as compared to controls; neurotransmission at these neuromuscular junctions exhibits a severe decrease in the amplitude and a significant increase in the rise time of evoked excitatory currents, and significant increases in the amplitude and the frequency, but not in the rise time or decay time, of miniature excitatory currents, as compared to controls.