Neuromuscular junction (NMJ) synapses appear relatively normal ultrastructurally in homozygous embryos, except that pre- and postsynaptic densities are incompletely apposed. The number of synaptic vesicles, dense core vesicles, active zone diameter and postsynaptic density diameter are all statistically indistinguishable from wild type. NMJ size and the number of active zones/NMJ are significantly reduced in the homozygous embryos compared to wild type. The amplitude of the evoked excitatory junction current (EJC) is reduced in homozygous embryonic NMJs compared to wild type, while the frequency of spontaneous EJCs is unaffected. There is no change in the amplitude of glutamate-gated currents at the NMJ in these embryos.