Small deletion near the end of exon 6, resulting in a premature stop codon and deletion of approximately the final 25 amino acid residues of cpx.
Homozygous adult escapers are uncoordinated and ataxic.
Mutants show an increase in the frequency of spontaneous release at the third larval instar neuromuscular junction compared to controls. EPSC amplitude is reduced compared to wild type. Synaptic depression during short and long stimulation trains is different from wild type.