Fig. 3. Amphiphysin is required for postsynaptic protein localization and synaptic function at larval type I neuromuscular junctions. (A) Miniature excitatory junctional potentials (mEJP) recordings reveal there is a small but significant increase in quantal size in amph mutants. Left panels show representative traces of mEJPs from amph²⁶ mutant and wild-type (amph⁺¹) flies. Histograms and comparative cumulative plots are shown on the right. The average mEJP for the amph⁺¹/amph⁺¹ is 0.81±0.01 mV (n=2804) and for amph²⁶/amph²⁶ is 0.94±0.02 mV (n=2148) (P<0.05). (B) There is no change in the amplitude of the elicited response in amph mutants. Elicited response is measured as excitatory junctional potentials (EJPs) for amph²⁶ mutants and wild type (amph⁺¹). Representative EJP tracings from amph²⁶/amph²⁶ and amph⁺¹/amph⁺¹ larva (top). Histograms representing the average amplitude for each genotype (bottom): amph²⁶/amph²⁶ 35.5±1.29 mV (n=16) and amph⁺¹/amph⁺¹ 34.9±1.22 mV (n=15) P>0.1. (C) Immunohistochemical examination of the third instar NMJ of wild type (top) and amph²⁶ mutant (bottom) larva. The NMJs of muscles 6 and 7 of abdominal segment 2 are shown. The localization of Dlg, Lgl and GluRIIB are shown. In amph mutants, Lgl is absent from the synapse but still maintained in the M band of the muscle. GluRIIB protein localization at the NMJ is identical in wild type and amph²⁶ mutants. (D) Immunohistochemical examination of the third instar larval NMJ in wild type (top) and amph²⁶ mutants (bottom). The NMJs of muscle 6 and 7 of abdominal segment 2 are shown. The boxed areas represent the magnified views of the accompanying panels. In amph mutants, both Scrib and Dlg still show localization to the synapse but there is protein delocalized throughout the muscle.