Physiology and morphology defects at <i>neto-β</i> mutant NMJs.

<p>(A–F) Electrophysiological recordings of control (precise excision) and <i>neto-β</i> alleles of third instar animals. Representative traces of mEJPs and EJPs at 0.8 mM Ca²⁺ are shown in (A) and (D), respectively, and the results are summarized in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005191#pgen.1005191.s008" target="_blank">S1 Table</a>. The number of NMJs examined is indicated in each bar. The mEJPs amplitude (B) and frequency (C) were reduced for both <i>neto-β</i> alleles. The EJPs amplitude was reduced in <i>neto</i>^{<i>βshort</i>} compared to controls, but was normal at <i>neto</i>^{<i>βnull</i>} NMJs (E). Both alleles had increased quantal content, indicating a presynaptic compensatory response (F). The muscle resting potential and the input resistance were not affected. (G-H) Representative confocal images at NMJ4 and NMJ6/7 (segment A3) in third instar larvae of indicated genotypes labeled with HRP. The <i>neto-β</i> mutant NMJs have significantly fewer and larger boutons relative to the muscle area (quantified in I-J). In particular, the volume of distal boutons increases 2.4 and respectively 2.6 fold at <i>neto</i>^{<i>βshort</i>} and <i>neto</i>^{<i>βnull</i>} NMJs. Error bars indicate SEM. ***; p<0.001, **; p<0.005, *; p<0.05, ns; p>0.05. Scale bars: 20 μm, 2 μm in details.