Figure 4. The electrophysiological response at the muscle 6/7 NMJ is controlled by JhI-21.

(a) Schematic representation of the JhI-21 genomic locus. Exons are indicated by boxes, translated exons of the JhI-21 gene by black boxes, 5´and 3´untranslated regions of the JhI-21 gene as gray boxes. Triangles represent the inserting region of P-elements used to generate hypo-(stripped triangle) or hypermorph (grey triangle) JhI-21 alleles. (b) Representative traces for two-electrode voltage clamp experiments from the larval muscle 6 (LIII). As wildtype we used w¹¹¹⁸ (control 1) and a clean excision of P(KG00977) (control 2). (c) Relative cumulative frequency histogram of sEJC (“mini”) amplitudes from different genotypes in third-instar Drosophila larvae. Rightward shift (JhI-21 KG and JhI-21 KG/Df1, blue) indicates increase in the abundance of current-conducting postsynaptic receptors, i.e larger synaptic currents. Note the shift to the left (i.e. decreased receptor number) in JhI-21 overexpression mutants (gray) N = 6-10 animals, 800-3.400 events measured. Kolmogorov-Smirnov test was used to compare the cumulative distributions two by two (*P < 0.05; **P < 0.01). (d) Negative correlation between the JhI-21 mRNA levels and the number of sEJC amplitudes at the NMJ. (e) Motor neurons were stained using anti-HRP and confocal images were taken at the 6/7 NMJ. Neither JhI-21 KG nor JhI-21 KG/Df1 showed alterations of synaptic morphology in terms of NMJ branches, bouton number, or bouton area using a Kruskal-Wallis test. Error bars represent SEM in d and e.