Abp1 deficiency causes defects in NMJ development.

<p>(<b>A</b>) Examples of NMJs at muscles 6/7 of abdominal segment A2 from <i>wt</i>, <i>abp1</i>^KO/Df(3 L) and hemizygous <i>abp1^WH-rev</i> larvae, respectively, stained for pre- and postsynaptic markers HRP (green) and Dlg (red). Note that the NMJs of <i>abp1</i>^KO/Df(3 L) flies (middle) appear condensed and less arborized and contain fewer synaptic boutons type Ib when compared to <i>wt</i> and to revertants generated to restore <i>abp1</i> expression by precise excision to demonstrate the specificity of <i>abp1</i> knock-out phenotypes. Bars, 20 µm. (<b>B,C</b>) Quantification of type Ib bouton numbers (<b>B</b>) and terminal axonal branch points (<b>C</b>). The significant reduction in the number of boutons and branch points observed in all <i>abp1</i>-mutant allelic combinations are restored in the revertant <i>abp1^WH-rev</i>. (<b>D</b>) HRP and anti-Dlg-stained NMJs of <i>abp1</i>-deficient larvae with postsynaptic Abp1 re-expression (C57<i>-Gal4</i>+Abp1+<i>abp1</i>^KO/Df(3 L)) and of larvae with a presynaptic rescue of Abp1 functions (OK371-<i>Gal4</i>+Abp1+<i>abp1</i>^KO/Df(3 L)). Bar, 20 µm. (<b>E,F</b>) Quantitative analyses of type Ib boutons and of terminal axonal branch points show that only presynaptic expression of Abp1 rescues bouton number whereas the number of terminal axonal branch points can be rescued by both pre- and postsynaptic expression of Abp1. Data represent mean±SEM. n = 19–42 NMJs/genotype. * = p<0.05, ** = p<0.01 and *** = p<0.001. One way ANOVA post Tukey.