Erect wing restricts synaptic growth at third instar neuromuscular junctions. (a) Schematic of the eFeG construct used for clonal analysis of ewgl1, an embryonic lethal allele. (b,c) FLP/FRT mediated recombination in photoreceptor neurons in third instar larval eye disc. Note that CD8::GFP is expressed (c) in the ewgl1clone (b). The scale bar in (c) is 25 μm. (d-i) NMJs of control and ewgl1clones in third instar larvae. Clones of controls (d-f, in ewgl1eFeG/+; hs-flp/+ UAS-CD8::GFP/+ females, rec. control in (j)) and of ewgl1(g-i, in ewgl1eFeG/Y; hs-flp/+ UAS-CD8::GFP/+ males) were stained with anti-SYT or with anti-CD8 antibodies to visualize synaptic growth defects of type 1b boutons at muscle 13. The scale bar in (i) is 20 μm. (j) Quantification of synaptic growth defects in ewgl1mutant neurons. Shown are means of bouton numbers (type 1b at muscle 13) with standard errors (n = 21-35). Rec. control refers to clones made in the presence of one copy of ewg+ as in ewgl1eFeG/+; hs-flp/+ UAS-CD8::GFP/+ females. Tetanus toxin was expressed from a UAS transgene in clones by the recombined eFeG construct. Statistical significance of differences from comparisons with wild type is shown on top of bars (***p < 0.0001, **p < 0.001, n.s. for non significant). Other relevant comparisons are marked by horizontal bars with the statistical significance indicated on the side. (k-n) Distribution of synaptic markers is normal at ewgl1NMJs. Active zones were stained with anti-Nc82 at wild type (k) or ewgl1NMJs (m) and periactive zones were stained with anti-Highwire at wild type (l) or ewgl1NMJs (n). The scale bar in (n) is 1 μm.