Figure 4. Trn overexpression in muscle subsets causes mistargeting.
(A) Classification of observed mistargeting phenotypes. Green lines indicate normally patterned NMJs on muscles 6,7, 12, and 13. The TN is indicated at the left. Red lines indicate ectopic (mistargeted) NMJs. (B–G) Confocal z-stack images of the VLM regions of 3rd instar F1 larvae stained with 1D4 (anti-FasII; green). Muscles (gray) were visualized by UAS-GFP driven by 24B-GAL4 (B,C) or by phalloidin staining (D–G). (B) Control (UAS-GFP, 24B-GAL4 × w). (C) Overexpression of intact Trn (in GS10885 × UAS-GFP, 24B-GAL4). Arrow in (C), ectopic NMJ wrapping over the dorsal edge of m12 (Type 3). Arrowheads in (C), ectopic NMJ on m12/13, presumably split off from the normal NMJ. (D–E) Trn overexpression on muscles 13 and 6 (in GS10885 × H94-GAL4). Arrow in (D), ectopic innervation of m6 (Type 7); arrow in (E) indicates the absence of innervation on m13 (only an axon traversing m13 is observed; Type 8). (F–G) Trn overexpression on m12 only (in GS10885 × 5053A-GAL4). Arrow in (F), a branch of the m13 NMJ extends dorsally but there is no innervation of m12 (Type 2); arrow in (G), the NMJ on m12 emerges from under m13, and there is no axon crossing over m13 (Type 5). (H) Bar graph of total phenotypic percentages. Numbers of A2 hemisegments examined indicated on bars. (I) Bar graph showing the distribution of phenotypes among the categories illustrated in (A). Bar in (B), 50µm: applies also to (C–G).