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. 2019 Feb 4;8:e42692. doi: 10.7554/eLife.42692

Figure 7. Dpr10 Expression is gradually restricted to distal fibers of the Ti-ltm 30 to 45 hr APF.

(A–B) Dpr10 protein expression (grey) in the developing Ti-ltm and proximal tadm, labeled by Mef2 (magenta) along with αTi-ltm and αTi-tadm axons labeled by DIP-α-T2AQF > 10XQUAS-6XGFP (green) at 25 hr (A) and 45 hr (B) APF. Left: GFP, Mef2 and Dpr10; middle: GFP and Mef2; right: Dpr10. (A’,B’) show magnified single slice images of the dashed boxes indicated in A,B. While Dpr10 is widely expressed in the entire Ti-ltm at 25 hr APF (A) (dashed boundary demarcates immature Ti-ltm), it is later restricted to the distal muscle fibers of the Ti-ltm at 45 hr APF (B) (white arrowhead, dashed boundaries demarcate distinct groups of muscle fibers of the Ti-ltm). Lack of Dpr10 expression in the proximal muscles fibers of the Ti-ltm at 45 hr APF (B) are denoted by white arrows. Dpr10 is continuously expressed in the tadm. (scale bar: 25 μm). At 25 hr APF (A’) there is no correlation between Dpr10 protein and αTi-ltm innervation, denoted by white arrowheads. By 45 hr APF (B’) higher levels of Dpr10 protein are seen in regions innervated by the αTi-ltm terminal branches (white arrowheads). (C) Schematic representation of a DIP-α expressing axon (green) innervating Dpr10 expressing muscle precursors (black outlined pink cells) during the course of development between 25 to 45 hr APF, depicting the restriction of Dpr10 to specific muscle fibers targeted by the DIP-α expressing axon. Leg extension occurs between ~30 to 40 hr APF.

Figure 7.

Figure 7—figure supplement 1. Dpr10 expression in the developing Ti-ltm in DIP-α mutant and overexpression contexts.

Figure 7—figure supplement 1.

(A, A’) DIP-α mutant αTi-ltm axon labeled by DIP-α-T2A-Gal4 > 20XUAS-6XGFP (green) retains its ability to target regions of high Dpr10 expression (grey) in the developing Ti-ltm (labeled by Mef2, magenta) at 35 hr APF. (Left: GFP, Mef2 and Dpr10; middle: GFP and Mef2; right: Dpr10). Numbered white-dotted boxes demarcate locations of magnified single-slice insets (A’) (scale bar: 25 μm). White arrowheads demarcate locations of axon innervation by the DIP-α mutant αTi-ltm. (B–C) Overexpression of DIP-α in α-leg MNs using DIP-α-T2A-Gal4 > UAS-DIP-α (labeled by 20XUAS-6XGFP, green), causes accumulation of Dpr10 protein (grey) at sites of axon innervation in the Ti-ltm (labeled by Mef2, magenta), as well as within the primary axon and filopodial projections of αTi-ltm at 25 hr APF (B–B’) and 45 hr APF (C–C’). Numbered white-dotted boxes demarcate locations of magnified single-slice insets (B’,C’). Left: GFP, Mef2 and Dpr10; middle: GFP and Mef2; right: Dpr10). White asterix demarcates a filopodial projection of αTi-ltm that is not physically associated with the Ti-ltm but nevertheless expresses Dpr10. White arrowheads point to regions of axon innervation in the Ti-ltm or within the main axon of αTi-ltm that express high levels of Dpr10.