Figure 3. Loss of Dp reduces the size of larval and adult skeletal muscles.

(a) Dp::GFP localizes in DLM nuclei of Dp^GFP pharates. Scale bar, 10 μm. See Supplementary Fig. 2. (b) Arp53D expression in flight muscle is de-repressed in Dp knockdown. RT–qPCR, mean±s.e.m., N=3 samples per genotype, Mann–Whitney test, *P<0.05. (c,d) Muscle size is reduced in Dp-depleted muscles. Transverse sections of pharate thoraces (ventral to the bottom). Each hemithorax contains six DLM (white asterisks, left panel). Scale bar, 50 μm. (c) Paraffin-embedded sections stained with haematoxylin and eosin. DLM4 (dashed black boxes) magnified at the bottom panel. Black arrowheads point the aggregates/clumps. Quantification of total number of DLMs per hemithorax, mean±s.d., N=21, 16 per genotype, Mann–Whitney test, P>0.05. (d) Sections stained with Phalloidin and 4,6-diamidino-2-phenylindole (DAPI; top panel). DLM 4 stained with Phalloidin (middle panel), β-PS integrin to mark the plasma membrane and DAPI (bottom panel). Cluster of myofibrils is outlined (yellow dashed line). Quantification of DLM4 cross-section area per fly (mm²). Area of myofibril clusters, total number of myofibril cluster, total number of myofibrils per cluster, myofibril density per cluster area (μm²), total number of nuclei and density of nuclei per DLM4 area (μm²) are quantified per DLM4, mean±s.e.m., N=8 per genotype, t-test with Welch's correction, **P<0.01; ***P<0.001. Three independent experiments. (e) Muscle size is rescued in thoraces of 2- to 5-day-old UAS-Dp-RNAi;Mef2-GAL4/UAS-Dp adults compared with Mef2-GAL4/UAS-mCherry. Sections stained with Phalloidin and β-PS integrin. Scale bar, 50 μm. Quantification of DLM4 cross-section area per fly (mm²), mean±s.e.m., n=8, 10 per genotype, t-test with Welch's correction, P>0.05. Two independent experiments. (f) Arp53D expression in flight muscles is rescued. Same genotype as in e. Mean±s.e.m., N=3 samples per genotype, Mann–Whitney test, P>0.05. (g,h) Third instar larval body wall muscle area is reduced in (g) Dp-depleted muscles and (h) in Dp^−/− mutant. Body wall muscles VL3 (asterisks) and VL4 stained with Phalloidin. Anterior is to the top. Scale bar, 50 μm. Quantification of VL3 muscle area, mean±s.e.m., unpaired t-test with Welch's correction, P<0.05. Three independent experiments. (g) n=10, 11, (h) n=12, 10 per genotype. Genotypes (b–d,g) Mef2-GAL4/UAS-mCherry-RNAi and UAS-Dp-RNAi;Mef2-GAL4, (h) Dp^a3/+ and Dp^a3/Df(2R)Exel7124.