FIGURE 6

The dystrophin isoform Dmd^∆ex1‐7 lacking exons 1‐7 is partially functional. A, Schematic of the construct used to generate the transgenic line Tg(αAcry:GFP,acta1:dmdGFP). The acta1 promoter directed full‐length dystrophin into muscle and the αA‐crystallin promoter (αAcry) drove GFP expression into the lens for rapid identification of transgenic animals. pA indicates SV40 polyA signal. B, In 3‐dpf‐old Tg(cry:GFP,acta1:dmdGFP) larvae, fluorescence of the Dmd‐GFP fusion protein was detected at the vertical myosepta (arrowheads). C, Polarized light visualized the muscle of 3‐dpf‐old larvae. Whereas the birefringence of non‐transgenic siblings appeared uniform, the birefringence of dmd^pc2 homozygotes appeared patchy. In contrast, in the transgenic background of Tg(cry:GFP,acta1:dmdGFP) the birefringence of dmd^pc2 homozygotes and siblings was comparable. D, Quantification of the birefringence followed by rescaling to non‐transgenic siblings revealed that the birefringence of dmd^pc2 homozygotes transgenic for Tg(cry:GFP,acta1:dmdGFP) was not significantly changed compared with non‐transgenic dmd^pc2 siblings. Crosses represent averaged grey values of at least five 72‐hpf‐old larvae. Black bars represent mean ± SEM and n.s. non‐significant. Significance was determined by one‐way ANOVA with Tukey's multiple comparisons post hoc test (***P < 0.001, n = 6). E, Within Tg(cry:GFP,acta1:dmd^∆ex1‐7GFP) larvae, N‐terminally truncated dystrophin fused to GFP localized to the vertical myosepta as indicated by the GFP fluorescence. F, After rescaling to non‐transgenic siblings, the birefringence of dmd^pc2 homozygotes transgenic for Tg(cry:GFP,acta1:dmd^∆ex1‐7GFP) was significantly ameliorated compared with non‐transgenic dmd^pc2 homozygotes, but significantly reduced compared with non‐transgenic dmd^pc2 siblings. Crosses represent averaged grey values of at least five 72‐hpf‐old larvae. Black bars are mean ± SEM Significance was determined by one‐way ANOVA with Tukey's multiple comparisons post hoc test (***P < 0.001, n = 6). G, At 6 dpf, the maximal force generated by dmd^pc2 homozygotes positive for Tg(cry:GFP,acta1:dmd^∆ex1‐7GFP) was significantly stronger compared with non‐transgenic dmd^pc2 homozygotes, but significantly reduced compared with non‐transgenic dmd^pc2 siblings. Crosses represent individual larvae and black bars mean ± SEM. Significance was determined by one‐way ANOVA with Tukey's multiple comparisons post hoc test (**P < 0.01, n = 4)