a (Left): Representative images of H&E-staining of TA muscle cross-sections at day 5 and day 7 post injury from WT and LEMP KO mice. Scale bar, 50 μm. (Right): Statistics on the number of regeneration fibers per unit area. Error bars, standard deviations (n = 10). Statistical analysis was performed using Student’s t test. ***P < 0.001. b MHC immunostaining of satellite cells isolated from WT and LEMP KO mice. MHC: green; DAPI: red. c Quantitation of fusion in WT and LEMP KO satellite cells. Scale bar, 100 μm. Error bars, standard deviations (n = 3). Statistical analysis was performed using Student‘s t test. **P < 0.01, *P < 0.05, ns: not significant. d RT-qPCRs to examine MHC mRNA expression level in satellite cells isolated from WT and LEMP KO mice. The bars show RNA levels relative to GAPDH. Error bars, standard deviations (n = 3). Statistical analysis was performed using Student’s t test. **P < 0.01.

a In situ hybridization to examine the localization of MyolncR4 at different developmental stages of zebrafish embryos with a specific probe targeting zLEMP. hpf, hours post fertilization. Scale bar, 200 μm. b Diagram to show the targeting sequence of the LEMP-AMO. c Representative images of zebrafish at 24 or 48-hpf after injection of different amounts of LEMP-AMO at one-cell stage. Scale bar, 200 μm or 25 μm. d Representative images of zebrafish at 24 or 48-hpf after injection of LEMP-AMO in the presence or absence of the zebrafish LEMP mRNA at one-cell stage. Scale bar, 200 or 25 μm. e MHC immunostaining to examine myofiber alignment in 48-hpf embryos injected with Cntl-AMO, LEMP-AMO, LEMP-AMO with zLEMP mRNA, or LEMP-AMO with mLEMP mRNA, respectively. Scale bar, 10 μm.