A The targeted loci were near the translation start code ATG of the gene mpv17. B The agarose gel electrophoresis results of the T7E1 assay for the screening of mpv17 knocked out zebrafish. The marker is DL1000 and the lane number shows different samples. The 397 bp band indicates the wild-type gene, and the lanes with 227 and 170 bp bands show the mutated genes. C The amino acid alignment of the mpv17 protein sequence in wild-type, tra mutant, and mpv17^−/− zebrafish in this study. D One-month-old wild-type and mpv17^−/− zebrafish larvae.

A The mpv17^−/− zebrafish exhibited a decreased survival ratio in the first month. n = 1160 for 5 dpf, 993 for 10 dpf, 227 for 15 dpf and 176 for 26 dpf. B The growth of the mpv17^−/− zebrafish was decreased and even stopped after 14 days. The difference in the average length between mpv17^−/− and the pooled (mpv17^+/+ and mpv17^+/−) larvae was increased. C The mpv17 mRNA can rescue the mpv17^−/− zebrafish, and the proportion of mpv17^−/− zebrafish in the rescue group was less than the control. Error bars were indicated with ±SEM, ***p < 0.005.

A In situ hybridization analysis of myogenic marker gene myod at 24 hpf. Scale bar = 250 μm. B Confocal image of fast and slow muscle at 72 hpf. Antibodies F310 and F59 were used for staining the fast and slow muscle fiber, respectively. Scale bar = 50 μm. C Paraffin section and H&E staining analysis of the skeletal muscle structure in the 1-month-old fish. D The relative mRNA expression levels of the genes involved in the development of muscles.

A The contents of the DAG, TAG, NEFA, and glucose were measured at 7 dpf stage. B The content of ATP was evaluated at 7 dpf. C The relative mRNA expression levels of genes involved in the TAG metabolism in mpv17^−/− larvae with or without normal mitochondria injection. D The bodyweight of the mpv17^−/− larvae with or without mitochondria injection. Error bars were indicated with ±SEM, *p < 0.05, **p < 0.01, ****p < 0.001.

A In situ hybridization with RNA probe tfa at 3 dpf. Wild-type was in the upper, mpv17^−/− in the middle, and the lower was the mpv17^−/− larvae rescued with mpv17 mRNA. B In situ hybridization of larvae at 5 dpf using tfa probe. C The expression level of genes tfa. Error bars were indicated with ±SEM, *p < 0.05. D The expression levels of genes involved in liver development. Error bars were indicated with ±SEM, **p < 0.01, ***p < 0.005. E H&E staining paraffin-embedded sections of the liver in 1-month-old zebrafish. The black frames were enlarged as shown on the right.

A TEM image of the skeletal muscle for the larvae at 7 dpf. The magnification was ×2500 in the upper panel and ×11,500 in the lower panel. Red arrowhead indicated the mitochondria in the skeletal muscles. B The number of the mitochondria per 100 μm² (upper) and the diameter of the mitochondria in the skeletal muscle (lower). Error bars were indicated with ±SEM, *p < 0.05 and **p < 0.01.