Fig. 4

A–D Representative Z projections of 3D confocal images of wt and polg^{sa9574/sa9574} liver at 8 and 16 dpf. The quantification of liver-specific fluorescence from the lfabp10a:DsRed transgene (E) indicates reduced liver size in 16 dpf mutants. F–I Reference bright field images (F, G) and light microscopy analysis of muscle birefringence (H, I) in wt and polg^{sa9574/sa9574} embryos at 3 dpf. The birefringence quantification (see Methods) shows reduced signal in mutants (J). K–N Confocal images of the Tg(Hsa.Cox8a:MLS-EGFP)^ia301 mitochondrial marker (mitoEGFP) in wt (K, M) and polg^{sa9574/sa9574} (L, N) at 16 dpf. The relative quantification of integrated density (O) indicates a reduced mitochondrial mass. P The relative quantification of mtDNA copy number, in wt and polg sa9574 mutants, shows a significant reduction of mtDNA in homozygotes. Data are presented as mean ± SEM and were generated from three different experiments, each containing six embryos per genotype and treatment condition (*p < 0.05; **p < 0.01; N = 6, in triplicate). Q, R TEM analysis of mitochondria in 16 dpf skeletal muscle fibres (sm) of wt and polg^{sa9574/sa9574} detects vesicular cristae with “honeycomb” arrangement inside the mutated mitochondria (indicated by black arrowheads). S Quantification of aberrant morphologies; ***p < 0.001; N = 8 independent TEM images per condition, in triplicate.