Liver steatosis and lipid dyshomeostasis manifest during early development in pex1 mutant larvae. (A) Brightfield (left) and Oil-Red O (ORO) staining (right) of 13 dpf zebrafish larvae. Robust neutral-lipid accumulation is confined to the liver of pex1–/– larvae compared with wild-type (WT) and heterozygous siblings. Scale bar, 1 mm. (B) Incidence of ORO-positive (steatotic) livers at 13 dpf; n = 20 larvae per genotype. (C) Log2 fold change of pristanic and phytanic acid in pex1–/– versus WT larvae at 13 dpf measured by LC-MS in whole-larva extracts. Bars represent means ± SDs of five independent replicates, each replicate being a pool of five larvae (n = 5). (D) Heatmap of fatty acid (FA) species profiled by LC-MS. Columns represent biological replicates (pools of five larvae at 11 dpf); rows represent individual FAs. The numerical values on the right correspond to KO/WT log2 ratios and statistical significance was assessed with multiple unpaired Student’s t-test: *p < 0.033; **p < 0.0021, ***p < 0.0002, ****p < 0.0001. Crosses on white background indicate missing values. (E) Stacked bar plots of the FA composition of the indicated lipid classes determined by targeted lipidomics at 13 dpf. Data are means ± SDs of five biological replicates (pools of 15 larvae) normalized to DNA content. Statistical significance in panels C,E was assessed with an unpaired Welch’s t-test (WT vs. pex1–/–). *p < 0.033; **p < 0.0021, ***p < 0.0002, ****p < 0.0001.
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