3-methyl-4-nitrophenol disturbs the maternal-to-zygotic transition of early embryos by damaging mitochondrial function and histone modification.

3-methyl-4-nitrophenol (PNMC), a chemical prevalent in various industries for drug, dye, and leather production, also serves as a primary byproduct of organophosphate insecticides. Despite its global recognition as an endocrine disruptor with documented reproductive toxicity, its detrimental impact on preimplantation embryonic development has yet to be thoroughly investigated. In this study, through the in vitro culture of mice embryos, it was initially observed that even low concentrations of PNMC exposure led to a significant reduction in blastocyst formation and a sharp decline in the ratio of inner cell mass within the blastocysts. SMART-seq2 transcriptome sequencing further confirmed that PNMC treatment disrupted global gene expression in 2-cell embryos, with differentially expressed genes enriched in multiple signaling pathways, including those related to autophagy, apoptosis, fertilization, embryonic development, transcription, and mRNA processing. Integration of transcriptome data with open databases revealed that both zygotic genome activation genes and maternal factors experienced significant transcript-level disruptions. Moreover, the study demonstrated that these gene expression changes were closely associated with mitochondrial dysfunction, evidenced by diminished mitochondrial membrane potential, reduced ATP production, aberrant expression of mitochondria-related genes, increased ROS accumulation, and heightened DNA damage in PNMC-treated embryos. Additionally, PNMC exposure induced defects in histone modification, as shown by altered levels of H3K9me3 and H3K27me3, H3K9ac and H3K27ac. Lastly, the findings indicated that PNMC triggered apoptosis in embryos, validated by elevated BAX and CASPASE3 expression, alongside positive TUNEL staining. In summary, PNMC exposure impairs the maternal-to-zygotic transition, likely through mitochondrial dysfunction and histone modification, culminating in developmental arrest and apoptosis in mouse preimplantation embryos.