Elevated RIF1 participates in the epigenetic abnormalities of zygotes by regulating histone modifications on MuERV-L...

Maternal obesity impairs embryonic developmental potential and significantly increases the risks of metabolic disorders in offspring. However, the epigenetic transmission mechanism of maternal metabolic abnormalities is still poorly understood.

We established an obesity model in female mice by high-fat diet (HFD) feeding. The effects of the HFD on the developmental potential of oocytes and embryos, the metabolic phenotype, and epigenetic modifications were investigated. The efficacy of metformin administration was assessed. Finally, the regulatory pathway of epigenetic remodeling during zygotic genome activation (ZGA) was explored.

Maternal HFD consumption significantly impaired glucose tolerance and increased the risk of metabolic disorders in F0 and F1 mice. Maternal HFD consumption also decreased embryonic developmental potential, increased reactive oxygen species (ROS) and γH2AX levels, and reduced the mitochondrial membrane potential (MMP) within oocytes, causing high levels of oxidative stress damage and DNA damage. Starting with this clue, we observed significantly increased RIF1 levels and shortened telomeres in obese mice. Moreover, significant abnormal DNA methylation and histone modification remodeling were observed during ZGA in obese mice, which may be coregulated by RIF1 and the ZGA marker gene MuERV-L. Metformin treatment reduced RIF1 levels, and partially improved ZGA activation status by rescuing epigenetic modification remodeling in oocytes and preimplantation embryos of obese mice. RIF1 knockdown experiments employing Trim-Away methods showed that RIF1 degradation altered the H3K4me3 and H3K9me3 enrichment and then triggered the MuERV-L transcriptional activation. Moreover, ChIP-seq data analysis of RIF1 knockouts also showed that RIF1 mediates the transcriptional regulation of MuERV-L by changing the enrichment of H3K4me3 and H3K9me3 rather than by altered DNA methylation.

Elevated RIF1 in oocytes caused by maternal obesity may mediate abnormal embryonic epigenetic remodeling and increase metabolic risk in offspring by regulating histone modifications on MuERV-L, which can be partially rescued by metformin treatment.