Dnmt3a-mediated abnormal DNA methylation is associated with myelination deficits in offspring of advanced maternal age rats.

Advanced maternal age (AMA) threatens offspring brain development, yet its neurodevelopment-disrupting mechanisms remain poorly understood. Our prior work has suggested that AMA may impair myelin development in offspring, accompanied by increased Dnmt3a expression and DNA methylation levels in the hippocampus. This study explores whether Dnmt3a mediates myelination defects in offspring of AMA rats. Lentiviral vectors were intracerebroventricularly administered to modulate Dnmt3a expression in AMA offspring after birth. Protein expression was analyzed by western blotting and immunofluorescence at postnatal days (P) 7, 14, and 28. Myelin development was evaluated at P28 using transmission electron microscopy, immunofluorescence, luxol fast blue staining, and glycine silver staining. Cognitive function was assessed using the novel object recognition test from P23 to P24. AMA offspring exhibited impaired oligodendrocyte precursor cell (OPC) maturation and abnormal myelination during early postnatal brain development. Inhibition of Dnmt3a increased the expression of CNPase, MBP, and Olig2, which are associated with oligodendrocyte lineage maturation and myelination, and alleviated myelin deficits and cognitive impairment. Furthermore, Dnmt3a inhibition reduced 5-methylcytosine levels in PDGFR-α-positive cells and decreased Dnmt3a expression in Olig2-positive cells. In contrast, Dnmt3a overexpression did not significantly alter myelination-related phenotypes. In conclusion, Dnmt3a dysregulation could be associated with altered OPC maturation and myelination in AMA offspring, possibly mediated by epigenetic mechanisms involving Olig2. Dnmt3a downregulation partially restores oligodendrocyte lineage maturation, myelin development, and cognitive function. These findings suggest that Dnmt3a may serve as a potential molecular target for further investigation in the prevention of neurodevelopmental impairments associated with AMA.