Abstract
Variations in maternal care alter the developmental programming of some genes by creating lasting differences in DNA methylation patterns, such as the estrogen receptor alpha (ERα) promoter region. Interestingly, mother rats preferentially lick and groom their male offspring more than females; therefore, we questioned whether the somatosensory stimuli associated with maternal grooming influences potential sex differences in DNA methylation patterns within the developing amygdala, an area important for socioemotional processing. We report a sex difference in the DNA methylation pattern of specific CpG sites of the ERα promoter region within the developing amygdala. Specifically, males have higher levels of ERα promoter methylation contrasted to females. Increasing the levels of maternal stimuli in females masculinized ERα promoter methylation patterns to male-like levels. As expected, higher levels of ERα promoter methylation were associated with lower ERα mRNA levels. These data provide further evidence that the early neonatal environment, particularly maternal care, contributes to sex differences and early programming of the neonatal brain via an epigenetic mechanism.