Life experiences shape us in ways that are hard to imagine, whether it’s a catch-phrase from a favorite TV show slipping into our vocabulary ,or how much your mother licked you while you were child (We know that sounds weird for humans, but licking just happens to be a measure of maternal care in rodents). While the majority of the research on early experiences has been focused on males, leaving many open questions about how gender would influence this complex gene-environment interaction, a team from the University of Toronto, lead by Patrick McGowan, have provided some extensive detail about how early life maternal care can alter gene regulation and related behaviors in female offspring.
Mother rats show natural variation in their maternal care, both between and within litters, specifically in terms of licking and grooming (LG) their pups. These early experiences create epigenetic signatures that not only have immediate effects but also explain a lot of the more mysterious long-term consequences. Here’s what was found in the hippocampus of female offspring when comparing high LG to low LG:
- Both between and within litter variation in maternal LG produces increased locomotor activity in the ‘loved’ children.
- High LG siblings show reduced anxiety compared to their low LG siblings, regardless of how much ‘love’ the mother had to give.
- Surprisingly, the lowest licked from the low LG litters and highest licked from the high LG litters showed a similar suppressed corticosterone (CORT) responses to stress.
- Differences may lay in the fact that the high LG litters have increased expression of a glucocorticoid receptor, which was negatively correlated with the CORT response.
- This appears to be due to 2 CpG sites in the GR17 promoter that show significantly higher DNA methylation in high LG offspring.
Overall, this study offers one of the first looks at how the variation in maternal care can affect females. While the results do appear to suggest sex specific differences, the authors also note the possibility of differential methods to observe maternal care impacting the results.
Learn about the gender effects of maternal care in Behavioral Neuroscience, September 2014