Rat dams can be divided based on their maternal care into high, mid, or low licking/grooming (LG) mothers. The pups raised by low LG mothers have less glucocorticoid receptor (GR) mRNA brought about by GR gene methylation. Consequently, the offspring of low-LG mothers have higher anxiety and impaired learning when adults. Because it is elicited by maternal behavior, such methylation is maintained across generations. However, upon cross-fostering (change of low LG mother to high LG mother) the methylation level of the GR promoter is restored. What does this result imply?
How do epigenetic modifications such as DNA methylation affect normal gene function?