1. Weaver et al propose that among rats, maternal behavior towards newborn pups influences their cortisol response to stress via epigenetic mechanisms that change the expression of glucocorticoid receptor gene for the rest of the pup’s life. They argue that because epigenetic patterns are established at specific developmental periods, there is extreme time sensitivity to when the pup is exposed to particular maternal behaviors (licking and grooming, in this case), and maternal behavior before or after that sensitive period window is not as important. Do you think this mechanism is relevant in humans? If so, what behaviors are most analogous to “maternal licking and grooming”?
Yes, I think this mechanism is relevant in humans. Maternal licking and grooming by rats towards their newborn pups reminds me of mothers engaging in skin-to-skin contact with their child directly after the birth of their child, and remaining physically and emotionally engaged with their child in the first few years of life.
2. Gruenewald, in contrast, emphasize the cumulative effects of SES adversity on a multi-system allostatic load measure. Do you think that the Gruenewald findings are consistent, inconsistent, or unrelated to the Weaver findings? Explain.
Gruenewald’s finding seem inconsistent to the Weaver findings because Weaver focuses on the importance of a sensitive period in early development, whereas Gruenewald’s findings are in support of the cumulative risk hypothesis which emphasizes the cumulative effect of SES adversity over the entirety of the life course.
3. Hertzmann and Boyce argue that “it is not genes or environment, nor is it genes and environment, but rather it is gene-by-environment interactions that influence developmental trajectories.” To what extent do you think that GxE interactions can contribute to major disparities along racial/ethnic, socioeconomic, or geographic dimensions?
I agree with Hertzmann and Boyce that to a certain extent, gene-by-environment interactions can contribute to disparities along racial/ethnic, socioeconomic, or geographic dimensions. In a study by Taylor et al. as a part of the Jackson Heart Study, researchers identified five SNPs that interacted with perceived discrimination on systolic blood pressure and three SNPs that interacted with perceived discrimination diastolic blood pressure in African-Americans. Although this is only one example, I do believe that it illustrates the role that stress can play in exacerbating a genetic predisposition to disease, and considering that stressors like discrimination frequently occur in racial/ethnic minority groups and individuals with lower SES, it demonstrates how the gene-by-environment interactions can contribute to the disparities that those groups face.
Taylor JY SY, Barcelona de Mendoza V, Ifatunji M, Rafferty J, Fox ER, Musani SK, Sims M, Jackson JS. The combined effects of genetic risk and perceived discrimination on blood pressure among African Americans in the Jackson Heart Study. Medicine. 2017:1 - 8.