Ever wonder what that pack of hyenas is laughing about? Well, it may just be your social status. But don’t stress over it too much, because they’ve given us a truly wild idea in this DNA methylation marvel: Having more friends and spending more time with them in early life makes for less stress at adulthood!
The Mara Hyena Project is an ongoing field study of wild spotted hyenas (C. crocuta) in Kenya, led by Kay Holekamp from Michigan State University. In their latest, the team looked at how early social environment impacts the later life stress phenotype and DNA methylation.
First, the team utilized the LUminometric Methylation Assay (LUMA) to assess global (%CCGG) methylation in whole blood:
- More time with mom leads to greater %CCGG methylation
- During the early communal den phase of development, network strength (number of interactions with other hyenas) and betweenness centrality (how central to the network an individual hyena is based on the shortest network path between individuals) both positively associate with %CCGG methylation
- Once cubs are independent from the communal den, network degree (the number of different individuals each hyena interacts with) and strength positively associate with %CCGG methylation and with lower adult stress indicators called fecal glucocorticoid metabolites (fGCMs)
Then, to get a regional look, turned to multiplexed enhanced reduced representation bisulfite sequencing (mERRBS)
- Identified 18 differentially methylated sites (DMSs) that associate with fGCMs
- Four of these 18 DMSs positively associate with fGCMs and negatively associate with maternal grooming, with sites in 5 different genes, TSKU, RAB43, ISY1, ADA, and ZSCAN2
- One of 18 DMSs – the one located at the TSHZ2 gene – negatively associates with fGCMs and positively associates with maternal grooming
First author Zachary Laubach shares, “This study supports this idea that, yes, these early experiences do matter. They seem to have an effect at the molecular level and future stress response—and they’re persistent. The type, timing, and mechanisms that link these early life experiences with stress seem to be important not only in controlled laboratory settings but also in the wild, where animals are subject to natural variation. With respect to the impact of this work, this echoes a growing body of epidemiological work which studies how the timing of an exposure affects a health outcome. The idea is that, as an organism develops, there are certain points in time, often referred to as sensitive periods, when an exposure has a larger and a more persistent effect than if that exposure occurred at a later point in time.”
Get your pack together for the last laugh in Nature Communications, July 2021.