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Enriched environments, epigenetics, and offspring.

Enriched environments produce epigenetic changes in young mice--both male and female--that affect the next generation, according to recent studies. Mice raised in an environment that encourages curiosity, exploration, social interaction, and physical activity produce offspring that are less stressed, have brain changes that promote memory and learning, and have higher birth weights compared with offspring from mice raised in isolation or conventional laboratory cages.

In a 2009 study, Junko A. Arai and colleagues exposed 15-day-old ras-grf mice to an enriched environment for two weeks. Ras-grf mice have defective long-term potentiation (LTP), "a form of synaptic plasticity that is known to be important for learning and memory." In previous studies, the researchers had observed that this temporary exposure to an enriched environment leads to normal LTP in these mice for about 2 months before dropping to defective LTP levels found in unexposed ras-grf mice. In this study, the researchers looked at the offspring of enriched mice that were conceived while LTP levels were still normal. They observed that the offspring of female rats exposed to an enriched environment during their adolescence displayed normal LTP even when raised in a conventional environment. Unlike the parents, however, the offspring's LTP levels declined before they were old enough to bear young; the genes themselves had not changed. Arai and colleagues say that environment affected the epigenetics; that is, how the genes are expressed. "The idea that the effect of enrichment in the mother can be passed on to offspring during embryogenesis is consistent with a behavior study from >20 years ago," write the authors, "which showed that exposure of pregnant rats to an enriched environment enhances the maze learning abilities of their offspring, even if the offspring are raised by non-enriched foster mothers" (Kiyono et al. 1985).

Early environment of male mice also has an effect on offspring, according to a 2012 study led by Rahia Mashoodh at Columbia University (New York). Paternal genes in rodents affect a pup's rate of ultrasonic vocalizations, suckling ability, and locomotor activity. These behaviors govern the amount of maternal care that a pup receives. In this experiment, female mice who mated with males raised in an enriched environment exhibited "significantly higher levels of pup nursing across the first week postpartum ... and marginally higher levels of pup licking" than females mated with mice raised in isolation. At weaning, the weight of offspring from enriched males was 0.98 grams greater, on average, than isolated males' offspring. "This growth effect was observed in both male and female offspring and was significant after controlling for maternal care," say the authors.

We know that nutrition and exercise can affect gene expression. The quality of one's environment has epigenetic effects as well.

Arai JA, Li S, Hartley DM, Feig LA. Transgenerational rescue of a genetic defect in long-term potentiation and memory formation by juvenile enrichment. J Neurosci. February 4, 2009;29(5):1496-1502. Available at Accessed November 14, 2013.

Mashoodh R, Franks B, Curley JP, Champagne FA. Paternal social enrichment effects on maternal behavior and offspring growth. PNAS. October 16, 2012;109(suppl.2):17232-17238. Available at Accessed November 14, 2013.

briefed by Jule Klotter
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Title Annotation:Shorts
Author:Klotter, Jule
Publication:Townsend Letter
Article Type:Report
Geographic Code:1USA
Date:Feb 1, 2014
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