Epigenetic transgenerational inheritance of altered stress responses

Abstract

Ancestral environmental exposures have previously been shown to promote epigenetic transgenerational inheritance and influence all aspects of an individual's life history. In addition, proximate life events such as chronic stress have documented effects on the development of physiological, neural, and behavioral phenotypes in adulthood. We used a systems biology approach to investigate in male rats the interaction of the ancestral modifications carried transgenerationally in the germ line and the proximate modifications involving chronic restraint stress during adolescence. We find that a single exposure to a common-use fungicide (vinclozolin) three generations removed alters the physiology, behavior, metabolic activity, and transcriptome in discrete brain nuclei in descendant males, causing them to respond differently to chronic restraint stress. This alteration of baseline brain development promotes a change in neural genomic activity that correlates with changes in physiology and behavior, revealing the interaction of genetics, environment, and epigenetic transgenerational inheritance in the shaping of the adult phenotype. This is an important demonstration in an animal that ancestral exposure to an environmental compound modifies how descendants of these progenitor individuals perceive and respond to a stress challenge experienced during their own life history.

Fig. 1.

Behavior analysis. (A) In OF tests, C-L nonstress males spent more time in corners than did V-L nonstress males. (B) Heat map showing occupancy for group means in the OF from the bird’s eye view. Red indicates greater time spent at any given position. Arrows indicate change in activity as a consequence of stress. (C) Overhead view of group mean tracing of movement within a schematic of the testing chamber for animals in Soc 1. “E” indicates an empty stimulus cage; “A” indicates a stimulus cage containing an animal. (D) Overhead view of group mean tracing of movement within a schematic of the testing chamber for animals in Soc 2. “N” indicates a stimulus cage containing a novel male; “F” indicates a stimulus cage containing a familiar animal. (E) Evidence of transgenerational epigenetic modification on response to CRS on social bonding.

Fig. 2.

Phenotype analysis at different levels of biological organization. Leftmost columns depict effects of lineage (difference between C-L and V-L) under nonstress and stress conditions. An asterisk above a peak or a valley indicates a significant effect of treatment in that behavioral test (P < 0.05). Differences in phenotype calculated by permutation analysis on this dataset yielded the p results shown beneath each landscape, indicating the degree to which the landscape is changed. A peak for a trait indicates a greater result in V-L (V) males, whereas a valley indicates a greater result in C-L (C) males. Rightmost columns depict effects of stress (difference between nonstress and stress) in C-L and V-L males. A peak for a trait indicates a greater result in stress (S) conditions, whereas a valley indicates a greater result in nonstress (NS) conditions. Nodes represent group means of percentage maximum or Z scores (see SI Materials and Methods for specifics). (A) Body phenotype. Clockwise nodes: BW; ASI, adrenosomatic index; CORT; Lept, leptin level; TESTO; and GSI, gonadosomatic index. (B) Behavior phenotype. Clockwise nodes: Soc 2, measure of social novelty and working memory; OF; FS; and Soc 1, measure of social approach, anxiety, and exploration. (C) Brain metabolism phenotype. Clockwise nodes: BLA, CeAmy, MeAmy, CA1, CA3, CoAmy, PMCo, MePD, and ST. (D) Essential phenotype or the three most influential measures from each category (physiology, behavior, and brain). Clockwise nodes: TESTO, CORT, OF, Soc 1, Soc 2, MePD metabolic activity, ST metabolic activity, CA1 metabolic activity, and BW.

Fig. 3.

Direct-connection networks for genes in CRTX (gene lists 5–8; A) or CA1 (gene lists 9–12; B) obtained by global literature analysis using Pathway Studio 7.0 software (Ariadne Genomics). (A) For cortex, only 22 directly connected genes of 330 unique genes (no ESTs included) from combined lists 1–4 are shown. (B) For CA1, 47 genes of 430 unique genes (no ESTs included) from combined lists 9–12 are shown. The rest of genes are not connected and not shown.