Pre-reproductive stress in adolescent female rats alters maternal care and DNA methylation patterns across generations

Stress during development affects maternal behavior and offspring phenotypes. Stress in adolescence is particularly consequential on brain development and maturation, and is implicated in several psychiatric disorders. We previously showed that pre-reproductive stress (PRS) in female adolescent rats affects behavior and corticotropin releasing hormone receptor 1 (CRHR1) expression in first- (F1) and second- (F2) generation offspring. We further showed that offspring phenotypes are partially reversed by post-stress treatment with fluoxetine (FLX) or the CRHR1 antagonist NBI27914 (NBI). Epigenetic processes, such as DNA methylation, are implicated in the stress response and interact with maternal care quality across generations. Here, we asked whether PRS and FLX or NBI exposure would affect maternal care and global DNA methylation in the brains of exposed dams and their adult F1 and paternally-derived F2 offspring. We found that PRS decreased self-care while increasing pup-care behaviors. PRS also increased DNA methylation in the amygdala of dams and their F1 male offspring, but decreased it in F2 females. Drug treatment had no effect on maternal care, but affected DNA methylation patterns in F0 and F1 generations. Furthermore, PRS altered the expression of DNA methylating enzymes in brain, blood and oocytes. Finally, maternal care variables differentially predicted methylation levels in PRS and control offspring. Thus, the effects of adolescent stress are long-lasting and impact methylation levels across three generations. Combined with our findings of epigenetic changes in PRS-exposed oocytes, the present data imply that biological changes and social mechanisms act in concert to influence adult offspring phenotypes.

发育过程中的应激会影响母性行为与子代表型。青春期应激对大脑发育与成熟的影响尤为显著，且与多种精神疾病密切相关。我们此前的研究证实，青春期雌性大鼠的生殖前应激（pre-reproductive stress, PRS）会影响其子一代（F1）和子二代（F2）的行为以及促肾上腺皮质激素释放激素受体1（corticotropin releasing hormone receptor 1, CRHR1）的表达；进一步研究发现，应激后使用氟西汀（fluoxetine, FLX）或CRHR1拮抗剂NBI27914（NBI）进行干预，可部分逆转子代的异常表型。表观遗传调控过程（如DNA甲基化）参与应激应答，并在跨代传递过程中与母性照料质量相互作用。本研究旨在探究PRS暴露以及FLX或NBI干预是否会影响暴露母鼠及其成年F1代、父系来源F2代子代大脑中的母性行为与全基因组DNA甲基化水平。研究结果显示，PRS会减少母鼠的自我照料行为，同时增加其育幼行为；PRS还会提升母鼠及其F1代雄性子代杏仁核中的DNA甲基化水平，但会降低F2代雌性个体的该指标。药物处理对母性行为无显著影响，但会改变F0代与F1代的DNA甲基化模式。此外，PRS会改变大脑、血液以及卵母细胞中DNA甲基化酶的表达水平。最后，母性行为变量可差异性预测PRS组与对照组子代的甲基化水平。综上，青春期应激的影响具有长期持久性，可跨三代影响DNA甲基化水平。结合我们在PRS暴露卵母细胞中观察到的表观遗传变化，本研究数据表明，生物学改变与社会机制协同发挥作用，共同影响子代成年后的表型。