Maternal Programming of Gene Expression Through DNA Methylation

描述（由申请方提供）：母体对幼仔的护理影响大鼠下丘脑-垂体-肾上腺（HPA）对应激反应的发育。因此，母亲的成年后代自然表现出增加的频率舔/梳理和拱背护理（即，高LG-ABN母亲）显示更温和的HPA反应的压力。这些影响，部分是由海马糖皮质激素受体（GR）基因表达的变化介导的。我们提出了一个工作模型，描述这种母体效应的细胞和分子基础。母亲护理的变化增加了海马体中5-羟色胺（5-HT）的周转，这反过来又通过5-HT 7受体激活cAMP形成，并增加了蛋白激酶A活性和激活蛋白-2（AP-2）和NGFI-A的表达增加，激活蛋白-2和NGFI-A通过与相关GR基因启动子序列的直接相互作用反式激活GR基因转录。关键的问题是这些影响的持久性：在后代的生命周期中，母亲的护理是如何规划基因表达的差异的？我们的研究旨在研究这样的影响是由位于GR基因启动子区域内特定位点的DNA序列的结构变化介导的假设。这些研究使用体内和体外方法来研究孕产妇护理如何改变DNA甲基化以及DNA，染色质结构，基因表达和生理学的化学改变之间的关系。这些方法包括使用亚硫酸氢钠作图分析单核苷酸甲基化、组蛋白修饰和使用染色质免疫沉淀分析的DNA-蛋白质相互作用。我们相信，这些研究有可能提供一个明确的机制，孕产妇保健发挥长期的影响，在大脑中的基因表达，从而表型发展的描述。从本质上讲，这些研究直接研究了基因X环境相互作用与特定功能性状的关系。最后，虽然通常不愿意使用这样的描述，据我们所知，这些研究可能提供了第一个描述的结构变化的DNA在有丝分裂后，环境事件，并可能最终提供初步的研究环境诱导的可塑性DNA甲基化和染色质结构的寿命。

DESCRIPTION (provided by applicant): Maternal care of pups influences the development of hypothalamic-pituitary-adrenal (HPA) responses to stress in the rat. Thus, the adult offspring of mothers that naturally show an increased frequency of pup licking/grooming and arched back nursing (ie, High LG-ABN mothers) show more modest HPA responses to stress. These effects are, in part, mediated by changes in hippocampal glucocorticoid receptor (GR) gene expression. We propose a working model describing the cellular and molecular basis for this maternal effect. The changes in maternal care increase serotonin (5-HT) turnover in the hippocampus which, in turn, activates cAMP formation via a 5-HT7 receptor and to increase protein kinase A activity and increased expression of activator protein-2 (AP-2) and NGFI-A which transactivate GR gene transcription via direct interaction with relevant GR gene promoter sequences. The critical questions concern the apparent permanence of these effects: How might maternal care program differences in gene expression over the lifespan of the offspring? Our studies are designed to examine the hypothesis that such effects are mediated by structural changes in DNA sequences located at specific sites within the promoter region of the GR gene. These studies use both in vivo and in vitro approaches to examine how maternal care alters DNA methylation and the relationship between such chemical alterations of the DNA, chromatin structure, gene expression and physiology. The methods include analysis of single nucleotide methylation using sodium bisulfite mapping, histone modifications and DNA-protein interactions with chromatin immunoprecipitation assays. We believe that these studies hold the possibility of providing a clear description of the mechanisms by which maternal care exerts long-term effects over gene expression in the brain and thus of phenotypic development. In essence, these studies directly examine gene X environment interactions in relation to specific, functional trait. Finally, although normally loath to use such descriptions, to the best of our knowledge these studies potentially provide the first description of structural changes in DNA in response to a post-mitotic, environmental event, and may ultimately provide the initial studies of environmentally-induced plasticity in DNA methyation and chromatin structure over the lifespan.