Maternal Programming Gene Expression DNA Methylation

描述（由申请人提供）：母鼠对幼崽的照顾影响大鼠下丘脑-垂体-肾上腺（HPA）对应激反应的发育。因此，自然表现出舔狗/梳理和拱背哺乳频率增加的母狗（即高LG-ABN母狗）的成年后代对压力表现出更温和的HPA反应。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来描述这种母体效应的细胞和分子基础。产妇护理的改变增加了海马中5-羟色胺（5-HT）的周转率，进而通过5-HT7受体激活cAMP的形成，增加蛋白激酶a的活性，增加激活蛋白2 （AP-2）和NGFI-A的表达，通过与相关GR基因启动子序列的直接相互作用，反激活GR基因转录。关键的问题是这些影响的持久性：在后代的一生中，母亲的护理计划如何影响基因表达的差异？我们的研究旨在检验这样一种假设，即这种效应是由位于GR基因启动子区域特定位点的DNA序列的结构变化介导的。这些研究使用体内和体外方法来检查产妇护理如何改变DNA甲基化以及这种DNA化学改变，染色质结构，基因表达和生理之间的关系。方法包括使用亚硫酸氢钠定位分析单核苷酸甲基化，组蛋白修饰和dna -蛋白质相互作用与染色质免疫沉淀分析。我们相信，这些研究有可能提供一个清晰的机制描述，通过母体护理对大脑中的基因表达产生长期影响，从而对表型发育产生影响。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，尽管通常不愿使用这样的描述，但据我们所知，这些研究可能首次描述了有丝分裂后环境事件对DNA结构变化的反应，并可能最终提供环境诱导的DNA甲基化和染色质结构在生命周期中的可塑性的初步研究。

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.