Genetic and environmental modulation of RNA editing

描述(由申请人提供)：早期生活压力是成人起病抑郁疾病的显著危险因素。在人类和啮齿动物中，早期的生活压力都会导致几种生理指标的变化，这些变化会持续到成年。在一种遗传上截然不同的近交系小鼠中，前脑5-羟色胺降低，焦虑自发升高，应激反应增强(Balb/c)，早期生活应激导致成年后神经元基因表达的几个变化。这些变化包括5-HT2C(5-HT2C)受体亚型的表达增加，这些亚型是由RNA编辑引起的，编码功能减弱的受体。在抑郁症自杀受害者的大脑中也发现了5-HT2C受体编辑的这种变化。对Balb/c小鼠的研究表明，5-HT2C受体编辑的变化伴随着与该受体偶联的GQ蛋白的阿尔法亚单位的表达变化。他们进一步表明，在青春期使用抗抑郁药物氟西汀显著降低了由于早期生活压力而导致的异常增加的5-HT2C前mRNA编辑，并逆转了GαQ蛋白表达的相应变化。类似于青春期氟西汀对暴露在早期生活压力下的小鼠的影响，断奶后的环境丰富降低了对成年应激的高度行为反应的幅度。然而，与氟西汀相比，断奶后的浓缩并没有改变异常的5-HT2C前mRNA编辑表型。在这项建议中，使用Balb/c和耐应激C57BL/6小鼠之间的交叉培养范式来测试遗传因素、环境因素和青少年抗抑郁药物治疗对5-HT2C受体编辑表型调节的影响。它进一步测试了导致暴露在早期生活应激下的Balb/c小鼠5-HT2C前mRNA编辑增加的潜在机制。一种假设是，早期生活应激通过选择性剪接改变编辑酶ADAR1/2的不同亚型的表达，以产生编码具有更高催化活性的酶的mRNA。通过对转基因细胞的研究验证的另一种假设是，GαQ蛋白是5-HT2C前体mRNA编辑的5-羟色胺依赖调节的关键中介。最后，分子和解剖学研究将证明，早期生活应激导致的5-HT2C前mRNA编辑的变化也伴随着其他基因表达的变化，这些基因要么是基因表达表观遗传变化的潜在中介，要么是基因表达的转录或转录后调节因子，要么参与突触功能，并且这些基因表达的许多变化在功能上与抑郁有关，并受到遗传因素、环境影响和抗抑郁药物治疗的差异调节。

DESCRIPTION (provided by applicant): Early life stress is a prominent risk factor for adult-onset depressive illness. In both humans and rodents, early life stress leads to changes in several physiological measures that persist into adulthood. In a genetically distinct inbred strain of mice with lower forebrain serotonin, spontaneously elevated anxiety, and increased stress reactivity (Balb/c), early life stress leads to several changes in neuronal gene expression in adulthood. These changes include increased expression of serotonin 2C (5-HT2C) receptor mRNA isoforms that result from RNA editing and encode receptors with reduced function. Such changes in 5-HT2C receptor editing have also been found in brains of depressed suicide victims. Studies on Balb/c mice showed that changes in 5-HT2C receptor editing are accompanied by altered expression of the alpha subunit of Gq protein that couples to this receptor. They further showed that treatment with the antidepressant drug fluoxetine during adolescence significantly decreased the abnormally increased 5-HT2C pre-mRNA editing that resulted from early life stress and also reversed corresponding alterations in G alpha q protein expression. Similar to the effect of adolescent fluoxetine in mice exposed to early life stress, postweaning environmental enrichment diminished the magnitude of hightened behavioral responses to adult stress. However, in contrast to fluoxetine, postweaning enrichment did not alter the abnormal 5-HT2C pre-mRNA editing phenotype. In this proposal, a cross-fostering paradigm between Balb/c and stress-resistant C57Bl/6 mice is used to test the impact of genetic factors, environmental factors, and adolescent antidepressant treatment on the modulation of 5-HT2C receptor editing phenotypes. It further tests potential mechanisms leading to increased 5-HT2C pre-mRNA editing in Balb/c mice exposed to early life stress. One hypothesis is that early life stress alters the expression of distinct isoforms of the editing enzymes ADAR1/2 via alternative splicing to yield mRNA encoding enzymes with higher catalytic activities. Another hypothesis, tested with studies on transfected cells, is that G alpha q protein is a critical mediator of the serotonin-dependent regulation of 5-HT2C pre-mRNA editing. Finally, molecular and anatomic studies will demonstrate that changes in 5-HT2C pre-mRNA editing that result from early life stress are also accompanied by changes in the expression of other genes that are either potential mediators of epigenetic changes in gene expression, transcriptional or post-transcriptional modulators of gene expression, or involved in synaptic functions, and that many of these changes in gene expression are functionally linked to depression and differentially modulated by genetic factors, environmental influences, and antidepressant treatment.