Genetic and environmental modulation of RNA editing

描述（由申请人提供）：早期生活压力是成年抑郁症的一个突出危险因素。在人类和啮齿类动物中，早期生活压力会导致几种生理指标的变化，这些变化一直持续到成年。在遗传上不同的近交系小鼠前脑5-羟色胺较低，自发性焦虑升高，应激反应性增加（Balb/c），早期生活压力导致成年后神经元基因表达的几个变化。这些变化包括5-羟色胺2C（5-HT 2C）受体mRNA亚型的表达增加，这些亚型是由RNA编辑引起的，并编码功能降低的受体。在抑郁自杀者的大脑中也发现了5-HT 2C受体编辑的这种变化。对Balb/c小鼠的研究表明，5-HT 2C受体编辑的变化伴随着与该受体偶联的Gq蛋白α亚基的表达改变。他们进一步表明，在青春期使用抗抑郁药物氟西汀治疗显著降低了由早期生活压力引起的异常增加的5-HT 2C前mRNA编辑，并逆转了G α q蛋白表达的相应改变。与青少年氟西汀在暴露于早期生活压力的小鼠中的作用相似，断奶后环境丰富减少了对成年压力的高行为反应的幅度。然而，与氟西汀相反，断奶后富集并没有改变异常的5-HT 2C前mRNA编辑表型。在该提案中，Balb/c和抗应激C57 Bl/6小鼠之间的交叉培养范例用于测试遗传因素、环境因素和青少年抗抑郁药治疗对5-HT 2C受体编辑表型的调节的影响。它进一步测试了导致暴露于早期生活压力的Balb/c小鼠中5-HT 2C前mRNA编辑增加的潜在机制。一种假设是，早期生活压力通过选择性剪接改变编辑酶ADAR 1/2的不同亚型的表达，以产生具有更高催化活性的mRNA编码酶。通过对转染细胞的研究验证的另一个假设是，G alpha q蛋白是5-HT 2C前体mRNA编辑的血清素依赖性调节的关键介体。最后，分子和解剖学研究将证明，由早期生活压力引起的5-HT 2C前mRNA编辑的变化也伴随着其他基因表达的变化，这些基因是基因表达中表观遗传变化的潜在介导者，基因表达的转录或转录后调节剂，或参与突触功能，基因表达的许多变化在功能上与抑郁症有关，并受到遗传因素、环境影响和抗抑郁治疗的不同调节。

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.