RNA editing in a transgenic mouse model of behavioral despair and anxiety.

描述(申请人提供)：人类精神障碍的小鼠模型表明，慢性压力会导致抑郁。缺乏5HT2CR的小鼠表现出应激反应、多动、食欲增加和肥胖的迹象。5HT2CR mRNA由两种酶ADAR1和ADAR2编辑，这两种酶属于作用于RNA(ADAR)的腺苷脱氨酶家族。ADAR1和ADAR2催化mRNA中腺苷向肌苷的转化，因此具有改变氨基酸密码子的能力，从而产生多种蛋白质异构体。ADAR2能够自动编辑自己的转录本，从而产生截短的蛋白质。为了测试自动编辑是否是一种调节机制，我们建立了过量表达ADAR2基因的ADAR2转基因小鼠。其结果是产生了一种具有独特表型变化的小鼠。首先，转基因小鼠变得极度肥胖，这是成熟的开始。配对喂养研究表明，ADAR2转基因小鼠表现出更多的食物摄入量，没有任何明显的代谢失调。在肥胖之前，ADAR2转基因小鼠的血糖、胰岛素和瘦素水平正常，但皮质酮水平升高。最具挑衅性的是，与年龄和体重匹配的对照小鼠相比，ADAR2转基因小鼠在Porsolt游泳和尾部悬挂试验中都增加了不动时间。波索尔特游泳和尾部悬吊试验可用于筛选抗抑郁药物，具有重复性和可预测性。这可能表明ADAR2转基因小鼠是一种抑郁症相关行为的模型。有几条证据表明，5HT2CR与包括抑郁症在内的精神疾病有关。由于RNA编辑而导致的5HT2CR的获得或丢失是产生精神病理学的潜在机制。ADAR2 RNA编辑的后果之一是5HT2CR发生变化。目前要检验的假设是，ADAR2转基因小鼠改变了与抑郁症有关的脑亚区的5HT2CR编辑，因此具有钝化的5-羟色胺突触功能，从而诱导抑郁症样行为变化。进一步表征ADAR2转基因小鼠大脑中抑郁相关行为和5HT2CR的区域RNA编辑，以及它们对特定抗抑郁药物的反应，将为评估潜在有价值的心理抑郁动物模型和深入了解这种形式的情感障碍的机制提供机会。 公共卫生相关性：申请人最近开发了一种新的转基因小鼠品系，该品系可能对心理抑郁的治疗具有直接的临床相关性。这项应用着重于验证ADAR2转基因小鼠作为心理抑郁模型的有效性，以及5-羟色胺2C受体RNA编辑导致抑郁的作用。该模型也可能有助于研究抑郁症相关的神经元底物或基因座。从心理抑郁的啮齿动物模型预测临床结果可能进一步被证明有助于理解抗抑郁药物的有效性和耐受性。

DESCRIPTION (provided by applicant): Mouse models of human psychiatric disorders show that chronic stress can lead to depression. Mice lacking 5HT2CR show signs of stress response, hyperactivity, increased appetite and obesity. 5HT2CR mRNA is edited by two enzymes ADAR1 and ADAR2 that belong to a family of enzymes known as adenonsine deaminases that act on RNA (ADAR). ADAR1 and ADAR2 catalyze the conversion of adenosine to inosine in mRNA and therefore have the ability to change amino acid codons that can produce numerous isoforms of proteins. ADAR2 is able to autoedit its own transcript resulting in a truncated protein. To test whether autoediting is a regulatory mechanism, ADAR2 transgenic mice were generated that over express ADAR2 cDNA. The result was the development of a mouse with unique set of phenotypic alterations. First the transgenic mice became extremely obese that was mature onset. Paired feeding studies showed ADAR2 transgenic mice exhibit increased food intake without any apparent metabolic dysregulation. Prior to obesity the ADAR2 transgenic mice have normal plasma glucose, insulin and leptin levels but they have elevated levels of corticosterone. Most provocative is that when compared with age and weight-matched control littermates, ADAR2 transgenic mice have increased immobility time in both the Porsolt swim and tail suspension test. The Porsolt swim and tail suspension tests are reproducible and predictable for screening antidepressants. This may suggest that ADAR2 transgenic mice are a model of depression related behaviors. Several lines of evidence have implicated 5HT2CR in psychiatric disorders including depression. A gain or loss of 5HT2CR as a result of RNA editing is a potential mechanism for generating psychopathology. One of the consequences of ADAR2 RNA editing is alterations in the 5HT2CR. The hypothesis to be tested in the present application is that ADAR2 transgenic mice have altered 5HT2CR editing in brain subregions that have been implicated in depression, and hence have a blunted serotonin synaptic function which induces depression-like behavioral changes. Further characterization of depression-related behaviors and regional RNA editing of 5HT2CR in the brain of ADAR2 transgenic mice and their response to specific antidepressant drugs will provide an opportunity to evaluate a potentially valuable animal model of psychological depression and to gain insight into the mechanisms of this form of affective disorder. PUBLIC HEALTH RELEVANCE: The applicant has recently developed a new line of transgenic mouse that may have direct clinical relevance for the treatment of psychological depression. This application focuses on validation of the ADAR2 transgenic mouse as a model of psychological depression and the role of serotonin 2C receptor RNA editing leading to depression. The model may also be useful in examining neuronal substrates or loci involved in depression. Predicting clinical outcomes from a rodent model of psychological depression may further prove to be useful for understanding the efficacy and tolerability of antidepressants.