Regulation of response to chronic antidepressant treatment by MeCP2

描述(申请人提供)：大多数目前可用的抗抑郁药物迅速改变大脑中的神经传递，但需要长期服用才能影响情绪。这些观察表明，药物诱导的神经传递变化下游的缓慢生物过程可能是对这些抗抑郁药物的行为反应所必需的，这些变化被认为包括基因转录的变化。这项建议的目的是促进对调节慢性抗抑郁药物治疗行为反应的基本大脑机制的理解。我们发现，甲基DNA结合的染色质调节蛋白MeCP2是抗抑郁药物调节的靶点，MeCP2的突变改变了小鼠对慢性抗抑郁药物治疗的行为反应。具体地说，我们发现，在中枢神经系统中增加5-羟色胺和多巴胺神经传递的药物，包括抗抑郁药西酞普兰，在选定的中枢神经系统神经元中诱导Ser421处MeCP2(PMeCP2)的磷酸化。为了测试pMeCP2与抑郁样行为和抗抑郁反应的功能相关性，我们获得了一种小鼠品系，该品系携带Ser421Ala突变敲击到MeCP2基因，使MeCP2蛋白在该位置不可磷酸化。我们已经在社会失败应激范式中测试了这种突变对这些小鼠的抑郁样行为和对慢性抗抑郁药物治疗的反应的后果。我们发现，MeCP2敲门小鼠和它们的野生型小鼠在失败后表现出相似的社交回避水平。然而，虽然慢性丙咪嗪治疗挽救了野生型小鼠的社交互动，但这种药物治疗未能改善敲门小鼠的社交回避。在这些和其他初步数据的基础上，我们假设MeCP2在Ser421处的磷酸化是慢性抗抑郁药物治疗的至少一个行为反应子集所必需的。这是一个全新的假设。此前没有研究证实MeCP2在抑郁样行为或抗抑郁药物治疗反应中的作用。我们的发现可以通过将染色质的这种重要的表观遗传调节因子与大脑长期服用抗抑郁药物的作用联系起来，对理解抑郁样行为和对抗抑郁药物的反应的大脑过程产生重大影响。我们提出的假设有以下两个具体目标：1)分析MeCP2Ki小鼠的抑郁样行为和抗抑郁反应；2)识别MeCP2依赖的抑郁样行为的神经回路。

DESCRIPTION (provided by applicant): Most currently available antidepressant drugs rapidly alter neurotransmission in the brain yet require chronic administration to affect mood. These observations suggest that slow biological processes downstream of drug- induced changes in neurotransmission, which are thought to include changes in gene transcription, are likely to be required for the behavioral response to these antidepressant drugs. The goal of this proposal is to advance understanding of the basic brain mechanisms that regulate behavioral responses to chronic antidepressant treatment. We have discovered that the methyl-DNA binding chromatin regulatory protein MeCP2 is a target of regulation by antidepressants, and that mutations in MeCP2 alter behavioral responses to chronic antidepressant treatment in mice. Specifically we find that administration of drugs that enhance serotonin and dopamine neurotransmission in the CNS, including the antidepressant citalopram, induces phosphorylation of MeCP2 at Ser421 (pMeCP2) in selected CNS neurons. To test the functional relevance of pMeCP2 for depressive-like behaviors and antidepressant responses we obtained a strain of mice that bear a germline Ser421Ala mutation knocked into the Mecp2 gene that renders MeCP2 protein nonphosphorylatable at this site. We have tested the consequence of this mutation on depressive-like behaviors and response to chronic antidepressant treatment in these mice in the social defeat stress paradigm. We find that both MeCP2 knockin mice and their wildtype littermates show similar levels of social avoidance following defeat. However whereas chronic imipramine treatment rescues social interaction in the wildtype mice, this drug treatment fails to ameliorate social avoidance in the knockin mice. On the basis of these and other preliminary data we hypothesize that phosphorylation of MeCP2 at Ser421 is required for at least a subset of behavioral responses to chronic antidepressant treatment. This is a completely novel hypothesis. No prior studies have examined a role for MeCP2 in depressive-like behaviors or response to antidepressant treatment. Our findings could have a substantial impact on the understanding of brain processes that underlie depressive-like behaviors and response to antidepressants by linking this important epigenetic regulator of chromatin to the actions of chronic antidepressant administration on the brain. We propose to address our hypothesis with the following two specific aims: 1) To analyze depressive-like behaviors and antidepressant responses in MeCP2 KI mice and 2) To identify neural circuits that underlie MeCP2-dependent effects on depressive-like behaviors.