The H3K9 HISTONE SWITCH; 'LEVELS' IN SCHIZOPHRENIA BLOOD AND BRAIN

描述(申请人提供)：染色质是组蛋白和基因组DNA的复合体，通过限制或允许DNA结合蛋白附着到基因的调控序列来转导环境事件对转录组的影响。H3K9组蛋白双峰开关在将染色质“限制性”(DimH3K9)或“容许性”(AceH3K9)组装到基因组的富含基因的区域中起着关键作用。这一提议的中心假设是，在精神分裂症患者中，染色质趋于一种更严格的状态。这具有直接的临床后果，因为基因组DNA与限制性染色质隔离，转录效率低下，可能解释了突触精神药理学的临床反应不佳的原因，还因为组蛋白共价修饰可以作为小分子药理学的靶点。Ttoto的具体目标将调查以下假设：a)H3K9开关处于不同的限制状态 (B)对活着的患者外周血中H3K9的“血液水平”的测量将发现一个同质样本，该样本的允许状态(AceH3K9)水平较低，该样本将优先对临床上的HDAC抑制剂，如丙戊酸产生反应。染色质结构和功能将在来自哈佛大脑收集的尸检大脑样本和来自三个诊断组的活着患者的循环血单个核细胞(PBMC)中进行检测；i)正常人，ii)精神分裂症(包括首发和慢性)，iii)双相情感障碍。在尸脑中，我们将应用全基因组分子技术(CHIP-SEQ)来调查和分析DimH3K9的分布。对死后大脑进行的CHIP-SEQ实验的数据将揭示这种限制性染色质携带的基因网络，并抑制了mRNA的转录。因此，来自DimH3K9抑制网络的mRNA输出将使用qRT-PCR在不同诊断组之间进行验证和比较。在活体患者中，我们将量化单个核细胞核提取物中的DimH3K9和AceH3K9的“血液水平”；那些AceH3K9水平最低的受试者(因此具有较高的限制性染色质水平)将被随机分成一项对照试验，使用HDAC抑制剂丙戊酸(以加巴喷丁为抗惊厥对照)，以探索能够“放松”染色质的药物的治疗潜力。在这个项目结束时，我们将对两种主要精神障碍中的染色质集合进行调查，并定位于回答几个与临床人群中表观遗传基因调控有关的问题。同样重要的是，我们开始翻译在一个具有重大理论和治疗意义的领域中对活着的临床人群进行的细胞、动物和死后脑研究的发表结果。 与公共健康相关：染色质是调节和解释遗传密码的平台，因此在包括脑神经元在内的任何细胞的功能中都发挥着极其重要的作用。这项研究将扩展基础科学实验室令人兴奋的发现，该实验室强烈暗示染色质异常与精神分裂症疾病过程有关，并试图在活着的患者中研究这些机制。如果精神分裂症与染色质组织的异常有关，这种新的方法将打开一种全新类型的精神药物的大门，即放松染色质结构并允许更有效地工作遗传密码的药物。

DESCRIPTION (provided by applicant): Chromatin is a complex of histone proteins and genomic DNA, and serves to transduce the impact of environmental events on the transcriptome by either restricting or permitting the attachment of DNA binding proteins to the regulatory sequences of a gene. The H3K9 histone bimodal switch is pivotal in assembling either 'restrictive' (DimH3K9) or 'permissive' (AceH3K9) chromatin to gene-rich regions of the genome. The central hypothesis for this proposal is that, in schizophrenia, chromatin equilibrates towards a more restrictive state. This has direct clinical consequences because genomic DNA sequestered with restrictive chromatin, is inefficiently transcribed, may explain the less than optimal clinical response to synaptic psychopharmacology, and also because histone covalent modifications can be targeted with small molecule pharmacology. The specific aims in-toto will investigate the hypotheses: a) the H3K9 switch is differentially in the restrictive state (DimH3K9) in schizophrenia patients in both blood and brain; b) measurement of peripheral 'blood levels' of H3K9 in living patients will identify a homogeneous sample with lower levels of the permissive state (AceH3K9) that will respond preferentially to a clinical HDAC inhibitor such as valproic acid. Chromatin structure and function will be examined in both, postmortem brain samples from the Harvard brain collection, and circulating blood mononuclear cells (PBMC) from living patients obtained from three diagnostic groups; i) normals, ii) schizophrenia (both first episode and chronic), iii) bipolar disorder. In the postmortem brain, we will apply genome-wide molecular techniques (ChIP-seq) to survey and analyze the distribution of DimH3K9. Data from the ChIP-seq experiments on postmortem brain will reveal gene networks that are entrained by this restrictive chromatin and have repressed mRNA transcription. Accordingly, mRNA output from DimH3K9 repressed networks will be verified and compared across diagnostic groups using qRT-PCR. In living patients, we will quantify 'blood levels' of both DimH3K9 and AceH3K9 from nuclear extracts of blood mononuclear cells; those subjects with the lowest levels of AceH3K9 (and thereby possessing higher levels of restrictive chromatin) will be randomized to a controlled trial with the HDAC inhibitor valproic acid (with gabapentin as anticonvulsant control) to explore the therapeutic potential of medications capable of 'relaxing' chromatin. At the end of this project, we would have conducted a survey of chromatin assemblies in two major mental disorders and be positioned to answer several questions relating to epigenetic gene regulation in a clinical population. Equally important we begin the translation of published findings from cell, animal and post-mortem brain investigations into living clinical populations in an area with great theoretical and therapeutic implications. PUBLIC HEALTH RELEVANCE: Chromatin is the platform on which the genetic code is regulated and interpreted, and consequently plays an extremely important role in the functioning of any cell including the brain neuron. This study will extend exciting findings from the basic science laboratory that strongly implicates chromatin abnormalities in the schizophrenia disease process, and attempt to study these mechanisms in living patients. If schizophrenia is associated with abnormalities in chromatin organization, this new approach will open the door to a whole new type of psychiatric medication, i.e., drugs that relax chromatin structure and allow a more efficient working of the genetic code.