Epigenetic Markers in Huntington's disease Brain

描述(申请人提供)：亨廷顿病(HD)是一种致命的常染色体显性遗传性神经退行性疾病，由HD基因中CAG束扩大引起，导致逐渐丧失记忆、认知技能和正常运动。多条研究路线指出，转录失调是HD病理的一个普遍特征，并表明突变蛋白(Htt)改变的组蛋白修饰可能有助于这一过程。然而，到目前为止，还没有关于人类HD脑中组蛋白修饰的全基因组分析。本文提出的研究将新的基因组技术应用于寻找HD脑中的表观遗传学特征，以期深入了解HD的发病机制。我们的建议利用了两个独特的资源：(1)一种新的FACS-CHIP-SEQ方法，我们将应用它来建立和比较HD和对照大脑的神经元的甲基组；以及(2)独特的HD大脑样本，包括一组与CAG重复扩展匹配的样本(重复范围42-44个重复)，但发病年龄相差30岁或更长。对于纹状体和皮质受累的程度，大脑有广泛的神经病理学特征。由于我们发现HD大脑中的组蛋白H3甲基化标记与CD4细胞中的信号高度重叠，我们还比较了HD大脑中看到的改变的表观遗传特征与疾病不同阶段(症状前、早期和晚期HD)的血液样本中的表观遗传特征，因为这可能在HD血液中提供一个新的表观遗传生物标记物。这些生物标记物对于重新调整基因表达的药物治疗的评估具有翻译意义。我们使用FACS-CHIP-SEQ方法在6个HD前额叶皮质样本和11个正常对照中获得了初步数据，这为拟议研究的意义提供了诱人的证据，并表明我们有能力应用这些技术并对结果进行有意义的解释。我们的方法代表了迄今为止关于组蛋白甲基化在HD发病机制中的作用的最全面的分析。无论结果如何，这些研究将为HD发病的分子途径提供关键的新见解，并可能发现HD治疗的新分子靶点。我们提出了在HD血细胞中识别和表征一个独特的组蛋白甲基化生物标记物，从而增加了这一提议的高翻译影响。如果成功，这种生物标记物的识别将极大地促进新的HD疗法的临床试验，并为评估新的药物治疗是否纠正基因表达中断提供了一种新的方法。

DESCRIPTION (provided by applicant): Huntington's disease (HD) is a fatal, autosomal dominant neurodegenerative disorder caused by an expanded CAG tract in the HD gene that results in gradual loss of memory, cognitive skills and normal movements. Multiple lines of research point to dysregulated transcription as a prevailing feature of HD pathology and suggest that altered histone modification by the mutant protein (Htt) may contribute to this process. However, thus far there has been no genome-wide analysis of histone modifications in human HD brain. The studies proposed here apply novel genomic technology to the search for epigenetic signatures in HD brains with the goal of gaining insight into HD pathogenesis. Our proposal capitalizes on two unique resources: (1) a novel FACS-ChIP-seq method which we will apply to establish and compare the methylomes of neurons from HD and control brains; and (2) a unique sample of HD brains, including a set matched for CAG repeat expansion (range 42-44 repeats) but onset ages differing by 30 years or more. The brains have been extensively neuropathologically characterized for degree of both striatal and cortical involvement. Since we found that histone H3 methylation markings in HD brains overlap highly with the signal in CD4+ cells, we are also comparing the altered epigenetic signature seen in HD brain to that in blood samples at varying stages of disease (presymptomatic, early and advanced HD) as this may offer a novel epigenetic biomarker in HD blood. Such biomarkers are of translational significance for the evaluation of drug treatments to realign the disrupted gene expression. We have preliminary data using the FACS-ChIP-Seq method in six HD prefrontal cortex samples and eleven normal controls, which provides tantalizing evidence for the significance of the proposed studies and demonstrates our capabilities to apply the techniques and to meaningfully interpret the findings. Our approach represents the most comprehensive analysis to date addressing the role of histone methylation in HD pathogenesis. Regardless of outcome, these studies will provide critical new insights into the molecular pathways of HD pathogenesis and may also uncover novel molecular targets for HD treatment. The high translational impact of this proposal is increased by our proposal to identify and characterize a unique histone methylation biomarker in HD blood cells. If successful, identification of such a biomarker will greatly facilitate clinical trials for novel HD therapies and offers a novel method to evaluate whether new drug treatments rectify disrupted gene expression.