Identification of an Epigenetic Risk Marker for PTSD

描述（由申请人提供）：该资助响应NIH挑战08-MH-103：理解精神障碍的基因组风险结构。该应用程序建立在最近动物和人类关于表观遗传机制介导“糖皮质激素编程”的数据基础上，以解决关于早期经历如何增加创伤后应激障碍（PTSD）生物风险的知识鸿沟。知识的差距将通过检查糖皮质激素受体（GR）基因的胞嘧啶甲基化来解决。研究与PTSD风险相关的表观遗传修饰是一个重要的科学前沿。创伤后应激障碍仅在创伤暴露者中发生，但其终生患病率为10-14%。母亲创伤后应激障碍已被确定为第二代后代创伤后应激障碍的危险因素（F2），允许检查与该危险因素相关的生物学机制。GR基因是研究的重点，因为在患有母亲PTSD的F2和其他PTSD样本中已经证实了反映GR反应性增强的改变。胞嘧啶甲基化、GR基因表达和与PTSD风险相关的神经内分泌测量（GR敏感性、负反馈抑制、基础皮质醇水平和代谢）之间的关系将在120f2大屠杀幸存者（根据母亲和父亲是否存在PTSD分组）和30名父母没有大屠杀暴露或PTSD的受试者中进行研究。由于糖皮质激素编程也被认为是一种机制，通过这种机制，（在子宫内）母亲的压力增加了其成年后代随后发展为代谢综合征（MetS）的风险，并且最近的数据将PTSD与MetS的发展及其后果联系起来，因此也将获得MetS的数据。这个项目可以在两年内完成，因为我们可以从以前研究过的大屠杀F2中招募同意重新联系的人。胞嘧啶甲基化将使用由Michael Meaney博士开发的聚合酶链反应（PCR）引物进行量化，该引物选择性地扩增GR基因相关区域的变异，用于人淋巴细胞中DNA甲基化和mRNA剪接变异分析。Meaney博士的研究小组已经证实，人类GR基因的组织结构与大鼠的GR非常相似。我们的主要假设是，与父系创伤后应激障碍相比，母系创伤后应激障碍患者的F2中胞嘧啶甲基化程度更高。通径分析模型将检验这种表观遗传修饰对与PTSD风险相关的神经内分泌和代谢后果的贡献，并结合早期生活经历的其他相关方面（父母症状、童年虐待和忽视、父母照顾和过度保护）来评估它们的贡献。这项工作的创新之处是，试图使用一种自然的代际“模型系统”来检验表观遗传机制在PTSD和相关健康风险的传播脆弱性中的作用，并确定它们与其他环境因素的关系。这一结果对发现有PTSD风险的人有意义，但也可能为预防和早期治疗指明新的目标。患有创伤后应激障碍（PTSD）的母亲的成年子女患PTSD的风险增加，而且他们对应激激素皮质醇的反应也发生了变化，这似乎反映了早期发育的影响，可能是由于母亲的压力效应。在这项研究中，我们调查了这些后代的生物学变化是否反映了一种持久的表观遗传修饰，这种修饰是由早期母亲的行为引起的，这种行为导致皮质醇系统的“重新校准”，从而增加了随后发生创伤后应激障碍和其他可能的健康后果的风险。如果观察到这些变化，这项研究将产生早期（即创伤前）生物标志物，最终可用于在暴露于创伤之前或之后立即筛查PTSD风险增加的人。

DESCRIPTION (provided by applicant): This grant responds to NIH Challenge 08-MH-103: Understanding the Genomic Risk Architecture of Mental Disorders. This application builds on recent animal and human data on epigenetic mechanisms mediating 'glucocorticoid programming' to address a critical gap in knowledge about how early experience confers increased biological risk for post-traumatic stress disorder (PTSD). The gap in knowledge will be addressed by examining cytosine methylation of the glucocorticoid receptor (GR) gene. The study of epigenetic modifications in relation to PTSD risk represents an important scientific frontier. PTSD occurs in only a proportion of those exposed to trauma, but has a population lifetime prevalence of 10-14%. Maternal PTSD has been identified as a risk factor for PTSD in 2nd generation offspring (F2) allowing examination of biological mechanisms in association with this risk factor. The GR gene is the focus of investigation because alterations reflecting enhanced GR responsiveness have been demonstrated in F2 with maternal PTSD, and in other PTSD samples.The relationships among cytosine methylation, GR gene expression, and neuroendocrine measures associated with PTSD risk (GR sensitivity, negative feedback inhibition, basal cortisol level and metabolism) will be examined in 120 F2 of Holocaust survivors (grouped by presence or absence of maternal and paternal PTSD) and in 30 subjects with no parental Holocaust exposure or PTSD. Since glucocorticoid programming has also been implicated as a mechanism through which [in utero] maternal stress increases risk for the subsequent development of metabolic syndrome (MetS) in their adult offspring, and recent data have linked PTSD to the development of MetS and its consequences, data on MetS will also be obtained. This project can be accomplished in two years because we can recruit from previously studied Holocaust F2 that agreed to be recontacted. Cytosine methylation will be quantified using polymerase chain reaction (PCR) primers developed by Michael Meaney, Ph.D. that selectively amplify variations in the relevant region of the GR gene for DNA methylation and splice variant analysis of mRNA in the human lymphocyte. Dr. Meaney's group has confirmed that the organization of the human GR gene closely resembles the rat GR. Our primary hypothesis is that cytosine methylation will be greater in F2 with maternal than paternal PTSD. A path analysis model will examine the contribution of this epigenetic modification to neuroendocrine and metabolic consequences associated with PTSD risk, incorporating other relevant aspects of early life experience (parental symptoms, childhood abuse and neglect, parental care and overprotection) to assess their contribution. This work is innovative in attempting to use a naturalistic intergenerational 'model system' to examine the role for an epigenetic mechanism in transmitted vulnerability for PTSD and associated health risks, and determine their relationship to other environmental contributors. The results have implications for detecting persons at risk for PTSD, but may also point to novel targets for prophylaxis and early treatment. Adult children of mothers with post traumatic stress disorder (PTSD) are at increased risk for PTSD, and also show changes in their responsiveness to the stress hormone cortisol that appear to reflect early developmental influences, possibly resulting from maternal stress effects. In this grant we investigate whether the biological changes in these offspring reflect an enduring epigenetic modification, induced by early maternal behavior that resulted in 'recalibrating' the cortisol system in a manner that increases risk for subsequent PTSD and possibly other health consequences. If such changes are observed, this research will yield an early (i.e., pretraumatic) biologic marker that can ultimately be used in screening persons at increased risk for PTSD either before or immediately after they are exposed to trauma.