The Evolution of DNA methylation patterns in neurons of the frontal cortex of humans and non-human primates

在灵长类动物的进化史上，在所有只属于人属的特征中，最显著的特征之一就是大脑的大小。与脑化类似，沟通能力的进化似乎在语言上达到顶峰，这是人类独有的，也是认知能力的关键组成部分。语言既是大脑加速的驱动力，也是大脑加速的结果。因此，为了理解大脑进化背后的机制，有必要了解人类特定交流能力的进化根源以及生物和分子基础，特别是语言，这个问题最好通过人类与灵长类动物的比较来解决。除了语言学家之间关于人类语言能力的争论之外，人们似乎一致认为，一个关键特征是评估他人精神状态的能力。但是这种基本能力在自闭症谱系障碍（ASD）中受到严重干扰。从疾病的遗传原因推断基因的功能是一种常见的研究方法，因此注意到ASD中的突出基因与沟通或语言基因（如CNTNAP2）一样被认为是不足为奇的。鉴于黑猩猩和人类的DNA序列高度相似，在过去十年中对这两个物种的基因表达进行的比较表明，基因调控对灵长类动物进化的影响可能比DNA序列更大。到目前为止，只有少数研究集中在灵长类动物特异性DNA甲基化模式的机制上。然而，这些研究大多使用大块组织来研究人类和非人类灵长类动物的大脑，而不是像神经元或神经胶质细胞这样的单细胞类型。我们认为，在人类大脑进化过程中，神经元DNA甲基化模式在人类和灵长类动物之间发展不同。为了解决这个问题，我们希望应用激光捕获显微解剖（LCM）从大块脑组织中分离神经元和其他细胞类型。结合下游技术，如基于下一代测序（NGS）的RNAseq和减少代表性亚硫酸氢盐测序（RRBS），以及焦磷酸测序，概述的策略将使我们能够评估物种特异性甲基化模式及其对全基因组基因调控和选定候选基因的影响。该研究项目将为人类交流/语言以及大脑进化的分子进化提供见解，并可能为ASD和相关语言障碍的治疗干预开辟途径。

In the evolutionary history of primates one of the most distinctive features among all traits attributed exclusively to the genus homo is brain size. Similar to enzephalization, communication abilities seem to evolve peaking in language which is uniquely assigned to humans and a key component of cognitive abilities. Language is suggested to be both a driving force as well as an outcome of brain acceleration. In order to understand the mechanisms behind brain evolution it is thus essential to understand the evolutionary roots as well as the biological and molecular basis of human specific communication abilities, in particular language, an issue best to be addressed through human-primate comparisons. Apart from the ongoing debates among linguists considering the faculty of language of human language, there seems to be a certain agreement that one key feature is the ability to assess mental states of other individuals. But particularly this essential competence is severely interfered with autism spectrum disorders (ASD). Inference from a genetic cause of a disease to the function of a gene is a common research approach, thus it is not surprising to note that prominent genes in ASD are as well considered as communication or language genes like for example CNTNAP2. Given the high similarity between the chimpanzee and human DNA sequences, comparisons of gene expression in these two species in the last decade indicated that gene regulation might have had a bigger impact on primate evolution than DNA sequence. Up to now only a minority of studies focussed on mechanisms underlying primate specific DNA methylation patterns. However, the most of these studies used bulk tissue for research on human and non-human primate brains instead of single cell types like neurons or glia cells. We suggest that during human brain evolution neuronal DNA methylation patterns developed differently between humans and primates.In order to adress this issue we want to apply laser captured microdissection (LCM) for the separation of neurons and other cell types from bulk brain tissue. Together with downstream technologies like Next Generation Sequencing (NGS)-based RNAseq and Reduced Representative Bisulfite Sequencing (RRBS), and Pyrosequencing, the outlined strategies will enable us to assess species specific methylation patterns as well as their impact on genomewide gene regulation and of selected candidate genes. This research project will provide insights into the molecular evolution of human communication/language as well as brain evolution and potentially can open up avenues for therapeutic interventions of ASD and associated language disorders.