Identifying enhancers with human-specific developmental functions

 描述（由申请人提供）：与其他灵长类动物相比，人类具有独特的生物学特征。其中最重要的是更大更复杂的大脑皮层，以及四肢的形态变化，使人类能够使用复杂的工具和直立行走。这些物理创新的进化一直被认为涉及改变发育中基因调控的序列变化。然而，这些变化的位置现在才开始被揭示，它们对基因表达和发育的影响仍然未知。该研究项目于2010年启动，其目标是确定具有人类特定发育活动的调控元件，并确定其生物学影响。在目前的资助期内，我们专注于使用两种互补策略绘制可能编码独特的人类启动子或增强子功能的位点。第一个是对保守的非编码序列进行实验分析，这些序列显示出人类的加速进化，我们和其他小组已经表明，这些序列包括具有人类特异性活性的发育增强子。第二个是对人类、恒河猴和小鼠的肢体和皮层发育进行比较表观遗传分析，以直接鉴定在人类中获得活性的启动子和增强子。表现出人类特异性进化加速和基于表观遗传标记的活性增加的序列是编码具有潜在大的生物学效应的新型调控功能的主要候选者。我们在这一更新的优先事项是生成和研究人类加速区域的人源化小鼠模型，这些模型在发育中的人类肢体或皮层中显示表观遗传增益。我们将利用CRISPR/Cas9基因组编辑技术，通过在单细胞小鼠胚胎中进行基因打靶，快速生成转基因小鼠。然后，我们将在这些模型中对胚胎发育进行全基因组分子分析，以确定基因表达和调控的全局变化。在这些研究结果的指导下，我们将对人源化小鼠的肢体和皮层发育进行有针对性的表型分析，以确定由人类特异性调节变化改变的生物过程。

 DESCRIPTION (provided by applicant): Humans possess unique biological features compared to other primates. Among the most important of these are a larger and more complex cerebral cortex, and morphological changes in the limbs that allow humans to use sophisticated tools and walk upright. The evolution of these physical innovations has long been thought to involve sequence changes that altered gene regulation in development. However, the locations of such changes are only now beginning to be revealed, and their effects on gene expression and development remain unknown. The goal of this research project, which was initiated in 2010, is to identify regulatory elements with human-specific developmental activities and determine their biological impact. In the current funding period, we have focused on mapping sites likely to encode uniquely human promoter or enhancer functions using two complementary strategies. The first is experimental analysis of conserved noncoding sequences that show accelerated evolution in humans, which we and other groups have shown include developmental enhancers with human-specific activities. The second is comparative epigenetic analysis of limb and cortex development in human, rhesus macaque and mouse, to directly identify promoters and enhancers that have gained activity in humans. Sequences that exhibit both human-specific evolutionary acceleration and increased activity based on epigenetic marks are prime candidates for encoding novel regulatory functions with potentially large biological effects. Our priority in this renewal is to generate and study humanized mouse models for human accelerated regions that show epigenetic gains in the developing human limb or cortex. We will use CRISPR/Cas9 genome editing technology to rapidly generate genetically modified mice by gene targeting in single cell mouse embryos. We will then conduct genome-wide molecular analyses of embryonic development in these models to identify global changes in gene expression and regulation. Guided by the results of these studies, we will carry out targeted phenotypic analysis of limb and cortex development in humanized mice to identify biological processes altered by human-specific regulatory changes.