Modeling uniquely human developmental gene regulatory networks using humanized mice

身体适应是人类进化的一个标志。我们四肢的形态变化使我们能够 并使用复杂的工具和直立行走，而人类大脑皮层的扩张是我们 高级认知能力。这些特征最终编码在人类进化过程中产生的基因变化中 进化，并在发育过程中改变分子和细胞过程。这样做的目的是 正在进行的研究项目始于2010年，目的是确定这些变化在基因组中的位置，以及 以了解它们的生物学功能。我们的努力集中在两类基因调控元件上，它们可能 对人类的新功能进行编码。第一个是人类加速区(HARs)，其中许多编码 转录增强子在物种间高度保守，但显示多个人类特有的序列 改变。第二类元素是人类增益增强剂(HGE)，它是转录的 根据表观遗传标记的比较显示在发育中的人体组织中活性增加的增强剂 与人类、恒河猴和小鼠的增强子活性有关。这些发现揭示了 在发育过程中，基因调控在独特的人类形态和 提供实验模拟人类发展演变的手段。在这个资金周期中，我们将 利用人源化小鼠模型研究HACNS1的生物学功能，这是我们首次鉴定的 已知的HAR编码人类特有的调节活动。HACNS1保持其人类特有的活性 并改变邻近转录因子Gbx2在小鼠肢体中的表达 发育中的胚胎。我们假设HACNS1是在一个更大的人类特异性网络中起作用的 调整开发的监管变化。使用HACNS1小鼠模型和我们的地图 以肢体中人类特有的调节功能为切入点，我们将识别转录和 HACNS1下游单细胞分辨率的调控变化，模型额外的人类特异性 监管职能，可以与HACNS1驱动的监管变化相互作用，并确定 这些变化如何影响肢体的发育。

Physical adaptation is a hallmark of human evolution. Morphological changes in our limbs allowed us to make and use sophisticated tools and to walk upright, and the expansion of the human cortex is the origin of our advanced cognitive abilities. These traits are ultimately encoded in genetic changes that arose during human evolution, and which acted to alter molecular and cellular processes during development. The goal of this ongoing research project, which began in 2010, is to determine where in the genome those changes reside and to understand their biological functions. Our efforts focus on two classes of gene regulatory elements that may encode novel functions in humans. The first are Human Accelerated Regions (HARs), many of which encode transcriptional enhancers that are highly conserved across species but show multiple human-specific sequence changes. The second class of elements are Human Gain Enhancers (HGEs), which are transcriptional enhancers that show increased activity in developing human tissues based on comparisons of epigenetic marks associated with enhancer activity in human, rhesus macaque and mouse. These discoveries reveal that changes in developmental gene regulation played a central role in the evolution of uniquely human morphology and provide the means to experimentally model the evolution of human development. In this funding cycle, we will use humanized mouse models to study the biological function of HACNS1, which we identified as the first known HAR to encode human-specific regulatory activity. HACNS1 maintains its human-specific activity in the developing mouse limb and alters the expression of the nearby transcription factor Gbx2 in the developing embryo. We hypothesize that HACNS1 is acting within a larger network of human-specific regulatory changes that modified development. Using the HACNS1 mouse model and our maps of human-specific regulatory functions in the limb as entry points, we will identify transcriptional and regulatory changes downstream of HACNS1 at single-cell resolution, model additional human-specific regulatory functions that may interact with the regulatory changes driven by HACNS1, and determine how these changes influence the development of the limb.