Modeling uniquely human developmental gene regulatory networks using humanized mice

身体适应是人类进化的标志。我们四肢的形态变化使我们能够 使用复杂的工具和直立行走，人类大脑皮层的扩张是我们的起源， 高级认知能力这些特征最终被编码在人类进化过程中出现的基因变化中， 进化，并在发育过程中改变分子和细胞过程。这个目标 2010年开始的一个正在进行的研究项目是确定这些变化在基因组中的位置， 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， 在人类中编码新的功能。第一个是人类加速区（HAR），其中许多编码 在物种间高度保守但显示多个人类特异性序列的转录增强子 变化第二类元件是人类增益增强子（Human Gain Enhancers，HGE），其是转录的。 基于表观遗传标记的比较，在发育中的人类组织中显示出增加的活性的增强子 与人、恒河猴和小鼠中的增强子活性相关。这些发现揭示了 基因调控在人类独特形态的进化中发挥了核心作用， 为人类发展进化的实验建模提供了手段。在这个融资周期中，我们将 利用人源化小鼠模型研究了HACNS1的生物学功能，我们首次鉴定了它， 已知HAR编码人类特异性调节活性。HACNS1在细胞内保持其人类特异性活性， 发育中的小鼠肢体，并改变了附近转录因子Gbx2在发育中的表达。 胚胎发育我们假设，HACNS1是在一个更大的人类特异性网络中起作用的。 改变发展的监管变化。使用HACNS1小鼠模型和我们的 作为切入点，我们将确定转录和 在单细胞分辨率下，HACNS1下游的调控变化，模型额外的人类特异性 可能与由HACNS 1驱动的监管变化相互作用的监管功能，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.