Using human IPS cells to study fate, function and neurodegenerative disease

人诱导多能干细胞（iPSC），具有产生自体患者源性 细胞，为研究和治疗一系列毁灭性疾病，包括 帕金森氏病（PD）和肌萎缩侧索硬化症（ALS），仅举几例。的一个主要 阻碍这种强大技术向临床转化的障碍是两者的异质性。 在iPSC移植物中产生所需和不需要的细胞类型，即使在细胞已经定向向下生长之后， 特定的分化途径。同样，在培养中，处理后产生多种细胞类型 与特定谱系的鸡尾酒。这些现实，加上目前缺乏合适的细胞， 用于选择特定的所需细胞类型的表面标记，已经显著地影响了该领域， 阻碍了我们开发细胞替代疗法或在培养皿中准确模拟疾病的能力。 对观察到的细胞异质性的一个合理解释是， 多能细胞有时在遇到谱系后自发地启动分化过程， 在文化中指定线索，从而排除他们随后的定向分化的外源性 添加差异化鸡尾酒。目前，还没有可靠的方法来知道iPSC是否已经开始 自发分化。然而，在我们上一个资助周期中有一个令人兴奋的新发现 这表明，DNA复制后不久染色质的表观遗传状态是一个可靠的， 干细胞分化状态的早期指标。我们的研究结果表明， 如果染色质可以保持封闭，则统一地指导所有iPSC朝向特定细胞命运的分化 直至与外源性命运特异性分化因子一起孵育。如果这些见解表明 更普遍的原则，那么应该有可能产生纯神经祖细胞群体 (NPs)不同的亚型，可以产生各种神经元的同质群体进行研究 在培养物和多种疾病的动物模型中。考虑到这些目标，我们的具体目标是 建议是：1）评估在向运动神经元表型转化期间的染色质状态; 2） 产生纯的中脑多巴胺（mDA）和运动神经元和神经元， 在培养物中表征表型和突触功能，以及3）进一步确定是否 均一的mDA定向的NP/神经元可以在培养皿中准确地模拟PD，并用于 移植来治疗PD大鼠模型。

Human induced pluripotent stem cells (iPSCs), with their potential to generate autologous patient-derived cells, hold great promise for the study and treatment of a host of devastating diseases, including Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS), to name a few. One of the major obstacles slowing the translation of this powerful technology to the clinic is the heterogeneity of both desired and unwanted cell types generated in grafts of iPSCs, even after cells have been directed down specific differentiation pathways. Similarly in culture, a multitude of cell types are generated after treatment of iPSCs with lineage-specifying cocktails. These realities, combined with the current lack of suitable cell surface markers for the selection of specific desired cell types, has significantly impacted the field, hampering our ability to develop cell replacement therapies or to accurately model diseases in the dish. One plausible explanation for the observed cell heterogeneity is that presumptive undifferentiated pluripotent cells sometimes spontaneously initiate the process of differentiation after encountering lineage- specifying cues in culture, thereby precluding their subsequent directed differentiation by exogenously added differentiation cocktails. Currently, there are no assured ways to know if iPSCs have begun to spontaneously differentiate. However, an exciting new discovery made during our previous grant cycle suggests that the epigenetic state of chromatin shortly after DNA replication serves as a reliable and very early indicator of the state of differentiation of a stem cell. Our results suggest that it may be possible to uniformly direct the differentiation of all iPSCs toward a specific cell fate if chromatin can be kept closed until incubation with exogenous fate-specifying differentiation factors. If these insights are indicative of a more generalized principle, then it should be possible to generate pure populations of neural progenitors (NPs) of different subtypes which can give rise to homogeneous populations of various neurons for studies in culture and in animal models of multiple diseases. With these goals in mind, our Specific Aims for this proposal are: 1) to assess chromatin status during commitment to a motor neuron phenotype; 2) to generate pure populations of midbrain dopamine (mDA) and motor NPs and neurons which will be characterized for phenotype and synaptic function in culture and 3) to further determine whether homogeneous mDA-committed NPs/neurons can accurately model PD in the dish and be used in transplants to therapeutically treat PD rat models.