Our bodies are made up of over 250 specific cell types, and all initially arise from stem cells during embryonic development. Stem cells have two characteristics that make them unique: (1) they are pluripotent, meaning that they can differentiate into all cell types of the body, and (2) they are capable of self-renewal to generate more of themselves and are thus able to populate an organism. Human pluripotent stem cells were first isolated from human embryos twenty years ago ( Thomson et al., 1998 ) and more recently, technology to reprogram somatic cells, such as skin and blood, to induced pluripotent stem cells has emerged ( Park et al., 2008 ; Takahashi et al., 2007 ; Yu et al., 2007 ). Induced pluripotent stem cells, or iPSCs, are particularly valuable as disease specific iPSCs can be generated from individuals with specific genetic mutations diseases. Researchers have harnessed the power of stem cells to understand many aspects of developmental biology in model organisms (e.g. worms, mice) and more recently, in humans. Human stem cells in culture recapitulate development. For example, formation of the brain occurs prenatally and follows a specific pattern of timing and cell generation. Human stem cells in the culture dish follow a similar pattern when exposed to developmental cues and can thus be used to understand aspects of prenatal human brain development that are not accessible by other means. Disease-specific iPSCs are a valuable tool to model neural development in specific neurodevelopmental disorders like Down syndrome. Down syndrome is a classic developmental disorder; mistakes that are made during development of a particular organ system result in the characteristics of the disorder. In the brain, mistakes during prenatal brain development lead to intellectual disability. Trisomy 21 (Ts21) iPSCs generated from somatic cells of Down syndrome individuals may enable us to understand the mistakes made during Down syndrome brain development.

中文翻译：

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人类干细胞对唐氏综合症大脑发育和功能的认识不断提高。

我们的身体由250多种特定的细胞类型组成，所有这些细胞最初都是在胚胎发育过程中源自干细胞。干细胞具有使其具有独特性的两个特征：（1）它们具有多能性，这意味着它们可以分化为人体的所有细胞类型；（2）它们具有自我更新的能力，可以产生更多的自身，因此能够填充生物体。人类多能干细胞是二十年前从人类胚胎中分离出来的（Thomson等，1998），最近，出现了将皮肤和血液等体细胞重编程为诱导性多能干细胞的技术（Park等， 2008； Takahashi等人，2007； Yu等人，2007）。诱导多能干细胞或iPSC，疾病特异性iPSC可以从患有特定基因突变疾病的个体中产生，因此具有特别的价值。研究人员已经利用干细胞的力量来了解模型生物（例如蠕虫，小鼠）以及人类最近的发育生物学的许多方面。培养中的人类干细胞概括了发育过程。例如，大脑的形成发生在产前，并遵循特定的时间安排和细胞生成模式。当暴露于发育线索时，培养皿中的人类干细胞遵循相似的模式，因此可用于了解其他方式无法访问的产前人类大脑发育的各个方面。特定于疾病的iPSC是在特定的神经发育障碍（如唐氏综合症）中为神经发育建模的有价值的工具。唐氏综合症是一种典型的发育障碍。在特定器官系统发育过程中犯的错误会导致疾病的特征。在大脑中，产前大脑发育过程中的错误会导致智力残疾。由唐氏综合症个体的体细胞产生的21三体（Ts21）iPSC可能使我们能够理解唐氏综合症大脑发育过程中所犯的错误。