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Abstract：
Hematopoietic stem cells (HSCs) are a population of tissue-specific stem cells that reside in the bone marrow of adult mammals, where they self-renew and continuously regenerate the adult hematopoietic lineages over the life of the individual. Prominence as a stem cell model and clinical usefulness have driven interest in understanding the physiologic processes that lead to the specification of HSCs during embryonic development. High-efficiency directed differentiation of HSCs by the instruction of defined progenitor cells using sequentially defined instructive molecules and conditions remains impossible, indicating that comprehensive knowledge of the complete set of precursor intermediate identities and required inductive inputs remains incompletely understood. Recently, interest in the molecular and cellular microenvironment where HSCs are specified from endothelial precursors-the \"specification niche\"-has increased. Here we review recent progress in understanding these niche spaces across vertebrate phyla, as well as how a better characterization of the origin and molecular phenotypes of the niche cell populations has helped inform and complicate previous understanding of signaling required for HSC emergence and maturation.
摘要：
造血干细胞(HSC)是存在于成年哺乳动物的骨髓中的组织特异性干细胞群,在那里它们在个体的一生中自我更新并连续再生成年造血谱系。作为干细胞模型和临床有用性的重要性促使人们对理解导致胚胎发育过程中HSC特化的生理过程感兴趣。通过使用顺序定义的指导性分子和条件的定义的祖细胞的指令，HSC的高效定向分化仍然是不可能的。表明对前体中间身份和所需感应输入的完整集合的全面知识仍未完全理解。最近,对从内皮前体指定HSC的分子和细胞微环境的兴趣增加了。在这里，我们回顾了在理解脊椎动物门的这些生态位空间方面的最新进展，以及对生态位细胞群体的起源和分子表型的更好表征如何帮助告知和复杂先前对HSC出现和成熟所需信号传导的理解。
