Haematopoietic stem cells do not asymmetrically segregate chromosomes or retain BrdU
Haematopoietic stem cells do not asymmetrically segregate chromosomes or retain BrdU
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DOI：
10.1038/nature06115
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发表时间：
2007-09-13
期刊：
影响因子：
64.8
通讯作者：
Morrison, Sean J.
中科院分区：
文献类型：
--
作者：
Kiel, Mark J.;He, Shenghui;Morrison, Sean J.
干细胞被建议在自我更新分裂过程中不对称地分离染色体，以便较老的(不朽的)DNA链保留在子代干细胞中，而新合成的链分离到分化细胞(1-6)。干细胞也被建议保留DNA标记，如5-溴-2-脱氧尿苷(BrdU)，因为它们不对称地分离染色体，或者因为它们分裂缓慢(5，7-9)。然而，BrdU标记保留细胞中干细胞的纯度还没有在任何组织中被记录下来，“永生链假说”也没有在具有明确干细胞标记的系统中进行测试。在这里，我们在造血干细胞(HSCs)中测试了这些假设，使用特征良好的标记可以高度纯化HSCs。给新生小鼠、用环磷酰胺和粒细胞集落刺激因子处理的小鼠和正常成年小鼠注射BrdU 4~10天，然后70天不用BrdU。在每个病例中，保留BrdU的HSC不到6%，保留BrdU的所有造血细胞中不到0.5%是HSCs，这表明BrdU作为HSC标志物的特异性和敏感性都很差。5-氯-2-脱氧尿苷和5-碘-2-脱氧尿苷的连续给药表明，所有的HSC都是随机分离的。分离培养中的单个HSCs没有发现标记的不对称分离。因此，不能在BrdU标记保留的基础上识别HSCs，并且在分裂过程中不保留较老的DNA链，这表明这些不是干细胞的一般特性。
Stem cells are proposed to segregate chromosomes asymmetrically during self-renewing divisions so that older ('immortal') DNA strands are retained in daughter stem cells whereas newly synthesized strands segregate to differentiating cells(1-6). Stem cells are also proposed to retain DNA labels, such as 5-bromo-2-deoxyuridine (BrdU), either because they segregate chromosomes asymmetrically or because they divide slowly(5,7-9). However, the purity of stem cells among BrdU-label-retaining cells has not been documented in any tissue, and the 'immortal strand hypothesis' has not been tested in a system with definitive stem cell markers. Here we tested these hypotheses in haematopoietic stem cells (HSCs), which can be highly purified using well characterized markers. We administered BrdU to newborn mice, mice treated with cyclophosphamide and granulocyte colony-stimulating factor, and normal adult mice for 4 to 10 days, followed by 70 days without BrdU. In each case, less than 6% of HSCs retained BrdU and less than 0.5% of all BrdU-retaining haematopoietic cells were HSCs, revealing that BrdU has poor specificity and poor sensitivity as an HSC marker. Sequential administration of 5-chloro-2-deoxyuridine and 5-iodo-2-deoxyuridine indicated that all HSCs segregate their chromosomes randomly. Division of individual HSCs in culture revealed no asymmetric segregation of the label. Thus, HSCs cannot be identified on the basis of BrdU-label retention and do not retain older DNA strands during division, indicating that these are not general properties of stem cells.