Isoform-specific potentiation of stem and progenitor cell engraftment by AML1/RUNX1.
Isoform-specific potentiation of stem and progenitor cell engraftment by AML1/RUNX1.
复制标题
AML1/RUNX1对茎和祖细胞植入的同工型特异性增强。
DOI：
10.1371/journal.pmed.0040172
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发表时间：
2007-05
期刊：
影响因子：
15.8
通讯作者：
Enver T
中科院分区：
文献类型：
--
作者：
Tsuzuki S;Hong D;Gupta R;Matsuo K;Seto M;Enver T
AML1/RUNX1是白血病中最常见的突变基因，是造血干细胞和祖细胞正常生物学的核心。然而，不同AML1亚型在这些原始区室中的作用尚不清楚。在这里，我们研究改变AML1亚型的相对表达是否会影响细胞自我更新和分化之间的平衡，在体外和体内。人类AML1a异构体编码一个截断的分子，具有dna结合能力，但没有转激活能力。我们使用基于逆转录病毒的方法将AML1a转导到从小鼠分离的原始造血细胞中。我们观察到，强制AML1a表达增加了小鼠长期重建干细胞的竞争性移植潜力，并且在原发性和继发性受体中，表达AML1a的细胞比例随着时间的推移而增加。此外，通过长期培养、鹅卵石形成和菌落测定，AML1a的表达显著增加了移植动物的原始和承诺祖细胞活性。相反，全长同种异构体AML1b的表达消除了移植潜能。在体外，AML1b促进分化，而AML1a促进能够短期植入淋巴细胞的祖细胞增殖。与这些发现一致，AML1a的相对丰度在人类脐带血的原始干细胞/祖细胞室中最高，并且在这些细胞中强制表达AML1a增强了体外和体内原始电位的维持。这些数据表明AML1的“a”亚型具有增强干细胞和祖细胞植入的能力，这两者都是成功的临床移植所必需的。这种活性与其在正常细胞和白血病细胞中的表达模式一致。操纵AML1亚型表达的平衡可能提供新的治疗策略，可用于白血病和成人脐带血移植，成人脐带血移植的干细胞和祖细胞数量通常有限。截断的AML1“a”亚型被证明具有增强干细胞和祖细胞植入的能力，这两者都是成功的临床移植所必需的。血液中含有红细胞（在全身携带氧气）、血小板（帮助血液凝结）和白细胞（抵抗感染）。所有这些定期被替换的细胞都来自于造血干细胞，即存在于骨髓中的造血细胞。像所有的干细胞一样，造血干细胞自我更新（自我繁殖）并产生承诺的祖细胞，这些祖细胞在造血过程中发育成成熟的血细胞。许多蛋白质控制造血，其中一些被称为转录因子；这些因子通过它们的DNA结合域与DNA结合，然后通过蛋白质的特定部分（它们的转录调节域）控制基因的表达（即DNA如何转化为蛋白质）。aml1蛋白是一种重要的造血转录因子，因其与急性髓性白血病（AML，一种血癌）有关而首次被发现。AML1基因的突变（改变）现在已知存在于其他类型的白血病中，这些白血病通常以未成熟血细胞过度增殖为特征。由于AML1在造血中起着至关重要的作用，更多地了解它调节哪些基因以及它的活性是如何被调节的，可能为治疗白血病和改善造血细胞移植提供线索。许多癌症治疗会破坏造血干细胞，使患者容易受到感染。骨髓或脐带血移植（怀孕期间连接母亲和婴儿的脐带血含有外周血干细胞）可以替代缺失的细胞，但脐带血中通常含有的干细胞不足，无法成功移植。因此，在移植前扩大这些组织的干细胞含量将是有用的。在这项研究中，研究人员在实验室（体外）和动物（体内）研究了AML1对造血干细胞和祖细胞自我更新和分化的影响。特别是，他们已经询问了AML1的两种亚型（密切相关的版本）如何影响这些细胞在移植后在小鼠体内生长和分化（移植）的能力。研究人员在小鼠造血干细胞和祖细胞中人工表达AML1a和AML1b（两种亚型都含有DNA结合结构域，但只有AML1b具有转录调节结构域），然后测试了这些细胞在小鼠体内的移植能力。表达aml1a的细胞比未改变的细胞移植得更好，并且在作为混合物移植时比未改变的细胞生长得更好。然而，表达aml1b的细胞不能移植。在体外，表达aml1a的细胞比表达aml1b的细胞生长得更快，表达aml1b的细胞分化更明显。为了研究这些亚型是否在人类细胞中具有相同的作用，研究人员测量了人类脐带血中祖细胞产生的AML1a和AML1b mRNA（蛋白质生产的模板）的数量。尽管AML1b（以及AML1c，一种具有相似特征的异构体）mRNA在所有祖细胞类型中占主导地位，但AML1a在干细胞和祖细胞中的相对丰度最大。此外，在这些细胞中强制表达AML1a提高了它们在体外分裂和在小鼠体内移植的能力。这些发现表明，AML1a的表达增加了造血干细胞和祖细胞的自我更新能力，从而提高了它们在小鼠体内的移植能力，而AML1b的表达促进了这些细胞类型的分化。这些活性与这两种亚型在正常造血细胞和白血病细胞中的表达模式一致——许多白血病细胞产生的突变AML类似于AML1a。由于在这些实验中，AML1亚型的表达水平高于正常水平，因此这些发现的生理学相关性需要通过证明正常水平的AML1a和AML1b产生相似的结果来证实。然而，这些结果表明，操纵造血细胞产生的AML1亚型的平衡可能在临床上有用。在白血病中，向AML1b表达的转变可能会减缓白血病细胞的增殖并促进它们的分化。相反，在脐带血移植中，向AML1a表达的转变可能通过扩大干细胞和祖细胞群来改善患者的预后。请通过本摘要的在线版本http://dx.doi.org/10.1371/journal.pmed.0040172访问这些网站。维基百科有关于造血和造血干细胞的页面(注：维基百科是一个免费的在线百科全书，任何人都可以编辑；美国国家癌症研究所有一份关于骨髓和外周血干细胞移植的情况说明书（英语和西班牙语），以及白血病患者和专业人员的信息（英语）。美国血液学会提供关于血液疾病的患者信息，包括骨髓和干细胞移植的信息
AML1/RUNX1 is the most frequently mutated gene in leukaemia and is central to the normal biology of hematopoietic stem and progenitor cells. However, the role of different AML1 isoforms within these primitive compartments is unclear. Here we investigate whether altering relative expression of AML1 isoforms impacts the balance between cell self-renewal and differentiation in vitro and in vivo. The human AML1a isoform encodes a truncated molecule with DNA-binding but no transactivation capacity. We used a retrovirus-based approach to transduce AML1a into primitive haematopoietic cells isolated from the mouse. We observed that enforced AML1a expression increased the competitive engraftment potential of murine long-term reconstituting stem cells with the proportion of AML1a-expressing cells increasing over time in both primary and secondary recipients. Furthermore, AML1a expression dramatically increased primitive and committed progenitor activity in engrafted animals as assessed by long-term culture, cobblestone formation, and colony assays. In contrast, expression of the full-length isoform AML1b abrogated engraftment potential. In vitro, AML1b promoted differentiation while AML1a promoted proliferation of progenitors capable of short-term lymphomyeloid engraftment. Consistent with these findings, the relative abundance of AML1a was highest in the primitive stem/progenitor compartment of human cord blood, and forced expression of AML1a in these cells enhanced maintenance of primitive potential both in vitro and in vivo. These data demonstrate that the “a” isoform of AML1 has the capacity to potentiate stem and progenitor cell engraftment, both of which are required for successful clinical transplantation. This activity is consistent with its expression pattern in both normal and leukaemic cells. Manipulating the balance of AML1 isoform expression may offer novel therapeutic strategies, exploitable in the contexts of leukaemia and also in cord blood transplantation in adults, in whom stem and progenitor cell numbers are often limiting. The truncated "a" isoform of AML1 is shown to have the capacity to potentiate stem and progenitor cell engraftment, both of which are required for successful clinical transplantation. Blood contains red blood cells (which carry oxygen round the body), platelets (which help the blood to clot), and white blood cells (which fight off infections). All these cells, which are regularly replaced, are derived from hematopoietic stem cells, blood-forming cells present in the bone marrow. Like all stem cells, hematopoietic stem cells self-renew (reproduce themselves) and produce committed progenitor cells, which develop into mature blood cells in a process called hematopoiesis. Many proteins control hematopoiesis, some of which are called transcription factors; these factors bind to DNA through their DNA-binding domain and then control the expression of genes (that is, how DNA is turned into proteins) through particular parts of the protein (their transcription regulatory domains). An important hematopoietic transcription factor is AML1—a protein first identified because of its involvement in acute myelogenous leukemia (AML, a form of blood cancer). Mutations (changes) in the AML1 gene are now known to be present in other types of leukemia, which are often characterized by overproliferation of immature blood cells. Because of AML1′s crucial role in hematopoiesis, knowing more about which genes it regulates and how its activity is regulated could provide clues to treating leukemia and to improving hematopoietic cell transplantation. Many cancer treatments destroy hematopoietic stem cells, leaving patients vulnerable to infection. Transplants of bone marrow or cord blood (the cord that links mother and baby during pregnancy contains peripheral blood stem cells) can replace the missing cells, but cord blood in particular often contains insufficient stem cells for successful transplantation. It would be useful, therefore, to expand the stem cell content of these tissues before transplantation. In this study, the researchers investigated the effect of AML1 on self-renewal and differentiation of hematopoietic stem and progenitor cells in the laboratory (in vitro) and in animals (in vivo). In particular, they have asked how two isoforms (closely related versions) of AML1 affect the ability of these cells to grow and differentiate (engraft) in mice after transplantation. The researchers artificially expressed AML1a and AML1b (both isoforms contain a DNA binding domain, but only AML1b has transcription regulatory domains) in mouse hematopoietic stem and progenitor cells and then tested the cells' ability to engraft in mice. AML1a-expressing cells engrafted better than unaltered cells and outgrew unaltered cells when transplanted as a mixture. AML1b-expressing cells, however, did not engraft. In vitro, AML1a-expressing cells grew more than AML1b-expressing cells, whereas differentiation was promoted in AML1b-expressing cells. To investigate whether the isoforms have the same effects in human cells, the researchers measured the amount of AML1a and AML1b mRNA (the template for protein production) made by progenitor cells in human cord blood. Although AML1b (together with AML1c, an isoform with similar characteristics) mRNA predominated in all the progenitor cell types, the relative abundance of AML1a was greatest in the stem and progenitor cells. Furthermore, forced expression of AML1a in these cells improved their ability to divide in vitro and to engraft in mice. These findings indicate that AML1a expression increases the self-renewal capacity of hematopoietic stem and progenitor cells and consequently improves their ability to engraft in mice, whereas AML1b expression encourages the differentiation of these cell types. These activities are consistent with the expression patterns of the two isoforms in normal hematopoietic cells and in leukemic cells—the mutated AML made by many leukemic cells resembles AML1a. Because the AML1 isoforms were expressed at higher than normal levels in these experiments, the physiological relevance of these findings needs to be confirmed by showing that normal levels of AML1a and AML1b produce similar results. Nevertheless, these results suggest that manipulating the balance of AML1 isoforms made by hematopoietic cells might be useful clinically. In leukemia, a shift toward AML1b expression might slow the proliferation of leukemic cells and encourage their differentiation. Conversely, in cord blood transplantation, a shift toward AML1a expression might improve patient outcomes by expanding the stem and progenitor cell populations. Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0040172. Wikipedia has pages on hematopoiesis and hematopoietic stem cells (note: Wikipedia is a free online encyclopedia that anyone can edit; available in several languages) The US National Cancer Institute has a fact sheet on bone marrow and peripheral blood stem cell transplantation (in English and Spanish) and information for patients and professionals on leukemia (in English) The American Society of Hematology provides patient information about blood diseases, including information on bone marrow and stem cell transplantation
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影响因子：
8
作者：
Cantor, AB;Orkin, SH
通讯作者：
Orkin, SH
影响因子：
20.3
作者：
Christiansen, DH;Andersen, MK;Pedersen-Bjergaard, J
通讯作者：
Pedersen-Bjergaard, J
影响因子：
82.9
作者：
Ichikawa, M;Asai, T;Kurokawa, M
通讯作者：
Kurokawa, M
影响因子：
5.2
作者：
de Wynter, EA;Buck, D;Testa, NG
通讯作者：
Testa, NG
DOI：
10.1084/jem.20031556
发表时间：
2004-10-04
期刊：
The Journal of experimental medicine
影响因子：
--
作者：
Ling KW;Ottersbach K;van Hamburg JP;Oziemlak A;Tsai FY;Orkin SH;Ploemacher R;Hendriks RW;Dzierzak E
通讯作者：
Dzierzak E