Peterson Luke F, Lo Miao-Chia, Okumura Akiko Joo, Zhang Dong-Er
Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
Blood Cells Mol Dis. 2007 Nov-Dec;39(3):321-8. doi: 10.1016/j.bcmd.2007.06.012. Epub 2007 Aug 9.
The t(8;21)(q22:q22) translocation associated with acute myeloid leukemia fuses the AML1/RUNX1 N-terminal portion located on chromosome 21 to most of the ETO/MTG8 gene on chromosome 8. Various investigators have shown that the fusion product AML1-ETO on its own is unable to promote leukemia. Early studies using transgenic mouse models demonstrated that the direct knock-in of the fusion protein expression is embryonic lethal, similar to the AML1 knockout, suggesting that AML1-ETO has a dominant negative role over AML1. Using the embryonic stem cells generated for such studies, we show here that the presence of the fusion product AML1-ETO blocks definitive hematopoiesis in vitro as well, in both one and two step methylcellulose methods of embryonic stem cell hematopoietic differentiation. However, there is a very low occurrence of macrophage colonies, similar to the knock-in mice that display macrophages in cell cultures of yolk sac derived cells. In addition, we show that exogenous expression of AML1 is unable to bypass this AML1-ETO induced definitive hematopoietic block in these cells. This inability is not linked to an inability to reverse gene expression inhibition by AML1-ETO of the PU.1 gene associated with stem cell maintenance and myeloid differentiation. Our results suggest that AML1-ETO functions in a complex competitive manner with AML1 involving transcriptional regulation, protein-protein interactions and post-transcriptional mechanism(s) affecting early embryonic hematopoiesis and possibly leukemogenesis.
与急性髓系白血病相关的t(8;21)(q22:q22)易位将位于21号染色体上的AML1/RUNX1 N端部分与8号染色体上的大部分ETO/MTG8基因融合。多位研究者已表明，融合产物AML1-ETO自身无法促进白血病发生。早期使用转基因小鼠模型的研究表明，融合蛋白表达的直接敲入具有胚胎致死性，类似于AML1基因敲除，这表明AML1-ETO对AML1具有显性负性作用。利用为此类研究生成的胚胎干细胞，我们在此表明，在胚胎干细胞造血分化的一步和两步甲基纤维素方法中，融合产物AML1-ETO的存在也会在体外阻断确定性造血。然而，巨噬细胞集落的发生率非常低，类似于在卵黄囊来源细胞的细胞培养中显示巨噬细胞的敲入小鼠。此外，我们表明，AML1的外源性表达无法绕过这些细胞中由AML1-ETO诱导的确定性造血阻滞。这种无能与无法逆转AML1-ETO对与干细胞维持和髓系分化相关的PU.1基因的基因表达抑制无关。我们的结果表明，AML1-ETO与AML1以复杂的竞争方式发挥作用，涉及转录调控、蛋白质-蛋白质相互作用以及影响早期胚胎造血和可能的白血病发生的转录后机制。
