Analysis of a murine model of the AML1-ETO translocation

描述（由申请人提供）：t（8;21）（q22;q22）易位融合了人8号染色体上的ETO基因和21号染色体上的AML 1基因，是与急性髓性白血病（AML）相关的最常见的细胞遗传学异常之一。它见于大约12- 15%的AML病例，并且存在于大约40%的M2表型AML中。我们通过逆转录病毒转导纯化的造血干细胞（HSC）产生了t（8;21）的小鼠模型。用表达AML 1- ETO的HSC重建的小鼠在干细胞区室和髓系内显示出明显的发育异常。移植后10个月，原始成髓细胞增加到骨髓的约10%。与该观察结果一致的是体外髓系集落形成细胞增加50倍。表现出异常嗜碱性肉芽的嗜酸性粒细胞也增加。10个月大的重组动物骨髓中的HSC数量是移植匹配对照小鼠的29倍，表明AML 1-ETO表达超过了HSC池大小的正常遗传控制。总之，表达AML 1-ETO的动物重现了t（8;21）人类患者中观察到的许多（也许是所有）发育异常，尽管这些动物不会发生白血病或外周组织（如肝脏或脾脏）中的播散性疾病。这表明继发性突变是发展为急性白血病所必需的。本提案的主要目标是了解AML 1-ETO在HSC中表达引起的发育功能障碍的潜在分子和细胞基础。具体目标将集中在（1），表达AML 1-ETO的成髓细胞的表型和功能表征（2），确定AML 1-ETO对HSC自我更新的影响并鉴定候选自我更新基因（3），表征与AML 1-ETO协同诱导AML的继发突变和（4），ETO内负责HSC和成髓细胞中观察到的发育表型的结构域的功能定位。

DESCRIPTION (provided by applicant): The t(8;21)(q22;q22) translocation, which fuses the ETO gene on human chromosome 8 with the AML1 gene on chromosome 21, is one of the most frequent cytogenetic abnormalities associated with acute myeloid leukemia (AML). It is seen in approximately 12-15 percent of AML cases and is present in about 40 percent of AML with an M2 phenotype. We have generated a murine model of the t(8;21) by retroviral transduction of purified hematopoietic stem cells (HSC). Mice reconstituted with HSC that express AML 1- ETO show distinct developmental abnormalities in the stem cell compartment and within the myeloid lineages. Primitive myeloblasts were increased to approximately 10 percent of bone marrow by ten months post-transplant. Consistent with this observation was a 50-fold increase in myeloid colony forming cells in vitro. Eosinophil myelocytes that exhibited abnormal basophilic granulation were also increased. HSC numbers in the bone marrow of 10-month-old reconstituted animals were 29-fold greater than in transplant-matched control mice, suggesting that AML1-ETO expression overrides the normal genetic control of HSC pool size. In summary, AML1-ETO-expressing animals recapitulate many (and perhaps all) of the developmental abnormalities seen in human patients with the t(8;21), although the animals do not develop leukemia or disseminated disease in peripheral tissues like the liver or spleen. This suggests that secondary mutations are required to progress to acute leukemia. The primary goal of this proposal is to understand the underlying molecular and cellular basis for the developmental dysfunction caused by AML1-ETO expression in HSC. The specific aims will focus on (1), phenotypic and functional characterization of AML1-ETO expressing myeloblasts (2), determining the influence of AML1-ETO on HSC self renewal and identification of candidate self-renewal genes (3), characterization of secondary mutations that cooperate with AML1-ETO to induce AML and (4), functional mapping of domains within ETO that are responsible for the developmental phenotypes observed in HSC and myeloblasts.