Mechanisms of Leukemogenic Transformation by MLL-CALM

描述（由申请人提供）：涉及染色体11q23的混合谱系白血病（MLL）基因的染色体重排在白血病中很常见。尽管已经确定了40多个MLL易位伴侣基因，但MLL融合伴侣蛋白导致白血病的确切机制仍不清楚。我们最近在一名患有急性髓性白血病（AML）的婴儿中发现了一个新的11号染色体倒置，将MLL与网格蛋白组装淋巴髓性白血病（CALM）基因11q14并置。在急性白血病和淋巴瘤中，CALM首先被确定为AF10的易位伴侣（AF10本身是MLL伴侣）。CALM蛋白直接与网格蛋白和膜脂相互作用，在胞吞作用和细胞内囊泡运输中起关键作用。最近，小鼠平静基因的突变已被证明可以解释填充小鼠的表型，填充小鼠在造血和铁代谢方面具有显着异常。在造血恶性肿瘤中，CALM作为两种不同基因的易位伙伴参与，同时它也参与正常的造血，这表明正常的CALM功能的扰动有助于白血病的发展。本研究的总体目的是研究MLL-CALM融合蛋白在白血病发生中的生物学作用。我们假设MLL-CALM易位通过扰乱CALM和MLL的正常功能来促进髓系白血病的发展。为了开始了解MLL-CALM蛋白参与AML发病的机制，我们的第一个目标是确定MLL-CALM的表达是否导致体外转化和体内白血病。我们将利用小鼠造血祖细胞转化实验严格证明MLL-CALM的表达在体外导致转化，并建立MLL-CALM依赖性白血病的小鼠体内模型。此外，为了更真实地模拟MLL-CALM白血病表型，我们将制备MLL-CALM转基因小鼠。最后，我们将在fit1衍生的造血前体的背景下研究白血病的发生。我们的第二个总体目标是确定与mll - calm相关的转换所涉及的机制。在这些研究中，我们将重点关注三种特定机制-二聚化，转录调节和内吞作用-在MLL-CALM-和calm - af10依赖性转化中的作用。关于CALM功能的见解可以推广到大量具有CALM- af10易位的白血病和淋巴瘤，并且在更广泛的意义上，将有助于我们对正常的CALM生物学的理解。

DESCRIPTION (provided by applicant): Chromosomal rearrangements involving the Mixed Lineage Leukemia (MLL) gene at chromosome 11q23 are frequently seen in leukemias. Although more than 40 translocation partner genes have been identified for MLL, the precise mechanisms by which MLL-fusion partner proteins lead to leukemia remain unclear. We recently identified a novel chromosome 11 inversion in an infant with acute myeloid leukemia (AML) that juxtaposed MLL to the Clathrin Assembly Lymphoid Myeloid Leukemia (CALM) gene at 11q14. CALM was first identified as a translocation partner for AF10 - itself an MLL partner - in acute leukemias and lymphomas. The CALM protein directly interacts with clathrin and membrane lipids, and plays a key role in endocytosis and intracellular vesicle trafficking. Recently, mutations in the murine calm gene have been shown to account for the phenotype of the fill mouse, which has significant abnormalities in hematopoiesis and iron metabolism. The involvement of CALM as a translocation partner for two distinct genes in hematopoietic malignancies, together with its involvement in normal hematopoiesis, suggests that perturbation of normal CALM function contributes to the development of leukemia. The overall objective of this proposal is to study the biology of the MLL-CALM fusion protein in leukemogenesis. We hypothesize that the MLL-CALM translocation contributes to the development of myeloid leukemia by perturbing the normal function of both CALM and MLL. To begin to understand mechanisms by which the MLL-CALM protein is involved in the pathogenesis of AML, our first aim is to determine whether MLL-CALM expression results in transformation in vitro and leukemia in vivo. We will use the murine hematopoietic progenitor transformation assay to rigorously demonstrate that MLL-CALM expression results in transformation in vitro, and establish in vivo murine models of MLL-CALM-dependent leukemia. In addition, to more faithfully mimic the MLL-CALM leukemia phenotype, we will prepare an mll-CALM transgenic mouse. Finally, we will examine leukemogenesis in the context of fit1 -derived hematopoietic precursors. Our second overall aim is to identify mechanisms involved in MLL-CALM-dependent transformation. In these studies, we will focus on the role of three specific mechanisms - dimerization, transcriptional regulation and endocytosis - in MLL-CALM- and CALM-AF10-dependent transformation. Insights gained regarding CALM function may be generalizable to the large number of leukemias and lymphomas with CALM-AF10 translocations, and, in a broader sense, will contribute to our understanding of normal CALM biology.