CONDITIONAL MUTAGENESIS TO STUDY C MYB FUNCTION

描述(申请人摘要)：很明显，c-myb原癌基因 在造血过程中起着至关重要的作用。在每个造血系中，c-myb 在分化的不成熟阶段大量表达，并被转变为 在分化过程中关闭的时间相对较晚。然而， 关于c-myb在造血过程中所起的作用，人们几乎一无所知。 成熟度，这一作用是如何调节的，或者是什么信号通路 调节c-myb的表达。C-myb基因纯合缺失的小鼠死亡 在严重贫血的胚胎发育过程中的第15天。这一发现 图形显示了c-myb在造血过程中的重要性，但 排除了对分化后期c-myb活性的研究。这个 缺乏一种易于处理的遗传系统，使c-myb基因在 后期的造血成熟一直是主要的障碍 了解c-myb在造血中的作用。在T细胞发育过程中 在胸腺中，c-myb在cd4/cd8双阳性胸腺细胞中表达，但 在CD4和CD8单项阳性中基本上检测不到的表达水平 细胞。在外周，c-myb在静息T细胞中不表达，但在 在GI晚期/S早期细胞周期中，表达于增殖的T细胞。 为了开始了解c-myb在T细胞发育中所起的作用，我们 产生了携带c-myb等位基因的小鼠，该等位基因以loxP位点为靶点 Cre重组酶的缺失。通过将这些小鼠培育成可用小鼠 将Cre表达定向到T细胞早期的菌株 在胸腺发育或诱导方式中，我们将定义其作用 C-myb在T细胞发育和效应器激活中的作用 功能。此外，这些老鼠将对这一领域至关重要，并将允许 开始深入了解c-myb在造血过程中的作用 就像在其他系统中一样，c-myb的功能仍然知之甚少。目标 1)确定c-myb的表达处于什么阶段 对T细胞的发育和功能至关重要，2)决定后果 C-myb的不适当表达对T细胞的发育和功能以及3) 确定推动T细胞发育所需的c-myb功能结构域 胸腺。

DESCRIPTION (Applicant's Abstract): It is clear that the c-myb protooncogene plays a crucial role during hematopoiesis. In each hematopoietic lineage, c-myb is abundantly expressed at the immature stages of differentiation and is turned off at a relatively late time during the differentiation process. However, virtually nothing is known about what role c-myb plays during hematopoietic maturation, how that role is mediated or what the signaling pathways are that regulate c-myb expression. Mice that are homozygous null at the c-myb locus die at day fifteen during embryogenesis from a severe anemia. This finding graphically demonstrated the significance of c-myb during hematopoiesis but has precluded study of c-myb activity at the later stages of differentiation. The lack of a tractable genetic system that will allow mutation of c-myb during the later stages of hematopoietic maturation has been a major impediment to understanding the role of c-myb during hematopoiesis. During T-cell development in the thymus, c-myb is expressed in CD4+CD8+ double positive thymocytes but is expressed at essentially undetectable levels in CD4+ and CD8+ single positive cells. In the periphery, c-myb is not expressed in resting T-cells, but is expressed in proliferating T-cells in late Gi/early S-phase of the cell cycle. To begin to understand the role played by c-myb during T-cell development we have produced mice that carry a c-myb allele targeted with loxP sites for deletion by the Cre recombinase. By breeding these mice to available mouse strains that direct Cre expression either to the early stages of T-cell development in the thymus or in an inducible fashion, we will define the role played by c-myb during T-cell development and the activation of effector functions. In addition, these mice will be crucial to the field and will allow one to begin to gain insight into c-myb function during hematopoiesis as well as in other systems where c-myb function remains poorly understood. The goals of this proposal are: 1) to determine at what stage c-myb expression is essential for T-cell development and function, 2) to determine the consequences of inappropriate c-myb expression to T-cell development and function and 3) to identify c-myb functional domains required to drive T-cell development in the thymus.