CONDITIONAL MUTAGENESIS TO STUDY C MYB FUNCTION

说明（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谱系中，c-myb 在分化的不成熟阶段大量表达， 在分化过程中相对较晚的时间关闭。然而，在这方面， 几乎没有人知道c-myb在造血过程中起什么作用。 成熟，这种作用是如何介导的，或者信号通路是什么， 调节c-myb表达。在c-myb基因座上纯合无效的小鼠死亡 在胚胎发生的第15天，由于严重贫血。这一发现 图中显示了c-myb在造血过程中的重要性， 排除了在分化后期对c-myb活性的研究。的 缺乏一个易于处理的遗传系统，将允许c-myb突变期间， 造血成熟的后期阶段一直是 了解c-myb在造血过程中的作用。在T细胞发育过程中 在胸腺中，c-myb在CD 4 + CD 8+双阳性胸腺细胞中表达， 在CD 4+和CD 8+单阳性中以基本上不可检测的水平表达 细胞在外周血中，c-myb在静息T细胞中不表达，但在静息T细胞中表达。 在细胞周期的G1晚期/S早期的增殖T细胞中表达。 为了开始了解c-myb在T细胞发育过程中的作用， 已经产生了携带c-myb等位基因的小鼠，该等位基因靶向loxP位点， 通过Cre重组酶进行缺失。通过将这些老鼠繁殖成可用的老鼠 将Cre表达引导至T细胞分化的早期阶段的菌株 在胸腺中或以诱导的方式发育，我们将定义 c-myb在T细胞发育和效应子激活中的作用 功能协调发展的此外，这些老鼠将是至关重要的领域，将允许 人们开始了解c-myb在造血过程中的功能 如在c-myb功能仍然知之甚少的其它系统中一样。的目标 该建议的主要内容是：1）确定c-myb表达在什么阶段 对T细胞发育和功能至关重要，2）确定后果 c-myb表达不当对T细胞发育和功能的影响; 3） 确定在T细胞中驱动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.