CONDITIONAL MUTAGENESIS TO STUDY C MYB FUNCTION

描述（申请人的摘要）：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 在分化的未成熟阶段大量表达并转化为 在分化过程中相对较晚的时间关闭。然而， 对于 c-myb 在造血过程中的作用几乎一无所知 成熟，该作用是如何介导的或信号通路是什么 调节 c-myb 表达。 c-myb 基因座纯合无效的小鼠死亡 在胚胎形成过程中的第十五天，患有严重贫血。这一发现 图形化地证明了 c-myb 在造血过程中的重要性，但 排除了分化后期 c-myb 活性的研究。的 缺乏易于处理的遗传系统，使 c-myb 在 造血成熟的后期阶段是造血的主要障碍 了解 c-myb 在造血过程中的作用。 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 CD4 和 CD8 单阳性表达水平基本上不可检测 细胞。在外周，c-myb 在静息 T 细胞中不表达，但在 在细胞周期晚期 Gi/早期 S 期的增殖 T 细胞中表达。 为了开始了解 c-myb 在 T 细胞发育过程中所扮演的角色，我们 已经培育出携带 c-myb 等位基因的小鼠，该等位基因以 loxP 位点为目标 由 Cre 重组酶删除。通过将这些小鼠繁殖成可用的小鼠 将 Cre 表达引导至 T 细胞早期阶段的菌株 在胸腺中或以诱导方式发育，我们将定义角色 c-myb 在 T 细胞发育和效应子激活过程中发挥作用 功能。此外，这些小鼠对于该领域至关重要，并将允许 也开始深入了解造血过程中的 c-myb 功能 与其他系统一样，c-myb 的功能仍然知之甚少。目标 该提案的内容是：1）确定c-myb表达处于什么阶段 对于 T 细胞发育和功能至关重要，2) 确定后果 不适当的 c-myb 表达对 T 细胞发育和功能的影响，以及 3) 识别驱动 T 细胞发育所需的 c-myb 功能域 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.