Genetic mechanisms regulating B-lymphocyte commitment

描述（由申请方提供）：寡能共同淋巴祖细胞向B淋巴细胞定向转化的途径和分子机制仍不清楚。最近的研究表明，转录因子，早期B细胞因子（EBF）和Pax 5，可能在调节B细胞谱系的启动和维持中起重要作用。在不存在EBF或Pax 5的情况下发育的小鼠中，B细胞发育在谱系定型（EBF）之前被阻止或B定型状态的维持不能持续（Pax 5）。EBF可以直接结合并激活Pax 5启动子的发现表明，这两个因子可能在控制B细胞命运的共同调节级联中起作用。这一观点得到了该提议中描述的研究的支持，其中造血干细胞中EBF或Pax 5的强制表达足以确定体内B细胞与T细胞的身份。用表达EBF或Pax 5的细胞重建的所有动物在移植后至少10个月的外周血和脾脏中表现出大于90%的供体来源的B系细胞，胸腺中基本上没有T淋巴细胞生成。B细胞谱系发育的强烈倾斜不是由于恶性肿瘤，而是EBF或Pax 5表达的特异性。重叠的表型进一步表明，EBF和Pax 5可能在互补的途径中发挥作用，以控制B系决定的最早期事件。为了验证这一假设，我们建议（1）定位EBF和Pax 5中负责促进B细胞发育和抑制T-谱系定型的结构域，（2）鉴定在EBF-/-动物背景下激活B细胞发育的EBF下游靶基因，（3）确定EBF和/或Pax 5是否足以拯救PU缺陷遗传背景中的B细胞发育。1、Ikaros或E2 A的信号传导，以及（4）确定通过Notch 1途径的信号传导是否影响EBF和/或Pax 5的表达或活性。这些研究将为在分子水平上控制B细胞发育的最早阶段的调节级联提供见解。

DESCRIPTION (provided by applicant): The pathways and molecular mechanisms responsible for B lymphocyte commitment from oligopotent common lymphoid progenitor cells remain largely unknown. Recent studies have suggested that the transcription factors, early B cell factor (EBF) and Pax5, may play a significant role in regulating both the initiation and maintenance of the B cell lineage. In mice that develop in the absence of EBF or Pax5, B cell development is arrested prior to lineage commitment (EBF) or the maintenance of the B committed state cannot be sustained (Pax5). Findings that EBF can directly bind and activate the Pax5 promoter suggest that these two factors may act in a common regulatory cascade that controls B cell fate. This notion is supported by studies described in this proposal, where enforced expression of either EBF or Pax5 in hematopoietic stem cells is sufficient to determine B versus T cell identity in vivo. All animals reconstituted with cells expressing EBF or Pax5 exhibit greater than 90 percent donor-derived B-lineage cells in the peripheral blood and spleen for at least 10 months post-transplant, with essentially no T lymphopoiesis occurring in the thymus. The strong skew in development to the B cell lineage was not due to malignancy and was specific for expression of either EBF or Pax5. The overlapping phenotypes further suggest that EBF and Pax5 may function in complementary pathways to control the earliest events in B-lineage determination. To test this hypothesis, we propose to (1) map domains within EBF and Pax5 that are responsible for both promotion of B cell development and inhibition of T-lineage commitment, (2) identify downstream target genes of EBF that activate B cell development in the context of EBF-/- animals, (3) define whether EBF and/or Pax5 are sufficient to rescue B cell development in genetic backgrounds deficient in PU. 1, Ikaros, or E2A and (4) determine whether signaling through the Notch1 pathway influences the expression or activity of EBF and/or Pax5. These studies will provide insights into the regulatory cascades that control the earliest stages of B cell development at the molecular level.