Bcl11b in early T cell development

描述（由申请人提供）：已知T细胞谱系定型依赖于在Notch-Delta信号传导影响下操作的转录因子的组合。然而，这些因素在谱系定型的分子机制中的确切作用仍然是难以捉摸的。一个问题是，所有已建立的因子本身都在干细胞维持和/或其他造血细胞类型以及T细胞中发挥作用，即使用于T细胞特化的精确组合可能是独特的。另一个问题是在血统承诺期间被排除在外的选择的复杂性。T细胞前体似乎保留了进入自然杀伤（NK）细胞发育和树突细胞发育的非常不同的途径，也可能进入肥大细胞和巨噬细胞发育的途径，直到其规格的中点，然后似乎立即失去所有这些替代潜力。与此同时，这些细胞似乎改变了它们的自我更新潜力。很难在一步过程中解释所有这些变化，特别是在缺乏任何已知的明显是T细胞特异性的调节功能的情况下。一直缺少的是T细胞系特异性调节因子，可以显示出控制这些事件的精确定义的子集。 这是我们提出的Bcl 11b所起的作用，Bcl 11b是一种最近表征的转录因子，在造血系统中具有高度T系特异性的表达模式。Bcl 11b诱导T细胞系的承诺，我们的初步数据与条件Bcl 11b敲除意味着，这个因素控制一个离散的子集的谱系承诺功能，涉及抑制NK细胞的命运和干细胞或祖细胞特异性的维护途径。在这个应用程序中，我们建议测试这个模型，并使用Bcl 11b澄清在承诺过程中的监管联系。目标是：1.使用Bcl 11 B缺陷来剖析T谱系定型机制中的组成过程：（a）排除NK和干细胞调节程序，因为这与排除骨髓、B和其他造血程序有关;和（B）定型机制可能区分12个谱系T细胞和34个谱系T细胞2。确定Bcl 11b和Id/E蛋白比例在早期T细胞发育中的调节联系3.确定Bcl 11b的直接靶点和Bcl 11b作用促进T细胞系身份的有序途径4.使用新的荧光敲入报告基因整合到Bcl 11b基因座中，在单细胞水平上跟踪T细胞系的特化和定型。

DESCRIPTION (provided by applicant): T cell lineage commitment is known to depend on a combination of transcription factors operating under the influence of Notch-Delta signaling. However, the exact roles of these factors in the molecular mechanism of lineage commitment have remained elusive. One problem is that all of the established factors themselves have roles in stem-cell maintenance and/or in other hematopoietic cell types as well as in T cells, even though the precise combination used for T-cell specification may be unique. Another problem is the complexity of the choices that are excluded during lineage commitment. T-cell precursors appear to retain access to the very distinct pathways of natural killer (NK) cell development and dendritic- cell development, possibly also to mast-cell and macrophage development, until a midpoint in their specification, and then appear to lose all these alternative potentials at once. At the same time, the cells appear to alter their self-renewal potential. It has been difficult to account for all these changes in a one- step process, especially in the absence of any known regulatory function that is clearly T-cell specific. What has been missing is a T-lineage specific regulatory factor that can be shown to control a precisely defined subset of these events. This is the role that we propose is played by Bcl11b, a recently characterized transcription factor with a highly T-lineage specific pattern of expression within the hematopoietic system. Bcl11b induction immediately precedes T-lineage commitment, and our preliminary data with a conditional Bcl11b knockout imply that this factor controls a discrete subset of lineage commitment functions, involving the repression of NK fates and stem or progenitor cell-specific maintenance pathways. In this application, we propose to test this model and to use Bcl11b to clarify regulatory linkages in the commitment process. The aims are: 1. To use Bcl11b deficiency to dissect component processes within the T-lineage commitment mechanism: (a) exclusion of NK and stem-cell regulatory programs as related to exclusion of myeloid, B, and other hematopoietic programs; and (b) commitment mechanisms that may distinguish 12 from 34 lineage T cells 2. To determine the regulatory links between Bcl11b and the Id/E protein ratio in early T-cell development 3. To determine the direct targets of Bcl11b and the ordered pathway through which Bcl11b action promotes T-lineage identity 4. To track T-lineage specification and commitment at the single cell level using new fluorescent knock- in reporters incorporated in the Bcl11b locus.