Control of Lineage Commitment in Developing Thymocytes

描述（由申请人提供）：该项目的总体目标是了解控制 α/β 胸腺细胞对 CD4 或 CD8 谱系的选择性承诺的机制，并确保辅助受体表达与 I 类或 II 类 MHC 的 TCR 限制之间的精确相关性。尽管现在人们普遍认为响应 I 类或 II 类配体参与的替代 TCR 信号传导负责启动替代谱系定型，但实现这一目标的细胞内途径仍然未知。我们之前描述了一种独特的自发突变小鼠，称为“辅助缺陷”或HD，其中辅助受体表达和MHC特异性之间的相关性被破坏，使得所有胸腺细胞，特别是II类限制性胸腺细胞，采用CD8谱系。我们现在初步将缺陷基因鉴定为 cKrox，它是 POK 蛋白亚家族的一个很大程度上未表征的成员，其被定义为包含 Kr ppel 样锌指和 BTB/POZ 结构域，后者与转录抑制有关。基于这一最新发现，当前提案的重点是定义 cKrox 在发育中胸腺细胞中的功能特征、调节和细胞分布。我们提出以下具体目标： 1) 明确证明 cKrox 对应于 HD 基因座。 2) 确定 cKrox 活性在 I 类和 II 类特异性胸腺细胞中的差异调节方式。 3) 从功能上剖析 cKrox 的锌指和 BTB/POZ 结构域在谱系定型中的作用。

DESCRIPTION (provided by applicant): The overall aim of this project is to understand the mechanisms that control alternative commitment of alpha/beta thymocytes to the CD4 or CD8 lineages and that ensure the precise correlation between coreceptor expression and TCR restriction to class I or II MHC. Although it is now widely accepted that alternate TCR signaling in response to engagement by class I or II ligands is responsible for initiating alternate lineage commitment, the intracellular pathways through which this is accomplished remain unknown. We have previously described a unique spontaneous mutant mouse, termed "helper deficient" or HD, in which the correlation between coreceptor expression and MHC specificity breaks down, such that all thymocytes, in particular class II-restricted ones, adopt the CD8 lineage. We have now tentatively identified the defective gene as cKrox, a largely uncharacterized member of the POK subfamily of proteins, which are defined as containing both a Kr
ppel-like zinc finger and a BTB/POZ domain, the latter implicated in transcriptional repression. Based on this very recent finding, the current proposal focuses on defining the functional characteristics, regulation and cellular distribution of cKrox in developing thymocytes. We propose the following specific aims: 1) To definitively demonstrate that cKrox corresponds to the HD locus. 2) To determine how cKrox activity is differentially regulated in class I- versus class II-specific thymocytes. 3) To functionally dissect the roles of the zinc finger and BTB/POZ domains of cKrox in lineage commitment.