Control of Lineage Commitment in Developing Thymocytes

描述(由申请人提供)：本项目的总体目标是了解控制α/β胸腺细胞对CD4或CD8谱系的替代承诺的机制，并确保共受体表达与TCR对I类或II类MHC的限制之间的精确关联。尽管现在人们普遍认为，响应I类或II类配体参与的交替TCR信号负责启动交替谱系承诺，但细胞内完成这一承诺的途径仍不清楚。我们之前已经描述了一种独特的自发突变小鼠，称为“辅助缺陷”或HD，其中协同受体表达和MHC特异性之间的相关性被打破，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。我们现在已经初步确定缺陷基因为cKrox，它是Pok亚家族蛋白质中一个基本上没有特征的成员，它被定义为包含两个Kr蛋白样锌指和BTB/POZ结构域，后者参与转录抑制。基于这一最新发现，目前的建议侧重于定义cKrox在胸腺细胞发育中的功能特征、调节和细胞分布。我们提出了以下具体目标： 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是如何差异调节的。 3)从功能上剖析cKrox的锌指结构域和BTB/POZ结构域在谱系承诺中的作用。

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.