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谱系的替代承诺的机制，并确保辅助受体表达与TCR限制对I类或II类MHC之间的精确相关性。尽管现在人们普遍认为，响应I类或II类配体接合的交替TCR信号负责启动交替谱系接合，但完成这一过程的细胞内途径尚不清楚。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，其中辅助受体表达与MHC特异性之间的相关性被打破，因此所有胸腺细胞，特别是ii类限制性胸腺细胞，都采用CD8谱系。我们现在初步确定了缺陷基因为cKrox，这是POK蛋白亚家族的一个基本未被表征的成员，它被定义为包含Kr
pel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，目前的建议侧重于定义发育胸腺细胞中cKrox的功能特征、调节和细胞分布。我们提出以下具体目标：

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.