Signaling in the DN to DP thymocyte transition

描述（由申请人提供）：在胸腺细胞发育的CD44- CD25+ (DN3)阶段，tcr - β基因的有效重排和与不变的前tcr - α和CD3亚基的组装导致细胞表面形成前tcr复合物。细胞自主和不依赖配体的tcr前信号转导触发一系列复杂的信号转导事件，导致未成熟胸腺细胞的存活、增殖和分化。在tcr前活性开始后的阶段中发挥重要作用的级联反应之一是wnt/ β -连环蛋白途径。β -连环蛋白是wnt信号的中心介质，该通路激活后，β -连环蛋白的稳定性导致其转运到细胞核，在细胞核中结合并激活TCF/LEF转录因子。TCF-1和LEF-1（淋巴细胞特异性β -连环蛋白调节的转录因子）的缺乏会导致胎儿胸腺器官培养（FTOC）中未成熟单阳性阶段的胎儿胸腺细胞发育完全受阻。β -catenin与TCF-1的相互作用是该蛋白在DN到DP转变过程中的作用所必需的，并且β -catenin的体细胞稳定可以在缺乏pre-TCR和ab-TCR信号的情况下介导发育进程。wnt/ β -catenin通路参与这一发育阶段的确切功能机制、分子成分和特异性靶点仍有待阐明。鉴于这种发育转变依赖于tcr前信号传导，因此专门研究tcr前和wnt/ β -连环蛋白信号级联之间的相互作用变得很重要。本研究的重点是剖析从DN到DP胸腺细胞转变过程中wnt/ β -catenin信号转导的要求，以及确定tcr前和wnt/ β -catenin信号转导级联之间的相互作用。

DESCRIPTION (provided by applicant): Productive rearrangement of TCR-beta genes at the CD44- CD25+ (DN3) stage of thymocyte development and assembly with the invariant pre-TCR-alpha and CD3 subunits leads to the formation of a pre-TCR complex on the cell surface. Cell autonomous and ligand independent pre-TCR signaling triggers a complex cascade of signaling events leading to the survival, proliferation and differentiation of immature thymocytes. One of the cascades that play an essential role in the stages following the onset of pre-TCR activity is the wnt/beta-catenin pathway. Beta-catenin is the central mediator of wnt signaling, whose stabilization in response to activation of this pathway results to its transport to the nucleus, where it binds to and activates the TCF/LEF transcription factors. Deficiency for both TCF-1, and LEF-1, lymphocyte specific beta-catenin regulated transcription factors, results in a complete block of fetal thymocyte development in fetal thymic organ cultures (FTOC) at the immature single positive stage. Interaction of beta-catenin with TCF-1 is necessary for the action of this protein during the DN to DP transition, and somatic stabilization of beta-catenin can mediate developmental progression in the absence of pre-TCR and ab-TCR signaling. The exact mechanism of function as well as the molecular components and specific targets of the wnt/beta-catenin pathway involved in this developmental stage remain to be elucidated. In view of the fact that this developmental transition depends on pre-TCR signaling it becomes important to specifically examine the interaction between the pre-TCR and the wnt/beta- catenin signaling cascades. The present proposal focuses at dissecting the requirement for wnt/beta-catenin signaling in the DN to DP thymocyte transition as well as determining the interaction between pre-TCR and wnt/beta-catenin signaling cascades.