Molecular Triggers of T Helper Lineage Choice

胸腺细胞分化为交替的T杀伤细胞和辅助T细胞是非常有意义的，因为它在塑造T细胞隔间和作为二元谱系决定的范例中具有重要意义。一个日益增长的共识是，谱系选择是由T细胞受体(TCR)信号的差异决定的，尽管分子基础仍然知之甚少。最近，转录因子Zbtb7b被确定为谱系选择的“主调节因子”，它的表达是触发T辅助命运的必要条件和充分条件。在这个应用中，我们打算通过解决以下问题来阐明TCR信号控制谱系选择的机制：1.Zbtb7b转录在DP阶段的抑制是如何控制的？DP胸腺细胞不表达Zbtb7b，即使在抗体介导的TCR交联剂作用下也是如此。我们将确定DP胸腺细胞中Zbtb7b基因座的沉默是由表观遗传还是由抑制性转录因子决定的，以及正在经历T杀手谱系的胸腺细胞。2.Ptprk在CD4谱系承诺中的作用是什么？在缺乏受体Tyr磷酸酶Ptprk的大鼠中，T辅助细胞系的发育被特异性地阻止，这表明在介导II类限制性TCR信号方面起着重要作用。我们将产生Ptprk-/-小鼠来测试Ptprk是否在小鼠中介导类似的功能，如果是的话，它是否直接影响CD4谱系承诺。这些实验应该提供对交替TCR信号的分子基础和谱系承诺的机制的见解。

Differentiation of thymocytes into alternate T killer and helper lineages is of great interest, due to its importance in shaping the T cell compartment and as a paradigm of binary lineage decisions. A growing consensus exists that lineage choice is determined instructively by differences in T cell receptor (TCR) signalling, although the molecular basis remains poorly understood. Recently, the transcription factor Zbtb7b has been identified as a "master regulator" of lineage choice, whose expression is necessary and sufficient to trigger the T helper fate. In this application, we propose to elucidate the mechanism by which TCR signaling controls lineage choice, by addressing the following questions: 1. How is repression of Zbtb7b transcription at the DP stage controlled? DP thymocytes do not express Zbtb7b, even when subjected to antibody-mediated TCR crosslinking. We will determine whether silencing of the Zbtb7b locus in DP thymocytes, as well as thymocytes undergoing commitment to the T killer lineage, is determined epigenetically or by repressive transcription factors. 2. What is the role of Ptprk in CD4 lineage commitment? T helper lineage development is specifically blocked in rats lacking the receptor Tyr phosphatase Ptprk, suggesting an essential role in mediating class II-restricted TCR signals. We will generate Ptprk-/- mice to test if Ptprk mediates a similar function in mice, and if so whether it affects CD4 lineage commitment directly. These experiments should provide insights into the molecular basis of alternate TCR signaling and the mechanism of lineage commitment.