David-Fung Elizabeth-Sharon, Butler Robert, Buzi Gentian, Yui Mary A, Diamond Rochelle A, Anderson Michele K, Rowen Lee, Rothenberg Ellen V
Division of Biology 156-29, California Institute of Technology, Pasadena, CA 91125, USA.
Dev Biol. 2009 Jan 15;325(2):444-67. doi: 10.1016/j.ydbio.2008.10.021. Epub 2008 Nov 5.
Mammalian T lymphocytes are a prototype for development from adult pluripotent stem cells. While T-cell specification is driven by Notch signaling, T-lineage commitment is only finalized after prolonged Notch activation. However, no T-lineage specific regulatory factor has been reported that mediates commitment. We used a gene-discovery approach to identify additional candidate T-lineage transcription factors and characterized expression of >100 regulatory genes in early T-cell precursors using realtime RT-PCR. These regulatory genes were also monitored in multilineage precursors as they entered T-cell or non-T-cell pathways in vitro; in non-T cells ex vivo; and in later T-cell developmental stages after lineage commitment. At least three major expression patterns were observed. Transcription factors in the largest group are expressed at relatively stable levels throughout T-lineage specification as a legacy from prethymic precursors, with some continuing while others are downregulated after commitment. Another group is highly expressed in the earliest stages only, and is downregulated before or during commitment. Genes in a third group undergo upregulation at one of three distinct transitions, suggesting a positive regulatory cascade. However, the transcription factors induced during commitment are not T-lineage specific. Different members of the same transcription factor family can follow opposite trajectories during specification and commitment, while factors co-expressed early can be expressed in divergent patterns in later T-cell development. Some factors reveal new regulatory distinctions between alphabeta and gammadelta T-lineage differentiation. These results show that T-cell identity has an essentially complex regulatory basis and provide a detailed framework for regulatory network modeling of T-cell specification.
哺乳动物T淋巴细胞是成年多能干细胞发育的一个典型例子。虽然T细胞的特化由Notch信号驱动，但T细胞谱系的确定只有在Notch信号长期激活后才最终完成。然而，尚未报道有介导谱系确定的T细胞谱系特异性调节因子。我们采用基因发现方法来鉴定额外的候选T细胞谱系转录因子，并使用实时RT-PCR对早期T细胞前体中100多个调节基因的表达进行了表征。这些调节基因在多谱系前体体外进入T细胞或非T细胞途径时、在体外非T细胞中以及在谱系确定后的T细胞后期发育阶段也受到监测。观察到至少三种主要的表达模式。最大一组中的转录因子在整个T细胞谱系特化过程中以相对稳定的水平表达，这是胸腺前体的遗留特征，其中一些在谱系确定后持续表达，而另一些则下调。另一组仅在最早阶段高度表达，并在谱系确定前或确定过程中下调。第三组中的基因在三个不同的转变之一发生上调，表明存在一个正向调节级联。然而，在谱系确定过程中诱导的转录因子并非T细胞谱系特异性的。同一转录因子家族的不同成员在特化和谱系确定过程中可能遵循相反的轨迹，而早期共表达的因子在后期T细胞发育中可能以不同的模式表达。一些因子揭示了αβ和γδ T细胞谱系分化之间新的调节差异。这些结果表明，T细胞身份具有本质上复杂的调节基础，并为T细胞特化的调节网络建模提供了详细框架。
