Analysis of Bcl11b function during thymocyte Differentiation

已经显示，任何选择后DP胸腺细胞在表达ThPOK时分化成CD 4谱系，而它们在不存在ThPOK时变成CD 8谱系细胞。因此，了解ThPOK基因的辅助谱系特异性表达是如何调控的至关重要。我们在ThPOK基因中发现了一个ThPOK沉默子，该沉默子在MHC I类选择性细胞向细胞毒谱系分化过程中抑制ThPOK基因的表达，为了揭示ThPOK沉默子活性的调控，我们对功能性较短的沉默子序列进行了下拉亲和纯化。通过对上述方法获得的几个候选物进行分子和生物学筛选后，Bcl 11b转录因子似乎在激活ThPOK沉默子中起重要作用。对Bcl 11b条件性基因敲除小鼠的遗传分析表明，ThPOK在预选择胸腺细胞和MHC I类选择细胞中的去抑制作用，导致MHC I类选择细胞向CD 4 ^+辅助细胞系细胞的细胞命运转换。这些结果表明，Bcl 11 b是中央调节辅助/细胞毒性谱系决定淋巴细胞通过调节ThPOK沉默活性。

It has been shown that any post-selection DP thymocytes differentiate into CD4-lineage upon expression of ThPOK, whereas they become CD8-linage cells in the absence of ThPOK. Therefore it is crucial to understand how helper-lineage specific expression of ThPOK gene is regulated. We have identified a ThPOK silencer in the ThPOK gene that is essential to repress ThPOK gene during differentiation of MHC class I selected cells toward the cytotoxic-lineage.In order to reveal regulation of ThPOK silencer activity, we performed pull down affinity purification with the functional shorter silencer sequences. After molecular and biological screening of several candidates obtained by the above approach, Bcl11b transcription factor appeared to play an essential role in activating ThPOK silencer. Genetic analysis of Bcl11b conditional knock-out mice showed that de-repression of ThPOK in both pre-selection thymocyte and in MHC class I selected cells, resulting in cell fate conversion of MHC class I selected cells to CD4^+helper lineage cells. These results suggested that Bcl11b is central to regulate helper/cytotoxic lineage decision by lymphocytes via regulation of ThPOK silencer activity.