Control of Hematopoiesis by AP-1 and Bcl6

造血干细胞的增殖和分化受转录因子调控。本研究利用转基因小鼠和基因敲除小鼠分析了AP-1和Bcl-6两个即刻早期基因家族的作用，c-Fos与Jun家族形成AP-1复合物，调控AP-1结合基因的表达。c-fos在用细胞因子刺激的原始造血干细胞中瞬时上调。为了研究c-fos在造血中的作用，我们使用了携带干扰素诱导型Mx启动子控制下的c-fos基因的转基因小鼠（Mx-c-fos）和c-fos缺陷小鼠。c-fos在造血干细胞中的长期表达通过使其保持在细胞周期的G 0/G1期而抑制因子依赖性集落形成和基质依赖性造血。这些结果表明，c-fos诱导的造血干细胞负调控细胞周期进程，使其处于休眠状态。 ...更多信息 B细胞淋巴瘤中染色体易位断裂点及其产物作为序列特异性转录抑制因子的功能。Bcl-6在生殖中心B细胞分化中起重要作用。为了分析Bcl 6在B细胞发育中的作用，我们利用一种高效的逆转录病毒转导系统转导小鼠造血干细胞。我们构建了一个双顺反子逆转录病毒表达的小鼠Bcl 6和增强型绿色荧光蛋白（EGFP）。在SCF和IL-6存在的情况下，用该病毒感染Lin-Sca-1^+ BM细胞（造血干细胞部分），分选EGFP^+细胞并注射到2.5戈伊照射的SCID小鼠中，或在有或没有IL-7的OP-9基质细胞上共培养。用对照病毒（MSCV-EGFP）感染的BM细胞在体内和体外均增殖并分化为B细胞和髓样细胞。用Bcl 6病毒感染的BM细胞（MSCV-EGFP-Bcl 6）分化为髓样细胞，但B细胞分化受损。骨髓细胞高表达EGFP，而B细胞低表达或缺乏EGFP，而缺乏Bcl 6的造血干细胞可分化为骨髓细胞和B细胞。这些结果表明，Bcl 6的表达可用于指定造血系统中不同的细胞命运。少

Proliferation and differentiation of hematopoietic stem cells are regulated by transcriptional factors. In this study, we have analyzed role of two immediated early gene families, AP-1 and Bcl6 using transgenic mice and knock out mice.c-Fos forms AP-1 complex with Jun family and regulates the expression of AP-1 binding genes. c-fos is transiently upregulated in primitive hematopoietic stem cells stimulated with cytokines. To investigate the role of c-fos in hematopoiesis, we used transgenic mice carrying the c-fos gene under the control of the interferon-inducible Mx-promoter (Mx-c-fos) and c-fos deficient mice. Prolonged expression of c-fos in hematopoietic stem cells inhibited factor dependent colony formation and stroma dependent hematopoiesis by keeping them at G0/G1 phase of the cell cycle. These result suggest that the c-fos induced i hematopoietic stem cells negatively control s cell cycle progression and maintains them in a dormant state.The Bcl6 gene has been identified from t … More he chromosomal translocation breakpoint in B-cell lymphoma and its product functions as a sequence-specific transcriptional repressor. Bcl6 is critical for the differentiation of germinal center B cell. To analyze the function of Bcl6 in B cell development, we used an efficient retroviral transduction system to murine hematopoietic stem cells. We constructed a bicistronic retrovirus expressing the murine Bcl6 and the enhanced green fluorescent protein (EGFP). Lin-Sca-1^+ BM cells (hematopoietic stem cell fraction) were infected with this virus in the presence of SCF and IL-6, and EGFP^+ cells were sorted and injected into the 2.5 Gy irradiated SCID mice or co-cultured on OP-9 stromal cells with or without IL-7. BM cells infected with a control virus (MSCV-EGFP) proliferated and differentiated into B cells and myeloid cells both in vivo and in vitro. BM cells infected with the Bcl6 virus (MSCV-EGFP-Bcl6) differentiated into myeloid cells, but B cell differentiation was impaired. Although myeloid cells expressed high level of EGFP were developed, B cells developed were low or lack in EGFP.On the other hand, hematopoietic stem cells lacking Bcl6 could differentiate into both myeloid and B lymhoid cells. These results suggest that expression of Bcl6 can be used to specify distinct cell fates in the hematopoietic system. Less