FUNCTION OF THE PROTEINS PU1 AND SPI-B IN B LYMPHOCYTES

淋巴生成是由多能造血干细胞产生淋巴细胞的过程。我感兴趣的是确定两个ETS结构域转录因子PU.1和SPI-B在B淋巴细胞分化和功能中的作用。利用小鼠的基因敲除技术，我们先前已经证明PU1是小鼠胚胎发育所必需的蛋白质。PU.1阴性/阴性小鼠缺乏淋巴系和髓系小鼠细胞，并在宫内死亡。相比之下，SPI-B缺失/缺失小鼠是存活的，但B细胞对抗原的功能反应存在缺陷。为了更具体地剖析SPI-B和PU.1介导的独特和冗余功能，我培育了PU.1+/减号、SPI-B+/减号、PU.1+/减号、SPI-B减号/减号和PU.1减号/减号、SPI-B减号/减号的小鼠。PU.1减/减、SPI-B减/减小鼠表现出与PU.1减/减、SPI-B加/加小鼠相同的表型：它们缺乏所有的淋巴和髓系细胞，并在宫内死亡。有趣的是，PU.1+/-、SPI-B--/-小鼠是存活的，但骨髓和外周淋巴器官中B220/IgM和IgM/IGD的未成熟和成熟B细胞数量显著减少。这些小鼠还表现出成熟B细胞功能的严重缺陷。我的初步数据强烈表明，在蛋白激酶C(PKC)激活之前，SPI-B负性/负性和PU.1+/负性、SPI-B负性/负性小鼠通过B细胞受体(BCR)的信号转导存在缺陷。我建议进行以下实验：(1)鉴定PU.1+/负、SPI-B阴性/阴性小鼠的B细胞发育缺陷；(2)确定SPI-B阴性/阴性、PU.1+/负、SPI-B阴性/阴性小鼠BCR信号缺陷的分子基础。

Lymphopoiesis is the process by which lymphocytes are generated from pluripotent hematopoietic stem cells. I am interested in defining the role of two Ets domain transcription factors, PU.1 and Spi-B, in the differentiation and function of B lymphocytes. Using gene knockout technology in mice, we have previously shown that PU.1 is an essential protein for embryonic development in mice. PU.1 minus/minus mice lack both lymphoid and myeloid mice cells and die in utero. In contrast, Spi-B minus/minus mice are viable but exhibit defects in the functional response of B cells to antigen. To dissect both the unique and redundant functions mediated by Spi-B and PU.1 more specifically, I have generated mice with the genotypes PU.1 plus/minus, Spi-B plus/minus, PU.1 plus/minus, Spi-B minus/minus and PU.1 minus/minus, Spi-B minus/minus. PU.1 minus/minus, Spi-B minus/minus mice exhibit the same phenotype as PU.1 minus/minus, Spi-B plus/plus mice: they lack all lymphoid and myeloid cells and die in utero. Interestingly, PU.1 plus/minus, Spi-B minus/minus mice are viable but exhibit greatly decreased numbers of B220+/IgM+ and IgM+/IgD+ immature and mature B cells in the bone marrow and peripheral lymphoid organs. These mice also exhibit severe defects in mature B cell function. My preliminary data strongly suggest that signaling via the B cell receptor (BCR) is defective in Spi-B minus/minus and PU.1 plus/minus, Spi- B minus/minus mice at a membrane-proximal step prior to the activation of protein kinase C (PKC). I propose experiments to (1) characterize the B cell developmental defect in PU.1 plus/minus, Spi-B minus/minus mice and (2) identify the molecular basis of the BCR signaling defect in Spi-B minus/minus and PU.1 plus/minus, Spi-B minus/minus mice.