Studies on ontogenic significance of PLC signaling systems.

磷脂酶C(PLC)催化磷脂酰肌醇-4，5-二磷酸(PIP_2)生成肌醇-1，4，5-三磷酸(IP_3)和二酰甘油(DAG)，这种催化活性受受体激活的控制。众所周知，这两个产物，IP_3和DAG，介导细胞内钙释放和蛋白激酶C的激活。在PLC亚型中，本研究以PLC-γ2的生物学功能为研究重点，采用两种不同的基因敲除策略建立了PLC-γ2功能缺失的小鼠模型。1)利用基因打靶的方法，成功地获得了异源携带pLc-γ-2基因的小鼠，其催化X区被NEO取代。然而，纯合子小鼠是胚胎致死的，并在E8.5岁时死亡。5)用干扰素调节的Cre重组酶诱导PLC-γ2基因被烧毁。新生鼠PLC-γ-2功能丧失后，成熟的常规B细胞和腹膜B-L细胞成员减少，体外对bcr刺激和体内对胸腺非依赖性II型AGS免疫的反应有缺陷。相比之下，T细胞发育和TCR介导的增殖是正常的。这些结果表明，PLC-γ2是bcr信号通路的重要组成部分，是促进B细胞发育所必需的。

Phospholipase C (PLC) hydrolyzes phosphatidylinositol-4,5-bisphosphate (PIP_2) to generate inositol-1,4,5-trisphosphate (IP_3) and diacylglycerol (DAG), and this catalytic activity is controlled upon receptor activation. It is well understood that these two products, IP_3 and DAG, mediate the calcium release from intracellular stores and protein kinase C activation. Among PLC isoforms, this study focused on biological function of PLC-γ2, Mice with loss of PLC-γ2 function were produced using two different gene knockout strategies. Following results were obtained from this research project.1) Using gene-targeting approach, mice heterogeneously harboring PLC-γ2 gene of which a catalytic X region was replaced by neo, were successfully produced. The homozygous mice, however, were embryonic lethal and died at 〜E8.5.2) The PLC-γ2 gene was inducibly ablated by using IFN-regulated Cre recombinase. Mice with neonatally induced loss of PLC-γ2 function displayed reduced members of mature conventional B cells and peritoneal B l cells and defective responses in vitro to BCR stimulation and in vivo to immunization with thymusindependent type-II Ags. In contrast, T cell development and TCR-mediated proliferation were normal. These results indicate that PLC-γ2 is a critical component of BCR signaling pathways and is required to promote B cell development.