PLC?s in B cell biology and autoimmunity

描述（由申请方提供）：早期B细胞发育和晚期B细胞成熟分别由前B细胞受体（BCR）和BCR发出的信号调节。在成熟过程中，B细胞对自身抗原的耐受性通过克隆缺失、受体编辑和无反应性来建立，这些都由BCR发出的信号控制。扭曲的前BCR/BCR信号传导通常导致缺陷的B细胞发育、B细胞耐受性的破坏以及免疫缺陷和自身免疫性疾病的发展。来自前BCR/BCR的调节B细胞发育和耐受性的信号尚未完全了解。磷脂酶C3（PLC 3）是一种重要的脂质酶，参与前BCR/BCR信号传导。PLC 3有两种亚型，PLC 31和PLC 32。PLC 32缺陷型小鼠存活，早期和晚期B发育受损。我们最近的数据发现PLC 32在轻链位点的激活、自身反应性受体的编辑和B细胞无反应性的诱导中起重要作用。PLC 31缺陷导致妊娠中期的早期胚胎死亡，排除了对其在B细胞发育中作用的分析。然而，我们对PLC 31缺陷杂合子（PLC 31 PLC 32-/-）的PLC 32缺陷小鼠的研究表明PLC 31在B发育中也起重要作用。我们最近已经产生了小鼠，其中PLC 31基因可以有条件地失活。利用具有遗传修饰的PLC 31和PLC 32基因的小鼠，我们处于有利地位以进一步研究PLC 31/PLC 32在B淋巴细胞生成中的单独和组合作用，包括耐受性建立，以及PLC 3s调节该过程的机制。我们假设PLC 31和PLC 32在前BCR/BCR介导的功能和建立B细胞耐受性中起重要作用。为了验证我们的假设，我们提出了三个具体目标。我们将1）确定PLC 31的作用以及PLC 31和PLC 32在前BCR介导的早期B细胞发育、IgH链的等位基因排斥、IgL链基因座的活化和B细胞库的形成中的组合作用，2）确定PLC 31和PLC 32在BCR介导的B细胞成熟、受体编辑和B细胞中无反应性的诱导中的单独和组合作用，3）研究PLC 31和PLC 32在pre-BCR/BCR信号传导中的上下游通路。拟进行的研究旨在了解两种PLC 3亚型在B淋巴细胞生成中的作用，特别是耐受建立，以及它们传递前BCR/BCR信号的机制。这项研究可能为自身免疫性疾病的分子发病机制提供新的线索，并有助于确定特定治疗的靶点。

DESCRIPTION (provided by applicant): Early B cell development and late B cell maturation are regulated by signals emanating from the pre-B cell receptor (BCR) and BCR, respectively. During maturation, B cell tolerance to self-antigens is established through clonal deletion, receptor editing and anergy, which are controlled by signals emanating from the BCR. Distorted pre-BCR/BCR signaling often results in defective B cell development, breakdown of B cell tolerance and development of immunodeficiency and autoimmune diseases. Signals from the pre-BCR/BCR that regulate B cell development and tolerance are not fully understood. Phospholipase C3 (PLC3) is an important lipid enzyme involved in pre-BCR/BCR signaling. PLC3 has two isoforms, PLC31 and PLC32. PLC32-deficient mice are viable and have impaired early and late B development. Our recent data find that PLC32 plays an important role in activation of light chain loci, editing of self-reactive receptors and induction of B cell anergy. PLC31 deficiency results in early embryonic death at midgestation, precluding analysis of its role in B cell development. However, our studies of PLC32-deficient mice that are heterozygous for PLC31-deficiency (PLC31PLC32-/-) indicate that PLC31 also plays an important role in B development. We have recently generated mice in which the PLC31 gene can be conditionally inactivated. With the mice that have genetically modified PLC31 and PLC32 genes, we are well-positioned to further study the individual and combined roles of PLC31/PLC32 in B lymphopoiesis, including tolerance establishment, and the mechanism by which both PLC3s regulate the process. We hypothesize that both PLC31 and PLC32 play an important role in pre- BCR/BCR-mediated functions and in establishing B cell tolerance. To test our hypothesis, we propose three specific aims. We will 1) determine the role of PLC31 and combined roles of PLC31 and PLC32 in pre- BCR-mediated early B cell development, allelic exclusion of IgH chain, activation of the IgL chain loci, and formation of the B cell repertoire, 2) determine the individual and combined roles of PLC31 and PLC32 in BCR- mediated B cell maturation, receptor editing and induction of anergy in B cells, and 3) study the upstream and downstream pathways of PLC31 and PLC32 during pre-BCR/BCR signaling. The proposed research seeks to understand the roles for the two PLC3 isoforms in B lymphopoiesis, especially tolerance establishment, and the mechanism by which they relay the signals from the pre-BCR/BCR. The study may provide new clues to the molecular pathogenesis of autoimmune diseases and help identify targets for specific therapies.