Role of the developmental regulator Gon4-like in B lymphopoiesis

描述（由申请人提供）：B细胞是免疫系统的重要组成部分：在缺乏这些细胞的情况下，抗感染和建立长期保护性免疫的能力严重受损。B细胞的发育和功能依赖于严格控制基因表达的复杂机制，以及在淋巴祖细胞中独特发生的DNA的生理断裂和修复。尽管这些机制的功能具有显著的保真度，但它们可能被离散的遗传病变扰乱，导致人类免疫功能障碍或淋巴细胞癌。因此，解剖控制B细胞发育的分子途径对于提高我们对正常免疫系统生理学和由B细胞区室引起的疾病的理解至关重要。我们建议的总体目标是获得对B细胞发育过程中全局控制基因表达的机制的新见解。已经确定，在B细胞发育过程中，由几种dna结合蛋白锚定的调控网络主要负责控制基因转录。这个网络强制广泛的基因抑制和激活，从而将B-谱系身份赋予发育中的祖细胞。然而，在b系DNA结合蛋白下游起作用的因子，在全球范围内协调基因抑制和激活，才刚刚开始被确定。在我们之前的研究中，我们发现了一种名为Justy（仅用于T细胞）的新型突变小鼠品系，它携带一种隐性突变，可以消除B细胞的发育，但不会损害小鼠生理的其他主要方面。致病性病变是一个点突变，它会显著减少但不会消除一种叫做gon4样蛋白的表达，这种蛋白与介导基因转录表观遗传调控的因子具有同源性。基因表达谱显示，gon4样表达的减少不会损害B系基因的激活，但会阻止编码可以对抗B细胞发育的蛋白质的基因的抑制。在这些基因中，编码因子在造血发育途径中具有谱系指导作用。基于这些数据，我们假设Gon4-like是调控网络的关键组成部分，该网络建立了b谱系基因程序身份，同时消除了其他谱系程序，特别是与髓细胞发育相关的谱系程序。我们建议使用小鼠遗传工具、细胞培养系统、逆转录病毒基因转移技术和定量基因表达的方法来开展研究，将gon4样细胞整合到控制B细胞发育的调控回路中。为了补充这些研究，我们将使用分子和生化方法来确定Gon4-like的辅助因子，并开始在全基因组范围内定义Gon4-like在基因调控中的作用。这些研究的完成将为我们理解控制造血谱系命运决定和印记承诺对B细胞命运的机制开辟新的领域。这些知识将为B细胞发育障碍与免疫缺陷或B细胞祖源性淋巴样癌的出现之间的关系提供新的见解。

DESCRIPTION (provided by applicant): B cells represent a critical component of the immune system: in the absence of these cells, the ability to fight infections and to establish long-term protective immunity are severely impaired. B cell development and function depend on elaborate mechanisms that tightly control gene expression and the physiologic breakage and repair of DNA that occurs uniquely in lymphoid progenitors. Although these mechanisms function with remarkable fidelity, they can be perturbed by discrete genetic lesions, leading to immune dysfunction or lymphocytic cancers in humans. Thus, dissecting the molecular pathways that control B cell development is critical to advancing our understanding of normal immune system physiology and diseases that arise from the B cell compartment. The overarching objective of our proposal is to gain new insight into the mechanisms that globally control gene expression during B cell development. It has been established that a regulatory network anchored by several DNA-binding proteins is primarily responsible for controlling gene transcription during B cell development. This network enforces widespread gene repression as well as activation, thus imparting a B- lineage identity onto developing progenitors. Yet, the factors that function downstream of B-lineage DNA- binding proteins to globally orchestrate gene repression and activation have only begun to be identified. In our previous studies, we identified a novel mutant mouse strain named Justy (for just T cells), which carries a recessive mutation that abolishes B cell development but does not impair other major aspects of mouse physiology. The causative lesion is a point mutation that dramatically reduces, but does not abolish, expression of a protein called Gon4-like, which contains homology to factors that mediate epigenetic regulation of gene transcription. Gene expression profiling indicated that decreased Gon4-like expression does not impair activation of B-lineage genes, but does prevent the repression of genes encoding proteins that can antagonize B cell development. Among these are genes encoding factors that have lineage-instructive roles in hematopoietic developmental pathways. Based on these data, we hypothesize that Gon4-like is a critical component of the regulatory network that establishes a B-lineage gene program identity while extinguishing alternative lineage programs, particularly those associated with myeloid cell development. We propose to employ mouse genetic tools, cell culture systems, retroviral gene transfer technology and methods for quantifying gene expression to carry out studies that will integrate Gon4-like into the regulatory circuitry the controls B cell development. To complement these studies, we will use molecular and biochemical approaches to identify co-factors for Gon4-like and to begin defining the role of Gon4-like in gene regulation on a genome-wide scale. Completion of these studies will break new ground in our understanding of the mechanisms that control hematopoietic lineage fate decisions and imprint commitment to a B cell fate. Such knowledge will provide novel insights regarding the relationships between impairment of B cell development and the appearance of immunodeficiencies or B cell progenitor-derived lymphoid cancers.