Role of the developmental regulator Gon4-like in B lymphopoiesis

描述(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，抵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密控制基因表达和DNA生理性断裂和修复的复杂机制，这是淋巴祖细胞独有的。尽管这些机制的功能非常逼真，但它们可能会受到离散基因损伤的干扰，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促进我们对正常免疫系统生理和由B细胞室引起的疾病的理解至关重要。我们建议的首要目标是对B细胞发育过程中全球控制基因表达的机制有新的认识。已经证实，在B细胞发育过程中，由几个DNA结合蛋白锚定的调控网络主要负责控制基因转录。这个网络实施广泛的基因抑制和激活，从而赋予发育中的祖细胞B血统的身份。然而，在B系DNA结合蛋白下游发挥作用以全局协调基因抑制和激活的因子才刚刚开始被识别。在我们之前的研究中，我们发现了一种新的突变小鼠品系，命名为Justy(仅针对T细胞)，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。致病病变是一种点突变，它显著减少但不会取消一种名为Gon4-like的蛋白质的表达，该蛋白质包含与介导基因转录的表观遗传调节的因子的同源性。基因表达谱显示，类似Gon4的表达减少并不损害B系基因的激活，但确实阻止了编码可对抗B细胞发育的蛋白质的基因的抑制。在这些基因中，有编码因子的基因，这些因子在造血发育途径中具有血统指导作用。基于这些数据，我们假设，Gon4样蛋白是调控网络的关键组成部分，该网络建立了B系基因计划的同一性，同时扼杀了替代的谱系计划，特别是与髓系细胞发育相关的计划。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量化基因表达的方法来开展研究，将Gon4样蛋白整合到控制B细胞发育的调节电路中。为了补充这些研究，我们将使用分子和生化方法来确定Gon4样蛋白的辅助因素，并开始在全基因组范围内确定Gon4样蛋白在基因调控中的作用。这些研究的完成将在我们理解控制造血系命运决定和印记B细胞命运承诺的机制方面开辟新的天地。这些知识将为B细胞发育障碍和免疫缺陷或B细胞祖细胞来源的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.