Regulation and function of nuclear envelope proteins in myelopoiesis and leukemia

说明(申请人提供)：中性粒细胞和单核/巨噬细胞是先天免疫系统的基本组成部分，其功能是根除细菌和某些真菌感染。这些细胞既有发育和功能特征，也有区别于其他白细胞的独特核特征：中性粒细胞有分叶状核，单核细胞有不规则的肾形核。这些改变的核结构是如何形成的尚不清楚，但核内层被蛋白B受体(LBR)的表达不足会导致具有Pelger-Hukt异常特征的中性粒细胞低密度，巨噬细胞表达某些核被膜蛋白和称为A-型层蛋白的中间丝蛋白，这是其他造血细胞基本缺乏的。产生这些髓系细胞不规则核特征的分子机制是临床上感兴趣的，因为核结构异常的中性粒细胞与骨髓发育不良相关，通常进展为髓系白血病，核膜蛋白的异常表达在白血病和淋巴瘤中都被发现。这项建议的长期目标是确定在发育中的髓系细胞中驱动核膜蛋白独特表达模式的转录机制，并确定这些蛋白在调节髓系细胞发育和获得关键功能方面所起的作用。为了实现这些目标，具体目的是：1)确定转录因子GA结合蛋白(GABP)在调节LBR表达中的功能；2)确定GABP的其他靶点，这些靶点在发育中的中性粒细胞和巨噬细胞的核结构变化中发挥重要作用；3)调控髓系祖细胞中NE蛋白和A型层粘连蛋白的表达，并确定对髓系细胞增殖、分化和功能的影响。为了达到这些目的，我们将鉴定小鼠Gabp与LBR基因启动子的相互作用，并将产生新的缺乏Gabp功能的小鼠髓系祖细胞，并对其进行中性粒细胞和巨噬细胞分化的分析。提供或抑制核膜或A-型层粘连蛋白表达的载体将被引入髓系祖细胞，并将评估其对分化、形态成熟和功能反应的影响。这些研究将有助于了解髓系细胞发育过程中控制不同核膜蛋白表达模式的机制，确定这些表达模式对髓系细胞分化的重要性，并有助于解释为什么恶性血液病常常导致髓系细胞核结构的异常。 与公众健康相关：这项建议的目标是确定导致两种血细胞形成独特核结构特征的分子机制，这两种细胞是天然免疫的关键，中性粒细胞和巨噬细胞，并确定核膜蛋白在协调其核特征中所起的作用。这些研究与公众健康相关，因为它们将提供更好的理解，为什么核结构异常和核膜蛋白表达中断与血液系统恶性肿瘤有关，包括危及生命的骨髓发育不良和髓系白血病。

DESCRIPTION (provided by applicant): Neutrophils and monocytes/macrophages are essential components of the innate immune system and function to eradicate bacterial and certain fungal infections. These cells share both developmental and functional features, but they also have unique nuclear features that distinguish them from other white blood cells: neutrophils have a lobulated nucleus and monocytes bear an irregular, kidney-shaped nucleus. How these altered nuclear structures form is unclear, but deficient expression of an inner nuclear envelope protein called the lamin B receptor (LBR) causes neutrophil hypolobulation characteristic of Pelger-Hukt anomaly, and macrophages express certain nuclear envelope proteins and intermediate filament proteins called A-type lamins that are essentially lacking in other hematopoietic cells. The molecular mechanisms that create irregular nuclear features of these myeloid cells are of clinical interest because neutrophils with abnormal nuclear structure are associated with myelodysplasias that often progress to myeloid leukemias, and aberrant expression of nuclear envelope proteins has been identified in both leukemias and lymphomas. The long-term objective of this proposal is to identify the transcriptional mechanisms that drive the unique expression patterns of nuclear envelope proteins in developing myeloid cells, and to identify the roles that these proteins play in regulating myeloid cell development and their acquisition of critical functions. To achieve these objectives, the specific aims are to i) define the functions of a transcription factor, GA- binding protein (GABP), in regulating the expression of LBR, ii) identify additional targets of GABP that play important roles in orchestrating changes in nuclear structure of developing neutrophils and macrophages, and iii) manipulate the expression of NE proteins and A-type lamins in myeloid progenitors and identify effects on myeloid cell proliferation, differentiation and function. To achieve these aims, interactions of mouse Gabp with the Lbr gene promoter will be characterized, and novel mouse myeloid progenitors that lack Gabp function will be generated and analyzed for neutrophil and macrophage differentiation. Vectors that provide for, or inhibit, nuclear envelope or A-type lamin protein expression will be introduced into myeloid progenitors, and effects on differentiation, morphologic maturation and functional responses will be assessed. These studies will provide an understanding of the mechanisms that control different nuclear envelope protein expression patterns in developing myeloid cells, identify the importance of these expression patterns to myeloid differentiation, and help to explain why hematopoietic malignancies often result in aberrant nuclear structures in myeloid cells. PUBLIC HEALTH RELEVANCE: The objective of this proposal is to identify the molecular mechanisms that cause unique nuclear structural features to form in two blood cells that are critical to innate immunity, neutrophils and macrophages, and define the roles that nuclear envelope proteins play in orchestrating their nuclear features. These studies are relevant to public health because they will provide a better understanding of why aberrant nuclear structure and disrupted expression of nuclear envelope proteins are associated with hematologic malignancies, including life-threatening myelodysplasias and myelogenous leukemias.