Regulation and function of nuclear envelope proteins in myelopoiesis and leukemia

描述（由申请人提供）：中性粒细胞和单核/巨噬细胞是先天免疫系统的重要组成部分，具有根除细菌和某些真菌感染的功能。这些细胞在发育和功能上都具有相同的特征，但它们也有独特的核特征，使它们与其他白细胞区别开来：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，但一种称为层粘胶蛋白B受体（LBR）的内核包膜蛋白表达不足导致中性粒细胞减少，这是Pelger-Hukt异常的特征，巨噬细胞表达某些称为a型层粘胶蛋白的核包膜蛋白和中间丝蛋白，这些蛋白在其他造血细胞中基本上是缺乏的。产生这些髓细胞不规则核特征的分子机制具有临床意义，因为核结构异常的中性粒细胞与骨髓增生异常有关，骨髓增生异常常发展为髓性白血病，并且在白血病和淋巴瘤中都发现了核包膜蛋白的异常表达。本研究的长期目标是确定髓细胞发育中核包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细胞发育及其获得关键功能中的作用。为了实现这些目标，具体的目标是：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，这些靶点在调节发育中的中性粒细胞和巨噬细胞的核结构变化中起重要作用；3)操纵髓系祖细胞中NE蛋白和a型层蛋白的表达，并确定对髓系细胞增殖、分化和功能的影响。为了实现这些目标，将对小鼠Gabp与Lbr基因启动子的相互作用进行表征，并生成缺乏Gabp功能的新型小鼠髓系祖细胞，并对其进行中性粒细胞和巨噬细胞分化分析。将提供或抑制核膜或a型层粘胶蛋白表达的载体引入髓系祖细胞，并评估其对分化、形态成熟和功能反应的影响。这些研究将有助于理解髓细胞发育过程中不同核包膜蛋白表达模式的控制机制，确定这些表达模式对髓细胞分化的重要性，并有助于解释为什么造血恶性肿瘤经常导致髓细胞核结构异常。

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.