Neurofibromatosis Type 1 Gene Regulates Myelopoiesis

1 型神经纤维瘤病基因调节骨髓细胞生成

• 批准号: 6613714
• 负责人: David W Clapp
• 金额: $ 48.43万
• 依托单位: INDIANA UNIV-PURDUE UNIV AT INDIANAPOLIS
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-04-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6613714
• 关键词: biological signal transduction; bone marrow; cell differentiation; cell growth regulation; cell proliferation; chronic myelogenous leukemia; clinical research; colony stimulating factor; gene expression; gene mutation; genetic regulation; genetically modified animals; guanine nucleotide binding protein; guanosine triphosphate; guanosinetriphosphatase activating protein; hematopoietic stem cells; laboratory mouse; myeloid stem cell; neoplasm /cancer genetics; neurofibromatosis; neurofibromatosis type 1 protein /gene; pediatric neoplasm /cancer; protooncogene; tissue /cell culture; tumor suppressor genes

DESCRIPTION (provided by applicant): Mutatons in the NF1 tumor suppressor gene cause neurofibromatosis type 1 (NF-1). NF1 encodes a GTPase activating protein (GAP) for p21 ras (Ras) called neurofibromin. Neurofibromin converts p21 ras from its active GTP to its inactive GDP bound conformation. Individuals with NFl have a propensity to acquire benign and malignant tumors. Additionally, children with NFl are predisposed to juvenile myelomonocytic leukemia (JMML). A hallmark of myeloid progenitors (CFU-GM) from JMML bone marrow cells is their propensity to hyperproliferate in response to low doses of the growth factor granulocyte macrophage colony stimulating factor (GM-CSF). Homozygous disruption of Nfl is lethal in utero; however we found that murine Nf1 -deficient fetal hematopoletic cells show an abnormal pattern of CFU-GM growth and hyperactivation of Ras effectors in response to multiple growth factors, including GM-CSF and stem cell factor (SCF), the ligand for the c-kit receptor tyrosine kinase. C-kit is encoded by the murine dominant white spotting locus, W). Since the W and Nfl loci appeared to function along a common developmental pathway, mice with mutations at both loci were generated. We found that haploinsufficiency of Nfl partially rescued the mast cell and coat color defects in W41 mice. These data offered genetic evidence that haploinsufficiency at Nfl modulates cell fates in vitro and in vivo in two lineages that are affected in individuals with NFl. The results support the emerging concept that heterozygous inactivation of tumor suppressor genes may have important biological effects.While loss of neurofibromin increases p21 ras activity in specific cell lineages, identification of alterations in distinct p21 ras effector pathways that control proliferation and survival in NF1-deficient cells is incomplete and critical for understanding disease pathogenesis. Most previous studies argue that loss of neurofibromin results in increased activation of the classical p21 ras-Raf-Mek-ERK pathway. However, we have preliminary data to support an alternative biochemical model where the growth advantage of Nfl1-deficient cells is mediated through increased signals from p21 ras to the small Rho GTPase, Rac2, a Rac isoform expressed only in hematopoietic cells. We propose studies to examine how activation of p21 ras and Rac isoforms cooperate to alter the biology of Nfl +/- mast cells and Nf 1 -/- stem and myeloid progenitor cells utilizing mice with genetic mutations in these loci.

描述（由申请人提供）：NF1肿瘤抑制基因中的突变导致1型神经纤维瘤病（NF-1）。 NF1 编码 p21 ras (Ras) 的 GTP 酶激活蛋白 (GAP)，称为神经纤维蛋白。神经纤维蛋白将 p21 ras 从其活性 GTP 转化为其非活性 GDP 结合构象。患有 NF1 的个体有患良性和恶性肿瘤的倾向。此外，患有 NF1 的儿童易患幼年型粒单核细胞白血病 (JMML)。 JMML 骨髓细胞的骨髓祖细胞 (CFU-GM) 的一个标志是，它们在低剂量的生长因子粒细胞巨噬细胞集落刺激因子 (GM-CSF) 的作用下倾向于过度增殖。 Nfl 的纯合破坏在子宫内是致命的；然而，我们发现，缺乏 Nf1 的小鼠胎儿造血细胞表现出异常的 CFU-GM 生长模式和 Ras 效应器对多种生长因子的过度激活，包括 GM-CSF 和干细胞因子 (SCF)（c-kit 受体酪氨酸激酶的配体）。 C-kit 由小鼠显性白斑基因座 W) 编码。由于 W 和 Nfl 基因座似乎沿着共同的发育途径发挥作用，因此产生了两个基因座均发生突变的小鼠。我们发现 Nfl 的单倍体不足部分挽救了 W41 小鼠的肥大细胞和毛色缺陷。这些数据提供了遗传证据，表明 Nfl 的单倍体不足在体外和体内调节受 NF1 个体影响的两个谱系的细胞命运。这些结果支持了新出现的概念，即肿瘤抑制基因的杂合失活可能具有重要的生物学效应。虽然神经纤维蛋白的丢失会增加特定细胞谱系中的 p21 ras 活性，但控制 NF1 缺陷细胞增殖和存活的不同 p21 ras 效应途径的改变的鉴定是不完整的，并且对于了解疾病发病机制至关重要。之前的大多数研究认为，神经纤维蛋白的缺失会导致经典 p21 ras-Raf-Mek-ERK 通路激活增加。然而，我们有初步数据支持另一种生化模型，其中 Nfl1 缺陷细胞的生长优势是通过 p21 ras 到小 Rho GTPase、Rac2（一种仅在造血细胞中表达的 Rac 亚型）信号增加来介导的。我们提出研究，利用这些位点具有基因突变的小鼠，研究 p21 ras 和 Rac 亚型的激活如何协同改变 Nfl +/- 肥大细胞和 Nf 1 -/- 干细胞和骨髓祖细胞的生物学特性。