FUNCTION OF N-MYC PROTEIN IN LYMPHOCYTE DIFFERENTIATION

N-MYC 蛋白在淋巴细胞分化中的功能

• 批准号: 2101774
• 负责人: BARBARA A MALYNN
• 金额: $ 14.38万
• 依托单位: IMMUNE DISEASE INSTITUTE, INC.
• 依托单位国家: 美国
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-07-01 至 1998-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2101774
• 关键词: B lymphocyte; T lymphocyte; apoptosis; cell line; cell nucleus; chimeric proteins; cytoplasm; developmental genetics; gene expression; gene mutation; gestational age; hematopoiesis; hematopoietic growth factor; immunofluorescence technique; in situ hybridization; laboratory mouse; lymphocyte proliferation; messenger RNA; mutant; nucleic acid probes; nucleic acid sequence; protooncogene; temperature sensitive mutant; tissue /cell culture; transcription factor

N-myc is a member of a family of proto-oncogenes that encode related but distinct nuclear proteins. Myc genes are putative transcription factors that are thought to function in the regulation of gene expression in the context of cell growth and differentiation. However, the exact function of myc genes is unknown. Each myc gene is associated with a unique tissue-specific pattern of spontaneously arising tumors that partially reflects the expression pattern in normal development. The finding that a null mutation of N-myc when homozygous in the germline of the mouse is embryonic lethal suggests that N-myc plays a unique physiological role during development. N-myc is highly regulated during B lymphocyte development. Pre-B cells express both c-myc and N-myc. The expression of c-myc and N-myc mRNA is induced in normal pre-B cells by treatment with the pre-B cell specific growth factor IL-7; at this stage, regulation is mediated by releasing a block to transcriptional elongation. When cells mature to the B cell stage, transcriptional initiation of N-myc is down-regulated, while c-myc continues to be expressed. Together, these findings suggest that N-myc has a specific function in the early stages of B cell development. We hypothesize that N-myc is required for the expansion of precursor B cells either by promoting their growth, inhibiting their death, and/or preventing their terminal differentiation. The goal of these studies is to define precisely the function of N-myc during B lymphocyte development and how it relates to c-myc function. How N-myc may be involved in determination of other hematopoietic lineages will also be examined. The exact stages within B lymphocyte and T lymphocyte differentiation when N-myc is expressed will be determined. This expression will be correlated with expression of other stage-specific features within that lineage. The affect of a null N-myc mutation on development of committed and uncommitted progenitor cells will be determined. If a maturational block in B cell development is found, the differentiation stage at which it occurs will be defined and characterized. Transformed and nontransformed cell lines will be derived in order to determine how expression of other stage-specific genes are affected by lack of N-myc expression. The response of these cells to growth factor and mitogenic signals will be tested. A novel approach is presented for the derivation of immortalized cell lines that represent B cell differentiation stages and that retain full differentiative capacity is presented. Using "hit and run" gene targeting techniques, the sequences within each of the myc genes that determine their unique functions within lymphocyte differentiation will be determined. Finally, we will determine if N-myc may function during hematopoiesis by induction of apoptosis or modulation of c-myc-induced apoptosis. Besides providing insights into the molecular mechanisms underlying lymphocyte development, these studies may also yield revelations about myc gene function generally during embryogenesis and how transcription factors function in developmental processes. Furthermore, an understanding of how myc genes function in normal development may reveal how inappropriate expression leads to oncogenesis.

N-myc是原癌基因家族的一员，编码相关的，但 不同的核蛋白 Myc基因是公认的转录因子 被认为在调节基因表达中起作用， 细胞生长和分化的背景。 然而，确切的功能 myc基因的表达是未知的。每个myc基因都与一个独特的 自发性肿瘤的组织特异性模式， 反映了正常发育中的表达模式。 的发现 当在小鼠的生殖系中纯合时，N-myc的无效突变是 胚胎致死表明，N-myc发挥独特的生理作用， 在发展过程中。 N-myc在B淋巴细胞发育过程中受到高度调节。 前b细胞 同时表达c-myc和N-myc。 c-myc和N-myc mRNA的表达均高于正常对照组。 在正常前B细胞中通过用前B细胞特异性 生长因子IL-7;在这个阶段，调节是通过释放 阻断转录延伸。 当细胞成熟为B细胞时 N-myc转录起始下调，c-myc转录起始下调， 继续表达。 总之，这些发现表明，N-myc 在B细胞发育的早期阶段具有特定的功能。 我们 假设N-myc是前体B细胞扩增所必需的 通过促进它们的生长，抑制它们的死亡，和/或 阻止它们的终末分化。 这些研究的目的是 明确N-myc在B淋巴细胞发育中的作用 以及它与c-myc功能的关系。 N-myc如何参与 还将检查其他造血谱系的确定。 B淋巴细胞和T淋巴细胞分化的确切阶段 将确定N-myc何时表达。 这个表达式将是 与其他阶段特异性特征的表达相关， 脉 N-myc基因缺失突变对恶性肿瘤发生的影响 并确定未定型的祖细胞。 如果一个成熟 在B细胞发育中发现了一个阻滞，在这个分化阶段， 将被定义和描述。 变换和 将衍生未转化的细胞系，以确定如何 其他阶段特异性基因的表达受到N-myc缺乏的影响 表情 这些细胞对生长因子和促有丝分裂因子的反应 信号将被测试。 提出了一种新的推导方法 代表B细胞分化阶段的永生化细胞系 并保留完整的微分能力。 使用"命中 并运行"基因靶向技术"， 决定淋巴细胞内独特功能的基因 差异化将被确定。 最后，我们将确定N-myc 在造血过程中可能通过诱导细胞凋亡或调节 c-myc诱导的凋亡。 除了提供对潜在的分子机制的见解， 淋巴细胞发育，这些研究也可能揭示 myc基因通常在胚胎发生过程中发挥作用， 因素在发展过程中发挥作用。 此外， 了解myc基因在正常发育中的功能可能会揭示 不适当的表达是如何导致肿瘤发生的