MLL in Hematopoiesis and Leukemia in the Zebrafish Model

MLL 在斑马鱼模型中的造血和白血病中的作用

• 批准号: 8054920
• 负责人: Carolyn A Felix
• 金额: $ 41.63万
• 依托单位: CHILDREN'S HOSP OF PHILADELPHIA
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-04-01 至 2015-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8054920
• 关键词: 11q23; Adult; Affect; Alleles; Anemia; Animal Model; Animals; Antineoplastic Agents; Apoptosis; Automobile Driving; Biological; Blood Cells; Cell Lineage; Cells; Chromosome Band; Clinical; Complementary DNA; Complex; Complication; DNA Sequence Rearrangement; Development; Developmental Process; Disease; Drug resistance; Dysmorphology; Embryo; Embryonic Development; Employee Strikes; Erythrocytes; Erythroid; Future; Gene Expression; Gene Expression Regulation; Gene Targeting; Genes; HRX protein; Hematopoiesis; Hematopoietic; Hematopoietic System; Homeobox; Human; Imagery; In Situ; Infant; Life; Link; Longevity; MLL gene; Malignant - descriptor; Mammals; Messenger RNA; Modeling; Molecular; Morbidity - disease rate; Mus; Myelogenous; Oncogene Proteins; Orthologous Gene; Patients; Pattern; Phenocopy; Phenotype; Poison; Population; Proteins; Regulation; Repression; Role; Stem Cell Development; Time; Tissues; Topoisomerase II; Toxic effect; Transcript; Transcription Regulatory Protein; Transcription factor genes; Transcriptional Activation; Transcriptional Regulation; Transgenic Organisms; Whole Organism; Zebrafish; cdc Genes; cell type; chemotherapy; cofactor; fluorescence imaging; gene repression; hematopoietic tissue; in utero; in vivo; knock-down; leukemia; leukemogenesis; mortality; overexpression; patient population; progenitor; programs; promoter; public health relevance; research study

DESCRIPTION (provided by applicant): Infant leukemias and chemotherapy related leukemias characterized by translocations of the MLL gene at chromosome band 11q23 are devastating, often fatal diseases with unique clinical and biological features. MLL encodes a complex oncoprotein with transcriptional repression and activation functions. The translocations involve many partner genes and generate 5'-MLL-Partner-3' rearrangements, 5'-Partner-MLL-3' rearrangements and MLL haploinsufficiency due to involvement of one allele in the translocation. Unique attributes of zebrafish embryos enable in vivo visualization of normal and abnormal hematopoietic developmental processes in intact animals like no other animal models. Moreover, zebrafish embryos are well suited to model MLL because MLL translocations in infant leukemogenesis originate in utero. Until now, no studies of mll had been done in zebrafish. We cloned the zebrafish mll ortholog and showed high conservation of all of the critical functional domains of human MLL. We found that mll transcripts are maternally supplied to the embryo, expressed during the entire zebrafish lifespan, and detectable in hematopoietic cells and other tissues where Mll is expresed in mice. We demonstrated that mll morpholino knockdown phenocopies the external phenotype, apoptosis and anemia of Mll-/- mice. We made the striking observations that the resulting mll depletion caused not only reduced homeobox cofactor and altered cell cycle gene expression, but also overexpression and underexpression of many hematopoietic genes in different blood cell compartments, suggesting new links of mll to previously unknown targets. Furthermore, the changes in blood cell gene expression caused profound blood cell dysmorphologies. While overexpressed genes in the precursor/myeloid compartment featured lmo2, scl, cmyb, ikaros, rag2 and gata1, reduced expression of gata1 and other red cell genes was detected in the erythroid fraction, linking the anemia from mll depletion to deregulation of an entire erythroid program. This leads to the hypothesis that MLL has profound multi-lineage roles in the developmental control of the hematopoietic system, that temporal and cell-type specific regulation of gene expression by MLL including repression and activation is required for orderly specification of hematopoietic progenitor and stem cell development, and that loss of MLL causes ectopic and asynchronous overexpression and underexpression of blood cell lineage genes and ineffective development of the hematopoietic system. This project endeavors to investigate this hypothesis by exploiting whole organism studies and cellular and molecular studies on cells from whole organisms that are only possible in zebrafish to pinpoint the cells where MLL is most important and when MLL translocations first become transforming. PUBLIC HEALTH RELEVANCE: MLL is a critically important gene for blood cell development, abnormalities of which called translocations have a significant impact on morbidity and mortality in the infant population affected with leukemia and in the patient population affected with leukemia as a complication of certain anti-cancer drugs. This project will exploit the tremendous potential of zebrafish to understand the dynamics of how normal blood cell development is regulated by MLL in space and time from the earliest developmental timepoints in the living embryo, and how the same dynamics are deregulated in disease. The exploitation of zebrafish to model the functions of human MLL in the regulation of normal and malignant blood cell development will streamline future inroads to new molecularly targeted therapies for patients with MLL leukemia.

描述（由申请人提供）：以染色体带 11q23 处 MLL 基因易位为特征的婴儿白血病和化疗相关白血病是具有独特临床和生物学特征的毁灭性且通常致命的疾病。 MLL 编码具有转录抑制和激活功能的复杂癌蛋白。易位涉及许多伙伴基因并产生 5'-MLL-Partner-3' 重排、5'-Partner-MLL-3' 重排以及由于易位中涉及一个等位基因而导致的 MLL 单倍体不足。斑马鱼胚胎的独特属性使得完整动物中正常和异常造血发育过程的体内可视化成为其他动物模型所无法比拟的。此外，斑马鱼胚胎非常适合 MLL 模型，因为婴儿白血病发生中的 MLL 易位起源于子宫内。到目前为止，还没有在斑马鱼中进行过 MLL 的研究。我们克隆了斑马鱼 MLL 直向同源物，并显示出人类 MLL 的所有关键功能域的高度保守性。我们发现，mll 转录本由母源提供给胚胎，在斑马鱼的整个生命周期中表达，并且在小鼠中表达 Mll 的造血细胞和其他组织中可检测到。我们证明了 mll 吗啉代敲低表型复制了 Mll-/- 小鼠的外部表型、细胞凋亡和贫血。我们进行了惊人的观察，即由此产生的 mll 耗竭不仅导致同源盒辅因子减少和细胞周期基因表达改变，而且还导致不同血细胞区室中许多造血基因的过度表达和表达不足，这表明 mll 与以前未知的靶标有新的联系。此外，血细胞基因表达的变化导致了严重的血细胞畸形。虽然前体/骨髓区室中过度表达的基因包括 lmo2、scl、cmyb、ikaros、rag2 和 gata1，但在红细胞部分中检测到 gata1 和其他红细胞基因的表达减少，这将 mll 耗竭导致的贫血与整个红细胞程序失调联系起来。这导致了这样的假设：MLL 在造血系统的发育控制中具有深远的多谱系作用，MLL 对基因表达的时间和细胞类型特异性调节（包括抑制和激活）是造血祖细胞和干细胞发育的有序规范所必需的，并且 MLL 的缺失会导致血细胞谱系的异位和异步过表达和表达不足 基因和造血系统发育不良。该项目致力于通过利用整个生物体研究以及对来自整个生物体的细胞的细胞和分子研究来研究这一假设，这些研究只有在斑马鱼中才能实现，以查明 MLL 最重要的细胞以及 MLL 易位首次发生转化的时间。 公共卫生相关性：MLL 是血细胞发育的一个极其重要的基因，其异常（称为易位）对患有白血病的婴儿群体以及患有某些抗癌药物并发症的白血病患者群体的发病率和死亡率具有重大影响。该项目将利用斑马鱼的巨大潜力来了解 MLL 如何在活体胚胎最早发育时间点的空间和时间上调节正常血细胞发育的动态，以及在疾病中相同的动态如何解除调节。利用斑马鱼来模拟人类 MLL 在正常和恶性血细胞发育调节中的功能，将简化未来针对 MLL 白血病患者的新分子靶向治疗的进展。