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: 8606829
• 负责人: Carolyn A Felix
• 金额: $ 38.46万
• 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 2016-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8606829
• 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.

描述（由申请人提供）：以染色体带11 q23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疾病，通常是致命性疾病。MLL编码具有转录抑制和激活功能的复杂癌蛋白。易位涉及许多配偶体基因，并且由于易位中涉及一个等位基因而产生5 '-MLL-配偶体-3'重排、5 '-配偶体-MLL-3'重排和MLL单倍不足。斑马鱼胚胎的独特属性使得在完整动物中正常和异常造血发育过程的体内可视化成为可能，这是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直系同源物，并显示出高度保守的所有关键功能域的人MLL。我们发现，mll转录物由母体提供给胚胎，在整个斑马鱼寿命期间表达，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吗啉代敲低表型模仿了Mll-/-小鼠的外部表型、凋亡和贫血。我们做了惊人的观察，结果mll的消耗不仅导致减少同源框辅因子和改变细胞周期基因的表达，但也过度表达和低表达的许多造血基因在不同的血细胞室，提示新的链接mll以前未知的目标。此外，血细胞基因表达的变化导致了严重的血细胞畸形。虽然在前体/髓样区室中过表达的基因以lmo 2、scl、cmyb、ikaros、rag 2和gata 1为特征，但在红细胞部分中检测到gata 1和其他红细胞基因的表达减少，将mll耗竭引起的贫血与整个红细胞程序的失调联系起来。这导致以下假设：MLL在造血系统的发育控制中具有深刻的多谱系作用，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特化所需的，MLL的缺失导致血细胞谱系基因的异位和异步过表达和低表达，以及血细胞谱系基因的无效发育。造血系统该项目致力于通过利用整个生物体研究以及对整个生物体细胞的细胞和分子研究来研究这一假设，这些研究仅在斑马鱼中才有可能确定MLL最重要的细胞以及MLL易位首次转化的细胞。