TEMPORAL CHANGES IN MECHANISMS OF HSC SELF-RENEWAL AND MYELOID LEUKEMOGENESIS

HSC 自我更新和髓样白血病发生机制的暂时变化

• 批准号: 9905414
• 负责人: Jeffrey Alan Magee
• 金额: $ 38.13万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-04-01 至 2022-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9905414
• 关键词: ATAC-seq; Acute Myelocytic Leukemia; Adolescent; Adult; Adult Acute Myeloblastic Leukemia; Age; Alleles; Birth; Blood; Child; Childhood; Childhood Acute Myeloid Leukemia; Chromatin; DNA Sequence Alteration; Data; Development; Enhancers; Epigenetic Process; Gene Activation; Gene Expression; Gene Expression Regulation; Genes; Genetic; Genetic Transcription; Goals; Hematopoietic stem cells; Individual; Infant; Life; Malignant Neoplasms; Mus; Mutation; Myelogenous; Myeloid Leukemia; Neonatal; Pattern; Regulatory Element; Shapes; Signal Transduction; Stat5 protein; Stem Cell Development; Technology; Testing; Tetracyclines; Therapeutic; Transcription Coactivator; Work; design; droplet sequencing; early childhood; fetal; follow-up; hematopoietic stem cell self-renewal; improved; leukemogenesis; loss of function; postnatal development; progenitor; programs; stem cells; transcription factor; transcriptome

PROJECT SUMMARY/ABSTRACT The goal of this proposal is to understand how normal developmental programs shape the genetic and epigenetic landscapes of acute myeloid leukemia (AML). AML can occur at any stage of life yet the mutations that cause AML differ between childhood and adulthood, especially when one compares young children to adults. For example, the Flt3 Internal Tandem Duplication (FLT3ITD) mutation is common in adolescent and adult AML, but it is rare in infant and early childhood AML. Likewise, MLL translocations are found in a majority of infant AML, yet they are rare in adult AML. These observations suggest that FLT3ITD may transform adult hematopoietic progenitors more efficiently than fetal progenitors, and MLL translocations may transform fetal progenitors more efficiently than adult progenitors. In preliminary studies, we discovered that Flt3ITD and cooperating Flt3ITD/Runx1 mutations caused hematopoietic stem cell (HSC) depletion and myeloid progenitor expansion in adult, but not fetal, stages of life. FLT3ITD activated STAT5 signal transduction in fetal, neonatal and adult progenitors, yet it did not induce changes in target gene expression until ~2 weeks after birth. The data suggest that fetal and neonatal progenitors are protected from transformation because they are not competent to express FLT3ITD target genes. Either they lack key transcriptional co-activators, or the epigenetic landscape of fetal progenitors suppresses FLT3ITD target gene activation. In parallel studies, we tested whether a tetracycline-inducible MLL-ENL allele transforms fetal progenitors more efficiently than adult progenitors. Fetal MLL-ENL induction caused AML in almost all mice tested. Adult induction did not cause AML in any of the mice tested (now at 6 months follow-up). These results suggest that adult progenitors resist transformation by MLL-ENL much like fetal progenitors resist transformation by FLT3ITD. Further work is needed to understand the cis- and trans-regulatory elements that determine when and how individual mutations are competent to transform. In Aim 1, we propose to precisely characterize the transition from fetal to adult transcriptional programs in developing HSCs and myeloid progenitors using Drop-seq and ATAC-seq technologies. In Aim 2, we propose to test whether Flt3ITD and cooperating Flt3ITD/Runx1 mutations have developmental context- specific effects on gene regulation and leukemogenesis. We will test whether enhancers for Flt3ITD and Flt3ITD;Runx1 target genes have age-specific patterns of accessibility and inaccessibility during development, and whether adult-specific, heterochronic transcription factors are necessary for AML formation. In Aim 3, we will test whether MLL-ENL has developmental context-specific effects on gene regulation and leukemogenesis. If we can understand how normal developmental programs interact with genetic mutations to cause malignancies, it may be possible to target these interactions therapeutically.

项目摘要/摘要 这项建议的目标是了解正常的发育计划如何塑造基因和 急性髓系白血病(AML)的表观遗传学景观。急性髓细胞白血病可以发生在生命的任何阶段，但突变 导致AML的原因在儿童和成人之间是不同的，特别是当人们将幼儿与 成年人。例如，Flt3内部串联复制(Flt3ITD)突变在青少年和 成人AML，但在婴幼儿AML中少见。同样，MLL易位在大多数情况下也被发现 婴儿AML，但在成人AML中很少见。这些观察结果表明，Flt3ITD可能会使成人 造血祖细胞比胎儿祖细胞更有效，MLL易位可能会改变胎儿 祖辈比成年祖辈更有效率。在初步研究中，我们发现Flt3ITD和 协同Flt3ITD/RUNX1突变导致造血干细胞(HSC)耗竭和髓系祖细胞 在成人阶段，但不是胎儿阶段。Flt3ITD激活胎儿、新生儿STAT5信号转导 和成体祖细胞，但直到出生后约2周才引起靶基因表达的变化。这个 数据表明，胎儿和新生儿的祖细胞受到保护，不会发生变化，因为他们没有 能表达Flt3ITD靶基因。它们要么缺乏关键的转录共激活因子，要么缺乏表观遗传学 胎儿祖细胞的景观抑制了FLT3ITD靶基因的激活。在平行研究中，我们测试了 四环素诱导的MLL-ENL等位基因比成年祖细胞更有效地转化胎儿祖细胞。 胎儿MLL-ENL诱导可引起几乎所有受试小鼠的急性髓系白血病。成人诱导没有引起任何一种急性髓系白血病 小鼠进行了测试(现在进行了6个月的随访)。这些结果表明成年祖细胞抵抗转化。 通过MLL-enl，就像胎儿祖细胞一样，抵抗Flt3ITD的转化。还需要进一步的工作才能理解 顺式和跨式调控元件，决定了个体突变何时以及如何有能力 变形。在目标1中，我们建议精确地描述从胎儿到成人转录的转变。 使用Drop-seq和atac-seq技术开发造血干细胞和髓系祖细胞的方案。在目标2中， 我们建议测试Flt3ITD和协同的Flt3ITD/RUNX1突变是否具有发育背景- 对基因调控和白血病发生的特殊作用。我们将测试Flt3ITD和 Flt3ITD；RUNX1靶基因在发育过程中具有特定年龄的可及性和不可及性模式， 以及AML的形成是否需要成人特有的、异时性的转录因子。在目标3中，我们 将测试MLL-enl是否对基因调控和白血病发生具有发育背景特异性影响。 如果我们能够理解正常的发育程序是如何与基因突变相互作用而导致 恶性肿瘤，有可能以这些相互作用为靶点进行治疗。