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.

项目概要/摘要 该提案的目标是了解正常的发育程序如何塑造遗传和 急性髓系白血病（AML）的表观遗传景观。 AML 可以发生在生命的任何阶段，但突变 导致 AML 的因素在儿童期和成年期之间有所不同，尤其是当人们将幼儿与成年期进行比较时 成年人。例如，Flt3 内部串联重复 (FLT3ITD) 突变在青少年和青少年中很常见。 成人 AML，但在婴儿和幼儿期 AML 中很少见。同样，MLL 易位存在于大多数 婴儿 AML 中常见，但成人 AML 中很少见。这些观察结果表明 FLT3ITD 可能会改变成人 造血祖细胞比胎儿祖细胞更有效，MLL易位可能会改变胎儿 祖细胞比成年祖细胞更有效。在初步研究中，我们发现 Flt3ITD 和 Flt3ITD/Runx1 协同突变导致造血干细胞 (HSC) 耗竭和骨髓祖细胞 在成人生命阶段而非胎儿阶段的扩张。 FLT3ITD 在胎儿、新生儿中激活 STAT5 信号转导 和成年祖细胞，但直到出生后约 2 周才诱导靶基因表达的变化。这 数据表明，胎儿和新生儿祖细胞受到保护，不会发生转化，因为它们不 能够表达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 胎儿祖细胞的景观抑制FLT3ITD靶基因的激活。在平行研究中，我们测试了是否 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 诱导几乎在所有测试的小鼠中引起 AML。成人诱导不会导致 AML 接受测试的小鼠（现在已进行 6 个月的随访）。这些结果表明成年祖细胞抵抗转化 MLL-ENL 就像胎儿祖细胞抵抗 FLT3ITD 的转化一样。需要进一步的工作来理解 决定个体突变何时以及如何能够发挥作用的顺式和反式调控元件 转换。在目标 1 中，我们建议精确描述从胎儿到成人转录的转变 使用 Drop-seq 和 ATAC-seq 技术开发 HSC 和骨髓祖细胞的计划。在目标 2 中， 我们建议测试 Flt3ITD 和合作的 Flt3ITD/Runx1 突变是否具有发育背景- 对基因调控和白血病发生的具体影响。我们将测试 Flt3ITD 和 Flt3ITD 的增强剂是否 Flt3ITD;Runx1靶基因在发育过程中具有年龄特异性的可接近和不可接近模式， 以及成人特异性异时转录因子是否是 AML 形成所必需的。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如何与基因突变相互作用以导致 恶性肿瘤，可能有可能在治疗上针对这些相互作用。