The functional role of DDX41 in myelodysplastic syndromes

DDX41 在骨髓增生异常综合征中的功能作用

• 批准号: 10750070
• 负责人: Honghao Bi
• 金额: $ 7.63万
• 依托单位: NORTHWESTERN UNIVERSITY AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-30 至 2026-09-29
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10750070
• 关键词: Acute Myelocytic Leukemia; Affect; Alleles; Apoptosis; Binding Sites; Biogenesis; Biological Assay; Body Weight; Bone Marrow; CD34 gene; Cell Death; Cell Lineage; Cells; Characteristics; Complete Blood Count; DNA Structure; Data; Defect; Development; Dysmyelopoietic Syndromes; Erythroblasts; Erythroid Cells; Erythropoiesis; Flow Cytometry; Functional disorder; G-Quartets; Genes; Genome; Germ-Line Mutation; Guanine; Hematologic Neoplasms; Hematopoiesis; Hematopoietic; Hematopoietic System; Hematopoietic stem cells; Human; In Vitro; Knock-out; Knockout Mice; Lead; Mediating; Modeling; Molecular; Mus; Mutate; Mutation; Pathogenesis; Pathway interactions; Patients; Reporting; Research; Ribosomal Proteins; Ribosomes; Risk; Role; Running; Site; Small Nucleolar RNA; Somatic Mutation; Spleen; Stress; Susceptibility Gene; Symptoms; TP53 gene; Technology; Testing; Up-Regulation; Zebrafish; cytopenia; experimental study; helicase; in vivo; loss of function; mouse model; novel; novel therapeutics; peripheral blood; response; targeted treatment

Project Summary Myelodysplastic syndromes (MDS) are a group of hematologic malignancies characterized by clonal hematopoiesis, one or more cytopenias, and increased risks to transform into acute myeloid leukemia (AML). Multiple mutations have been identified to be associated with MDS. One of these mutations occurs on DEAD- box helicase 4 (DDX41) gene. At least 70 DDX41 germline or somatic mutations have been reported, making DDX41 one of the most frequently mutated MDS predisposition genes. Germline DDX41 mutations lead to its loss of function whereas somatic mutations often produce hypomorphic changes. Recent studies in zebrafish showed that knockout of DDX41 induces increased R-loop accumulation and aberrant hematopoiesis. Another research using conditional DDX41 knockout mice reported that DDX41 biallelic mutations disrupt snoRNA biogenesis and lead to apoptosis in hematopoietic cells. These and other studies started to shed lights on the mechanisms of DDX41 mutated pathogenesis of MDS. However, it still remains unknown how loss of DDX41 in hematopoietic cells causes apoptosis and what lineages are most sensitive to its deficiency. Therefore, it is essential to dissect the molecular and cellular mechanisms of DDX41’s functions, which could be helpful to develop targeted therapy for DDX41 mutated MDS. G-quadruplexes (G4) are four-stranded, noncanonical secondary DNA structures formed in guanine-rich sequences. We showed in our preliminary study that loss of DDX41 led to aberrant upregulation of G4 in the hematopoietic system. We further revealed that G4 is enriched during erythropoiesis. G4 accumulation due to DDX41 deficiency severely disrupted erythropoiesis with less effects in other lineages in vitro and ex vivo. Importantly, we validated these in vitro findings and revealed that the lethality of hematopoietic-specific DDX41 knockout mice is likely due to the defects in erythropoiesis. Our preliminary mechanistic studies also revealed that DDX41 deficiency-mediated G4 upregulation in erythroid cells compromised the expression of various ribosome proteins that led to p53-dependent apoptosis in erythroid cells. Based on these data, we hypothesize that DDX41 deficiency in MDS leads to G4 accumulation and defects in ribosome biogenesis, which induces p53-mediated cell death specifically in erythroid cells. To test our hypothesis, we propose three specific aims. Aim 1 will focus on the study of the functions of DDX41 in various lineages of hematopoietic cells by generating lineage specific DDX41 knockout mice. In aim 2, we will investigate how DDX41 regulates the accumulation of G4 in erythropoiesis. Aim 3 will focus on the mechanistic studies on DDX41-G4-ribosomal biogenesis-p53 pathway. Successful completion of our proposed research will provide novel mechanisms of DDX41’s functional role in normal and abnormal hematopoiesis, which will be impactful for the development of novel therapies for DDX41 mutation-related hematologic malignancies.

项目概要 骨髓增生异常综合征（MDS）是一组以克隆性为特征的血液系统恶性肿瘤 造血功能下降、一种或多种血细胞减少以及转化为急性髓系白血病 (AML) 的风险增加。 多种突变已被确定与 MDS 相关。这些突变之一发生在 DEAD- 框解旋酶 4 (DDX41) 基因。已报道至少 70 个 DDX41 种系或体细胞突变，使得 DDX41 是最常突变的 MDS 易感基因之一。种系 DDX41 突变导致其 功能丧失，而体细胞突变通常会产生亚型变化。斑马鱼的最新研究 研究表明，DDX41 的敲除会导致 R 环积累增加和造血异常。其他 使用条件性 DDX41 敲除小鼠的研究报告称，DDX41 双等位基因突变会破坏 snoRNA 生物发生并导致造血细胞凋亡。这些研究和其他研究开始揭示 DDX41突变MDS发病机制。然而，目前仍不清楚 DDX41 的丢失是如何发生的。 造血细胞会导致细胞凋亡，以及哪些谱系对其缺陷最敏感。因此，它是 对于剖析 DDX41 功能的分子和细胞机制至关重要，这可能有助于 开发针对 DDX41 突变 MDS 的靶向治疗。 G-四链体 (G4) 是四链的、非规范的 在富含鸟嘌呤的序列中形成二级DNA结构。我们在初步研究中表明， DDX41 导致造血系统中 G4 的异常上调。我们进一步透露G4被丰富了 红细胞生成期间。 DDX41 缺乏导致的 G4 积累严重扰乱了红细胞生成， 对体外和离体其他谱系的影响。重要的是，我们验证了这些体外研究结果并揭示了 造血特异性 DDX41 敲除小鼠的致死率可能是由于红细胞生成缺陷所致。我们的 初步机制研究还表明，DDX41 缺陷介导的红系细胞中 G4 上调 损害各种核糖体蛋白的表达，导致红系细胞中 p53 依赖性细胞凋亡。 基于这些数据，我们假设 MDS 中 DDX41 缺陷导致 G4 积累和缺陷 核糖体生物发生，特别是在红系细胞中诱导 p53 介导的细胞死亡。为了检验我们的假设， 我们提出三个具体目标。目标1将重点研究DDX41在不同谱系中的功能 通过生成谱系特异性 DDX41 敲除小鼠来产生造血细胞。在目标 2 中，我们将研究如何 DDX41 调节红细胞生成过程中 G4 的积累。目标3将侧重于机制研究 DDX41-G4-核糖体生物发生-p53 途径。成功完成我们提议的研究将提供 DDX41 在正常和异常造血中的功能作用的新机制，这将对 DDX41 突变相关血液恶性肿瘤新疗法的开发。