Biologic and Therapeutic Consequences of Distinct Hotspot SF3B1 Mutations in MDS

项目摘要 骨髓增生异常综合征(MDS)是最常见的克隆性血液疾病，其特征是 骨髓因异常干细胞而占优势，血细胞生产受损。患有疾病的患者 MDS合并贫血、感染、出血和进行性疾病所致的多器官衰竭。 结果很差，治疗也不充分。开发新疗法的关键是更好地理解 导致这些疾病的基因突变。大约一半的MDS患者存在剪接体突变 在这些基因中，SF3B1是最常见的突变。突变体SF3B1是新构型的，破坏RNA 剪接来产生我们所说的JEM(富含突变剪接小体细胞的剪接连接)，尽管如何 JEM产生MDS表型尚不清楚。SF3B1基因突变被认为是一种良好的预后标志 MDS。然而，在sf3b1突变的病理特征和临床转归上有相当大的异质性。 MDS仍未得到解释。由于这种异质性导致了有效的疾病管理，其原因需要 为了更好地被理解。我们建议的前提是，理解SF3B1突变MDS的关键是 研究不同SF3B1突变之间的差异。该基因在热点区域发生突变，影响多个 氨基酸，我们的初步数据显示，特定的突变与不同的临床特征有关，RNA 拼接模式和对治疗的反应。我们也有数据表明SF3B1突变会扰乱新陈代谢 可能影响铁粒母细胞贫血和代谢易损性的具体途径，我们已经开发出新的 用于研究这些过程的SF3B1突变造血的人体模型。拟议中的工作 结合了内科科学家(道尔顿博士)的专业知识，他专门研究细胞生物学、遗传学和人类 疾病的细胞模型和专门从事骨骼临床研究的临床研究员(德泽恩博士) 骨髓衰竭疾病。我们将共同追求三个目标：1)描述私人和 MDS热点SF3B1突变间共有JEM。我们将使用原始MDS样本的RNA-seq和 同基因人类细胞模型绘制不同SF3B1突变的RNA剪接图谱并将其用作 了解它们扰乱的途径。2)确定不同的SF3B1突变在 人类造血细胞的生长和分化。我们将使用原代MDS样本和同基因细胞 确定铁粒母细胞性贫血、细胞适应性和SF3B1突变的代谢易损性的机制 造血细胞。3)明确MDS中不同SF3B1突变的临床病理特征。利用 来自NHLBI国家MDS研究的高质量数据，我们将确定如何区分热点SF3B1突变 通过多因素分析影响MDS的病理和临床特征。圆满完成这些目标 有望揭示RNA剪接的病理生理机制，重新定义疾病分类和预后， 并改进MDS的治疗方法。

Project Summary The myelodysplastic syndromes (MDS) are the most common clonal blood disorders, characterized by dominance of the bone marrow by abnormal stem cells and impairment of blood cell production. Patients with MDS suffer from combinations of anemia, infection, bleeding, and multiorgan failure from progressive disease. Outcomes are poor, and treatments are inadequate. Key to developing new treatments is better understanding of the mutations which create these diseases. Roughly half of MDS patients have mutations in spliceosome genes, and of these, SF3B1 is the most commonly mutated. Mutant SF3B1 is neomorphic, disrupting RNA splicing to create what we refer to as JEMs (splice Junctions Enriched in Mutant-spliceosome cells), though how JEMs produce MDS phenotypes is unknown. SF3B1 mutation is regarded as a favorable prognostic marker in MDS. Yet, there is considerable heterogeneity in the pathologic features and clinical outcomes of SF3B1-mutant MDS that remains unexplained. As this heterogeneity beguiles effective disease management, its causes need to be better understood. The premise of our proposal is that a key to understanding SF3B1-mutant MDS is to study the differences between distinct SF3B1 mutations. This gene is mutated in hotspots affecting multiple amino acids, and our preliminary data show that specific mutations associate with distinct clinical features, RNA splicing patterns, and responses to therapy. We also have data that SF3B1 mutations disrupt metabolism in specific ways that likely affect sideroblastic anemia and metabolic vulnerabilities, and we have developed novel human models of SF3B1-mutant hematopoiesis with which to study these processes. The proposed work combines the expertise of a physician-scientist (Dr. Dalton) who specializes in cell biology, genetics, and human cell modeling of disease with that of a clinical investigator (Dr. DeZern) who specializes in clinical studies of bone marrow failure disorders. Together, we will pursue three aims: 1) Characterize the landscape of private and shared JEMs among hotspot SF3B1 mutations in MDS. We will use RNA-seq of primary MDS samples and isogenic human cell models to map the RNA splicing landscape of different SF3B1 mutations and use this as a ‘way in’ to understanding the pathways they disrupt. 2) Establish the role of distinct SF3B1 mutations in the growth and differentiation of human hematopoietic cells. We will use primary MDS samples and isogenic cells to determine mechanisms of sideroblastic anemia, cell fitness, and metabolic vulnerability in SF3B1-mutant hematopoietic cells. 3) Define the clinicopathologic features of distinct SF3B1 mutations in MDS. Leveraging the high-quality data from the NHLBI National MDS Study, we will determine how distinct hotspot SF3B1 mutations affect pathologic and clinical features of MDS through multivariate analysis. Successful completion of these aims promises to reveal pathophysiologic mechanisms of RNA splicing, redefine disease classification and prognosis, and improve treatment approaches in MDS.