Functional and molecular basis of ineffective erythropoiesis in SF3B1-mutant myelodysplastic syndromes

总结 骨髓增生异常综合征（MDS）是一组异质性血液疾病， 以无效和克隆造血为特征，携带影响RNA剪接的体细胞突变 因子最常见的突变剪接因子是SF 3B 1，它是剪接体的核心成分， 在具有环形铁粒幼细胞的MDS（MDS-RS）中优先突变。虽然SF 3B 1突变是 尽管MDS是MDS中最常见的遗传性病变，但对其了解相对较少。我们的不完整 对SF 3B 1突变的理解部分是由于缺乏一个模型系统， 疾病表型，包括环形铁粒幼细胞形成和无效的红细胞生成。因此， 目前尚不清楚SF 3B 1突变如何改变RNA剪接机制，哪些特定的错误剪接基因驱动标志物 疾病表型，以及SF 3B 1突变细胞是否可以被靶向治疗杀死。 在这里，我们建议阐明的功能基础，以及机制和表型的后果， MDS-RS中的SF 3B 1突变。我们的团队由一位具有血液病专业知识的干细胞生物学家组成 建模（Doulatov），具有RNA剪接和功能基因组学专业知识的基础科学家（布拉德利），以及 具有红细胞生成和血红素生物学专长的医生-科学家（Abkowitz）。在初步研究中，我们 产生的MDS-RS患者来源的诱导多能干细胞（iPSC）， 在红细胞分化过程中的表型，确定了特定的错误剪接基因，有助于无效的 红细胞生成，并进行功能基因组筛选，以确定SF 3B 1突变体的分子脆弱性， 细胞我们建议在这些初步研究的基础上进行以下工作：目标1，确定分子结果 SF 3B 1突变对mRNA剪接、稳定性和翻译的影响;目的2，确定环的功能基础 SF 3B 1突变型MDS-RS中铁粒幼细胞形成和无效红细胞生成;目的3， 治疗具有SF 3B 1突变的MDS-RS的机会。这些研究的意义在于， 阐明MDS-RS中SF 3B 1突变的机制和功能后果。健康 相关性是，拟议的工作可能会确定新的机会，治疗MDS的具体目标， SF 3B 1突变细胞。随着MDS发病率的上升和SF 3B 1突变型MDS-RS患者面临终身 输血负担和相关的发病率和死亡率，公共卫生需要开发新的 治疗这种疾病。

SUMMARY The majority of patients with myelodysplastic syndromes (MDS), a heterogeneous group of blood disorders characterized by ineffective and clonal hematopoiesis, carry a somatic mutation affecting an RNA splicing factor. The most commonly mutated splicing factor is SF3B1, a core component of the spliceosome that is preferentially mutated in MDS with ring sideroblasts (MDS-RS). Although SF3B1 mutations are among the most common genetic lesions in MDS, they are nonetheless relatively poorly understood. Our incomplete understanding of SF3B1 mutations is due in part to the absence of a model system that recapitulates hallmark disease phenotypes, including ring sideroblast formation and ineffective erythropoiesis. As a consequence, it is unclear how SF3B1 mutations alter RNA splicing mechanisms, which specific mis-spliced genes drive hallmark disease phenotypes, and whether SF3B1-mutant cells can be killed by targeted therapies. Here, we propose to elucidate the functional basis as well as mechanistic and phenotypic consequences of SF3B1 mutations in MDS-RS. Our team consists of a stem cell biologist with expertise in hematologic disease modeling (Doulatov), a basic scientist with expertise in RNA splicing and functional genomics (Bradley), and a physician-scientist with expertise in erythropoiesis and heme biology (Abkowitz). In preliminary studies, we generated MDS-RS patient-derived induced pluripotent stem cells (iPSCs) that recapitulate hallmark disease phenotypes during erythroid differentiation, identified specific mis-spliced genes that contribute to ineffective erythropoiesis, and performed functional genomic screens to identify molecular vulnerabilities of SF3B1-mutant cells. We propose to build on those preliminary studies as follows: Aim 1, Define the molecular consequences of SF3B1 mutations for mRNA splicing, stability, and translation; Aim 2, Determine the functional basis of ring sideroblast formation and ineffective erythropoiesis in SF3B1-mutant MDS-RS; Aim 3, Identify therapeutic opportunities for treating MDS-RS with SF3B1 mutations. The significance of these studies is that they will elucidate the mechanistic and functional consequences of SF3B1 mutations in MDS-RS. The health relatedness is that the proposed work may identify new opportunities for treating MDS by specifically targeting SF3B1-mutant cells. As the incidence of MDS is rising and patients with SF3B1-mutant MDS-RS face life-long transfusion burdens and associated morbidity and mortality, there is a public health need to develop new therapies for this disorder.