Uncovering the role for Msi2 in hematopoietic stem cells

描述（由申请人提供）：造血干细胞（HSC）数量通过从对称到不对称的细胞分裂切换来小心地保持。维持正常造血干细胞的遗传和表观遗传机制组成的复杂程序在造血系统疾病和恶性肿瘤中可能变得失调。骨髓增生异常综合征（MDS）的特征是一组克隆衍生的异质疾病，表现出造血分化缺陷。结合MDS遗传学领域的最新发现，这种疾病的病因被认为是由HSC或早期髓系祖细胞驱动的。因此，细胞命运决定的失调，包括不对称和对称细胞分裂的平衡，可以解释某些谱系是如何被阻断的，或者为什么自我更新被改变。Msi家族的RNA结合蛋白已被证明在生殖和组织干细胞功能、神经细胞分化和细胞命运决定中，在对称和非对称细胞分裂之间的转换中起重要作用。最近的研究表明MSI2是HSC功能的调节因子，本研究利用MSI2条件敲除和功能获得的方法来分析MSI2在控制不对称分裂、自我更新和细胞命运决定中的确切作用。此外，该建议结合高通量测序uv交联免疫沉淀来识别全局RNA靶点（HITS-CLIP），这将用于阐明造血细胞中MSI2的直接机制。此外，我们的全球遗传方法已经揭示了翻译调节如何改变几种发育途径。MSI2在“低风险”患者中表达低于正常水平，在“高风险”患者中表达升高，最近也被证明在MDS中表达失调。本研究利用NUP98-HOXD13 MDS小鼠模型结合新型功能增减MSI2小鼠模型，研究HSC内MDS的初始阶段。我们认为MSI2失调有助于造血疾病的生物学，因此对这些机制的更深入了解将提供额外的治疗方法。

DESCRIPTION (provided by applicant): Hematopoietic stem cell (HSC) numbers are carefully maintained by switching from symmetric to asymmetric cell divisions. A complex program made of genetic and epigenetic mechanisms that maintain normal HSCs can become dysregulated in hematopoietic disorders and malignancies. Myelodysplastic syndromes (MDS) are characterized as a clonally derived set of heterogeneous diseases demonstrating defective hematopoietic differentiation. Taken together with recent discoveries in the genetic landscape of MDS, the etiology of this disease is considered to be driven by an HSC or an early myeloid progenitor. Thus, dysregulation of cell fate decisions including the balance of asymmetric and symmetric cell division could explain how certain lineages are blocked or why self-renewal is altered. RNA binding proteins in the Msi family have been shown to be important for the switch between symmetric and asymmetric cell division in germ and tissue stem cell function, neural cell differentiation and cell fate determination. Recent studies have implicated MSI2 as a regulator of HSC function and this proposal utilizes Msi2 conditional knockouts and gain of function approaches to dissect the precise role for MSI2 in controlling asymmetric division, self-renewal and cell fate determination. Moreover, this proposal incorporates high throughput sequencing UV-crosslinking immunoprecipitation to identify global RNA targets (HITS-CLIP) that will be used to elucidate the direct mechanism for MSI2 in hematopoietic cells. Furthermore, our global genetic approaches have already uncovered how regulation of translation alters several developmental pathways. MSI2 has also been recently shown to be dysregulated in MDS within "low- risk" patients, expressing below normal levels and within "high-risk" patients demonstrating elevated MSI2 expression. This proposal utilizes the NUP98-HOXD13 MDS murine model combined with novel gain and loss of function MSI2 mouse models to study the initial stages of MDS within the HSC. We suggest that MSI2 dysregulation contributes to the biology of hematopoietic disorders and thus a deeper understanding of these mechanisms will provide additional therapeutic approaches.