Uncovering the role for Msi2 in hematopoietic stem cells

描述(申请人提供)：通过从对称细胞分裂到不对称细胞分裂，造血干细胞(HSC)的数量被小心地保持。由遗传和表观遗传机制组成的维持正常HSCs的复杂程序可能会在造血障碍和恶性肿瘤中变得失调。骨髓增生异常综合征(MDS)是一组克隆性起源的异质性疾病，表现为造血分化缺陷。结合最近在MDS遗传格局中的发现，这种疾病的病因学被认为是由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止的，或者为什么自我更新被改变。MSI家族中的RNA结合蛋白在胚胎和组织干细胞功能、神经细胞分化和细胞命运的决定中起着重要的作用。最近的研究表明MSI2是HSC功能的调节者，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，该方案结合了高通量测序UV-交联型免疫沉淀来确定全局RNA靶点(HITS-CLIP)，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对翻译的监管如何改变了几条发育途径。最近还发现，MSI2在“低风险”患者的MDS中表达失调，低于正常水平，并在表现出MSI2表达升高的“高风险”患者中表达。这项建议利用NUP98-Hoxd13 MDS小鼠模型和新的获得和丧失功能的MSI2小鼠模型来研究HSC内MDS的初始阶段。我们认为，MSI2的失调有助于造血疾病的生物学，因此对这些机制的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.