MicroRNA Regulation of Stem Cell Self-renewal

细胞内存在调节造血干细胞(HSC)自我更新的机制。自我更新能力 限制在正常干细胞中是维持组织完整性所必需的，并负责 受伤后的再生。然而，当它被异常细胞获得时，可能会产生自我更新的癌症。 对治疗无效的干细胞。了解自我更新的机制对于 治疗扩增造血干细胞以及根除血癌的恶性根源。 与信使核糖核酸的表达相比，微核糖核酸的表达可以准确地标志发育的历史和/或阶段。 造血干细胞的发育经历了一个特征明确的分步分化过程，并逐渐失去了自我 更新产能。破坏microRNA生物发生关键酶DICER，完全消融干细胞 活动。因此，我们假设，在调节这些关键步骤和 某些microRNAs的表达可能与自我更新能力有关。两种互补的方法 被用来识别这种特定的microRNA。通过扫描已知的基因的3‘UTR区 我们发现miR-150通过靶向c-Myb发挥其功能。另外， 使用原代干细胞及其非更新即刻进行microRNA表达谱分析 子代细胞。根据microRNA表达谱，我们鉴定了miR-99b-let-7e-miR-125a 在体内长期移植后显著扩大造血室的集落。 建议详细了解这些microRNA物种在调节HSC自我更新中的作用 有两个明确的目标。1.利用miR-150基因敲除小鼠确定miR-150在HSC功能中的作用。2.定义 MiR-99b-let-7e-125a簇在促进HSC自我更新中的作用及其候选者评估 分子靶标。这些目标将通过组合使用转基因技术来实现。 在斯卡登博士的实验室中，可以随时获得小鼠品系和适当的体内和体外检测方法。 相关性(请参阅说明)： 这项拟议的研究有望发现促进HSC自我更新的microRNA调节剂。这样的microRNA 将为HSC的调控提供新的范式。它们还将用作研究工具，以发现更多 赋予自我更新表型的分子途径和网络，不仅对正常的造血干细胞，而且对 白血病干细胞。

Cell intrinsic mechanisms exist to regulate hematopoietic stem cell (HSC) self-renewal. Self-renewal ability confined to the normal stem cells is essential for maintaining tissue integrity and is responsible for regeneration after injury. When acquired by aberrant cells, however, it could produce a self-renewing cancer stem cell that is refractory to treatments. Understanding the mechanisms of self-renewal is important for therapeutic expansion of HSCs as well as for eradicating the malignant roots of blood cancers. Contrasting to mRNA expression, microRNA expression faithfully marks developmental history and/or stage. HSCs develop through a well characterized step-wise differentiation process with a gradual loss of the self- renewing capacity. Disruption of the microRNA biogenesis key enzyme, Dicer, completely ablated stem cell activity. We thus hypothesized that specific microRNAs are required in regulating these key steps and the expression of some microRNAs may correlate with the ability to self-renew. Two complementary approaches were used to identify such specific microRNAs. By scanning the 3'UTR regions of genes known to be important for hematopoiesis, we identified that miR-150 exerted its function by targeting c-Myb. Additionally, microRNA expression profiling was performed using primary stem cells and their non-renewing immediate descendant cells. Based on the microRNA expression profile, we identified the miR-99b-let-7e-miR-125a cluster which dramatically expanded the hematopoietic compartment after long term transplantation in vivo. propose to gain detailed understanding of these microRNA species in regulating HSC self-renewal through two specific aims. 1. Determine the role of miR-150 in HSC function using miR-150 knockout mice. 2. Define the role of the miR-99b-let-7e-125a cluster in enhancing HSC self-renewal and assess its candidate molecular targets. These aims will be achieved through the combinational use of genetically engineered mouse strains and the appropriate in vivo and in vitro assays readily available in Dr. Scadden's laboratory. RELEVANCE (Seeinstructions): The proposed study promises the discovery of microRNA regulators for HSC self-renewal. Such microRNAs will provide new paradigms for HSC regulation. They will also serve as research tools to uncover additional molecular pathways and networks that confer the self-renewal phenotype, not only to normal HSCs, but also to leukemia stem cells.