Latexin function in the maintenance and regeneration of the hematopoietic system

项目摘要 这项研究的长期目标是制定新的战略，以减轻和保护辐射引起的 通过描述负责增强造血干细胞的分子机制， 细胞（HSC）的自我更新和生存。放射治疗通常不仅会导致急性造血功能障碍， 抑制，而且长期骨髓（BM）损伤。迄今为止，还没有开发出有效的治疗方法 来预防或治疗这些病理后果。增强HSC存活并维持其基因组 辐射后完整性对于保持HSC自我更新功能和保护免受 辐射引起的骨髓损伤。然而，调控HSC存活和自我更新的分子机制 并没有很好的定义。HSC的数量和功能表明了自然变异和潜在的遗传多样性 是一个重要的，但在很大程度上是未知的，在HSC功能的调节机制。Latexin（Lxn） 先前被鉴定为第一个干细胞调节基因，其自然变异对干细胞的生长有负面影响。 不同小鼠品系中的HSC群体大小。在初步研究中，组成型基因切除方法 开发来定义Lxn在正常和辐射应激条件下在HSC和造血中的作用。 结果表明，Lxn失活保护HSC和造血祖细胞（HPC）免受辐射- 诱导细胞死亡，从而减轻急性造血抑制并赋予存活优势。 此外，Lxn敲除小鼠在单次或分次给药后不发生血液学恶性肿瘤。 辐射剂量。在机制上，Lxn在体内失活增加HSC自我更新和存活。在 在分子水平上，我们发表的和初步的工作表明，核糖体蛋白亚基3（Rps 3）是一个新的 Lxn结合蛋白和Lxn过表达抑制Rps 3活性，从而增强辐射敏感性， 毒性此外，人HSC/HPC的数量与Lxn表达水平负相关， 表明Lxn在调节人造血中的潜在作用。这些发现引出了一个假设 Lxn维持稳态HSC和造血，抑制Lxn功能可防止 通过Rps 3依赖性促生存途径的辐射诱导的造血损伤。具体目标是：1） 确定Lxn失活增强HSC存活和自我更新的细胞机制， 赋予辐射防护，2）确定Lxn失活增强Lxn-Rps 3-的分子机制。 NF-kB促存活途径，和3）确定Lxn在减轻人造血细胞毒性中的作用 辐射损伤。这项研究将促进对一个关键但研究不足的机制的理解 参与HSC功能和自我更新的天然调节。通过使用小鼠和人类模型系统 以及最先进的分子和基因组技术，拟议研究的结果可能有助于 开发新的基于机制的治疗策略以防止辐射诱导的BM损伤， 这可能对接受癌症治疗和骨髓移植的患者有益。

PROJECT SUMMARY The long-term goal of this study is to develop new strategies to mitigate and protect radiation-induced hematopoietic injury by delineating the molecular mechanisms responsible for enhancing hematopoietic stem cells (HSC) self-renewal and survival. Radiation therapy commonly results in not only acute hematopoietic suppression but also long-term bone marrow (BM) injury. To date, no effective treatment has been developed to prevent or treat these pathological consequences. Enhancing HSC survival and maintaining their genomic integrity upon radiation are crucial for preservation of HSC self-renewal function and for protection against radiation-induced BM injury. However, the molecular mechanisms for regulating HSC survival and self-renewal are not well defined. HSC number and function demonstrate natural variations, and underlying genetic diversity is an important, yet largely unknown, mechanism involved in the regulation of HSC function. Latexin (Lxn) was previously identified as the first stem cell regulatory gene whose natural variation negatively contributes to the HSC population size in different mouse strains. In preliminary studies, constitutive gene ablation approaches were developed to define the role of Lxn in HSCs and hematopoiesis in normal and radiation stress conditions. Results showed that Lxn inactivation protects HSCs and hematopoietic progenitor cells (HPCs) from radiation- induced cell death, thus mitigating acute hematopoietic suppression and conferring a survival advantage. Moreover, Lxn knockout mice do not develop hematological malignancies following single or fractionated dosages of radiation. Mechanistically, Lxn inactivation in vivo increases HSC self-renewal and survival. At the molecular level, our published and preliminary work showed that ribosomal protein subunit 3 (Rps3) is a novel Lxn-binding protein, and Lxn overexpression inhibits Rps3 activity, thus enhancing radiation sensitivity and toxicity. In addition, the number of human HSCs/HPCs negatively correlates with Lxn expression level, indicating the potential role of Lxn in regulating human hematopoiesis. These findings lead to the hypothesis that Lxn maintains homeostatic HSC and hematopoiesis and inhibition of Lxn function protects against radiation-induced hematopoietic injury via Rps3-dependent prosurvival pathways. Specific aims are to: 1) determine the cellular mechanisms by which Lxn inactivation enhances HSC survival and self-renewal and confers radioprotection, 2) identify the molecular mechanisms by which Lxn inactivation enhances Lxn-Rps3- NF-kB prosurvival pathway, and 3) determine the role of Lxn in mitigating human hematopoietic cell toxicity from radiation injury. This research will advance understanding of a critical but understudied mechanism involved in the natural regulator of HSC function and self-renewal. By using mouse and human model systems and state-of-the-art molecular and genomic techniques, findings from the proposed study may facilitate to the development of novel mechanism-based therapeutic strategy to protect against radiation-induced BM injury, which could be beneficial for the patients receiving cancer therapy and BM transplantation.