Manipulating the Stem Cell Epigenome to Improve Bone Marrow Transplantation

摘要 骨髓移植(BMT)是最成熟的干细胞治疗方法，已被广泛应用。 在临床环境中成功应用了近50年。然而，确定适当捐赠者材料的来源 对于许多成年患者来说，骨髓移植仍然是一个限制因素。脐带血(UCB)已成为 越来越受欢迎的捐赠者来源，因为新生儿的造血细胞具有免疫性 更天真。这降低了移植物抗宿主病(GvHD)的风险，因此患者和捐赠者也是如此。 不一定要在免疫上兼容。UCB扩大了患者接受BMT的范围，特别是在 少数族裔患者。尽管脐带血移植有多种优势，但它与 移植和免疫重建延迟，导致更大的感染和移植物排斥反应的风险 与成人捐献者的骨髓或外周血移植相比。这主要与较低的 长期造血再分化的功能单位--造血干细胞的含量 BMT，在单个脐带血单位内。这些限制限制了脐带血移植的应用。 为了扩大脐带血HSC的数量或提高其体外效力，人们做出了巨大的努力，但这些研究 在很大程度上都不成功。在这里，我们提出了一种新的方法来解决这个长期存在的问题。在……里面 小鼠模型，我们发现了一种阻止染色质介导的HSC自我更新沉默的机制 通过拮抗表观遗传调节因子JARID2，JARID2招募多梳抑制复合体2 (PrC2)催化H3K27me3的抑制性组蛋白修饰。在这里，我们将利用这些成果来 确定JARID2的瞬时抑制是否可以用于增加体外可移植的HSCs的数量， 并改善BMT。具体地说，我们假设JARID2抑制将阻止PRC2介导的 表观遗传抑制自我更新的基因表达程序，从而扩大细胞池 具有功能上的再繁殖潜力。我们将正式调查这一战略，具体目标如下： 确定抑制JARID2是否可以扩大具有功能的骨髓再生细胞 移植和定义机制 我们的方法有三个方面：(A)确定JARID2的瞬时抑制是否可以扩大池 在有功能的HSC中，(B)确定PRC2介导的HSC抑制所需的JARID2的蛋白结构域 自我更新基因，以及(C)识别调节JARID2表达的反式激活因子 剥削。SIRE-II机制(PAS-15-168)致力于支持新的研究方向 他们的早期阶段。与这一目标一致，翻译BMT研究是一个全新的研究领域 我们的实验室。但凭借我们在造血干细胞表观遗传调控方面的经验以及获得协作专业知识的机会，我们 准备为这一重大的临床问题做出新的贡献。实现我们的研究目标 将为未来的高影响力翻译研究提供基础，与PAS-15-168的目标一致。

ABSTRACT Bone marrow transplantation (BMT) is the best-established stem cell therapy, and has been used successfully in clinical settings for almost 50 years. However, identifying sources of appropriate donor material for BMT continues to be a limiting factor for many adult patients. Umbilical cord blood (UCB) has become an increasingly popular donor source because the hematopoietic cells from newborn babies are immunologically more naïve. This reduces the risk of graft-versus-host-disease (GvHD), and therefore the patient and donor do not have to be as immunologically compatible. UCB has extended patient access to BMT, especially for patients of racial and ethnic minorities. Despite multiple advantages of UCB transplant, it is associated with delayed engraftment and immune reconstitution, leading to a greater risk of infections and graft reject as compared to bone marrow or peripheral blood grafts from adult donors. This is primarily related to the lower content of hematopoietic stem cells (HSCs), the functional units of long-term hematopoietic repopulation in BMT, within individual cord blood units. These caveats have limited the application of UCB transplantation. There are intense efforts to expand UCB HSC numbers or increase their potency ex vivo, but these studies have been largely unsuccessful. Here, we propose a novel method to resolve this long-standing problem. In murine models, we identified a mechanism that prevents chromatin-mediated silencing of HSC self-renewal genes by antagonizing the epigenetic regulator JARID2, which recruits Polycomb Repressive Complex 2 (PRC2) to catalyze the repressive histone modification of H3K27me3. Here, we will leverage these results to determine if transient inhibition of JARID2 can be used to increase the number of transplantable HSCs ex vivo, and improve BMT. Specifically, we hypothesize that JARID2 inhibition will prevent PRC2-mediated epigenetic repression of self-renewal gene expression programs, thereby expanding the pool of cells with functional repopulation potential. We will formally investigate this strategy in the following Specific Aim:  Determine if inhibition of JARID2 can expand functional repopulating cells for bone marrow transplant and define the mechanisms There are three prongs to our approach; (A) Determine if transient inhibition of JARID2 can expand the pool of functional HSCs, (B) Identify the protein domains of JARID2 required for PRC2-mediated repression of HSC self-renewal genes, and (C) Identify trans-activating factors that regulate JARID2 expression for translational exploitation. The SHINE-II mechanism (PAS-15-168) is dedicated to supporting new research directions in their early stages. Consistent with this goal, translational BMT research is a completely new area of study for our lab. But with our experience in epigenetic regulation of HSCs and access to collaborative expertise, we are poised to make novel contributions to this significant clinical problem. Achievement of our research objectives will provide the basis for future high-impact translational research, consistent with the goals of PAS-15-168.