Manipulating the Stem Cell Epigenome to Improve Bone Marrow Transplantation

摘要 骨髓移植（BMT）是最成熟的干细胞疗法， 在临床上成功应用了近50年。然而，确定适当的捐赠材料来源， 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）已成为一种 越来越受欢迎的供体来源，因为来自新生儿的造血细胞在免疫学上是 更天真。这降低了移植物抗宿主病（GvHD）的风险，因此患者和供体 不需要在免疫学上兼容。UCB扩大了患者获得BMT的机会，特别是对于 少数民族和种族的病人。尽管UCB移植有多种优点，但它与以下因素有关： 延迟植入和免疫重建，导致感染和移植物排斥的风险更大， 与来自成人供体的骨髓或外周血移植相比。这主要是因为， 造血干细胞（HSC）的含量，长期造血重建的功能单位， BMT，在单个脐带血单位内。这些问题限制了脐血移植的应用。 有大量的努力来扩大UCB HSC数量或增加其体外效力，但这些研究 基本上都不成功。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 在小鼠模型中，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JARID 2来调节基因，JARID 2招募Polycomb抑制复合物2 （PRC 2）催化H3 K27 me 3的抑制性组蛋白修饰。在这里，我们将利用这些结果， 确定JARID 2的瞬时抑制是否可用于增加离体可移植HSC的数量， 改善BMT。具体地说，我们假设JARID 2抑制将阻止PRC 2介导的 自我更新基因表达程序的表观遗传抑制，从而扩大细胞库 具有功能性繁殖潜力。我们将在以下具体目标中正式研究这一策略： 确定抑制JARID 2是否可以扩增骨髓功能性再生细胞 移植和定义机制 我们的方法有三个方面：（A）确定JARID 2的瞬时抑制是否可以扩大库 （B）鉴定PRC 2介导的HSC抑制所需的JARID 2的蛋白结构域 （C）鉴定调节JARID 2表达的反式激活因子，用于翻译 剥削SHINE-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相一致，翻译BMT研究是一个全新的研究领域， 我们的实验室但是，凭借我们在HSC表观遗传调控方面的经验和获得合作专业知识的机会， 准备为这个重要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转化研究提供基础，符合PAS-15-168的目标。

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.