The HMGA1 Chromatin Regulator in Hematopoietic Stem Cells with Aging

背景：本研究的目的是阐明由高表达的蛋白质调控的表观遗传机制。 流动性组A1（Hmga 1）染色质重塑蛋白在造血干细胞（HSC）， 确定它是如何随着年龄的增长而变化的。Hmga 1通过“打开”染色质调节基因表达， 将转录复合物募集到DNA上。虽然很明显，表观基因组的改变和 转录网络随着HSC的衰老而发生，驱动衰老表型的关键因素仍然很差， 明白在这里，我们专注于Hmga 1染色质调节器作为一个关键的调节器的“年轻”HSC功能。 我们的科学前提是基于以下初步结果：1）Hmga 1表达富集于 HSC并随衰老而下降，2）Hmga 1整体缺失的小鼠发展出早衰表型， 3)Hmga 1缺陷HSC概括了一个老化表型的子集，包括向前 体外培养B淋巴样细胞，体内连续骨髓移植（BMT）再生功能差。 4)在已发表的工作中，我们发现HMGA 1：A）在人类中维持去分化的多能状态， B）通过诱导干细胞转录网络增强胚胎干细胞的重编程， 体细胞向多能干细胞转化。5)最近，我们发现了一个新的角色 HMGA 1通过放大Wnt/β-catenin作为肠干细胞区室的主要调节因子， 发信号。6)我们小组发表的工作也表明，HMGA 1表达失调， 导致造血细胞的分化和克隆扩增受阻。 这些有趣的结果支持了以下假设：1）Hmga 1是“年轻”HSC所需的平衡 2）Hmga 1协调活性转录因子的组装， 复合物诱导淋巴发育和再生所需的基因表达，3）Hmga 1丢失 随着年龄的增长，表观基因组被破坏，基因表达改变，HSC功能受损， Hmga 1介导的变化将揭示可能被调节以对抗衰老表型的途径。 目标/方法：为了测试这一点，我们现在提出以下SHINE II计划的单一目标，以刺激 血液学研究的新方向：阐明介导Hmga 1功能的表观遗传机制 在“年轻的”HSC中。A）为了剖析Hmga 1在HSC中的作用，我们将进行体外功能测定， 竞争性BMT与HSC野生型或Hmga 1无效，B）为了鉴定表观遗传改变和发育改变， 在HSC中由Hmga 1控制的通路中，我们将整合ATAC-seq，RNA-seq和ChIP-seq的结果。 影响：我们希望在基因组中识别由Hmga 1介导的特定表观遗传标记和机制途径。 “年轻”HSC。这项工作可能会挑战现有的范式，即HSC中的衰老是不可逆转的， 导致新的临床方法来调节Hmga 1诱导的表观遗传途径， 在老化HSC和可能的其他成体干细胞中的再生功能。

Background: The goal of this proposal is to elucidate epigenetic mechanisms regulated by the high mobility group A1 (Hmga1) chromatin remodeling protein in hematopoietic stem cells (HSC) and to determine how this changes with aging. Hmga1 modulates gene expression by “opening” chromatin and recruiting transcriptional complexes to DNA. While it is clear that alterations in the epigenome and transcriptional networks occur with aging in HSC, the key factors that drive aging phenotypes remain poorly understood. Here, we focus on the Hmga1 chromatin regulator as a key regulator of “youthful” HSC function. Our scientific premise is based on the following preliminary results: 1) Hmga1 expression is enriched in HSC and declines with aging, 2) Mice with global deletion of Hmga1 develop premature aging phenotypes, 3) Hmga1 deficient HSC recapitulate a subset of aging phenotypes, including decreased differentiation to pre- B lymphoid cells in vitro and poor regenerative function in serial bone marrow transplantation (BMT) in vivo. 4) In published work, we discovered that HMGA1: A) maintains a de-differentiated, pluripotent state in human embryonic stem cells by inducing stem cell transcriptional networks, and, B) enhances reprogramming of somatic cells to pluripotent stem cells by the Yamanaka factors. 5) More recently, we uncovered a novel role for HMGA1 as a master regulator of the intestinal stem cell compartment by amplifying Wnt/β-catenin signaling. 6) Published work from our group also demonstrates that de-regulated expression of HMGA1 causes a block in differentiation and clonal expansion in hematopoietic cells. These intriguing results support the hypotheses that: 1) Hmga1 is required by “youthful” HSC for balanced differentiation and regenerative function, 2) Hmga1 orchestrates the assembly of active transcriptional complexes to induce expression of genes required for lymphoid development and regeneration, 3) Hmga1 loss with aging disrupts the epigenome, alters gene expression, and impairs HSC function, 4) Identifying epigenetic changes mediated by Hmga1 will reveal pathways that could be modulated to counter aging phenotypes. Aims/Approach: To test this, we now propose the following Single Aim for the SHINE II Initiative to stimulate new directions in hematology research: To elucidate epigenetic mechanisms which mediate Hmga1 functions in “youthful” HSC. A) To dissect the role of Hmga1 in HSC, we will perform in vitro functional assays and competitive BMT with HSC wildtype or null for Hmga1, B) To identify epigenetic alterations and developmental pathways governed by Hmga1 in HSC, we will integrate results from ATAC-seq, RNA-seq, and ChIP-seq. Impact: We expect to identify specific epigenetic marks and mechanistic pathways mediated by Hmga1 in “youthful” HSC. This work could challenge the existing paradigm that aging in HSC is irreversible and lead to novel clinical approaches to modulate epigenetic pathways induced by Hmga1 to restore regenerative function in aging HSC and possibly other adult stem cells.