Role of embryonic multipotent progenitors in hematopoietic ageing

胚胎多能祖细胞在造血衰老中的作用

• 批准号: 10650441
• 负责人: Michael Ian Quach
• 金额: $ 1.57万
• 依托单位: BOSTON CHILDREN'S HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-05-31 至 2023-07-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10650441
• 关键词: ATAC-seq; Ablation; Acceleration; Adult; Age; Aging; Biological Assay; Blood; Blood Cells; Bone Marrow; Cardiovascular Diseases; Cardiovascular system; Cause of Death; Cell Compartmentation; Cells; Chromatin; Chronic; Data; Defect; Deterioration; Development; Disease; Drops; Elderly; Embryo; Embryo Loss; Embryonic Development; Epigenetic Process; Equilibrium; Etiology; Exclusion; Fetal Development; Generations; Genes; Genetic; Genetic Transcription; Goals; Growth; Health; Healthcare Systems; Hematology; Hematopoiesis; Hematopoietic; Hematopoietic System; Hematopoietic stem cells; Human; Immune; Immunity; Individual; Infection; Inflammaging; Inflammation; Label; Life; Longevity; Lymphocyte; Lymphoid; Lymphoid Cell; Lymphopoiesis; Modeling; Molecular Analysis; Multipotent Stem Cells; Mus; Myelogenous; Myeloproliferative disease; Older Population; Phenotype; Population; Predisposition; Production; Risk; Role; Source; System; Techniques; Testing; Thrombosis; Transcript; Translating; Transplantation; Up-Regulation; Vaccination; Work; adaptive immune response; adaptive immunity; age related; aged; blastomere structure; differential expression; embryo cell; hematopoietic stem cell expansion; hemogenic endothelium; high risk; infection rate; infection risk; insight; leukemia; novel; overexpression; progenitor; screening; self-renewal; stem cell population; stem cells; thrombotic; tool; transcriptome sequencing; transcriptomics; treatment strategy; young adult

Project Summary/Abstract In humans, aging is associated with chronic inflammation and a decline in adaptive immunity, leading to higher rates of infection and cardiovascular disease, two of the leading causes of death in adults over 65. These hematologic defects are due in part to deficiencies in aged hematopoiesis, which is biased toward myeloid lineages. Many studies on aged hematopoiesis rely on transplantation assays or isolation of specific hematopoietic stem cell (HSC) populations for molecular analysis. While these studies highlight important features of aged HSCs, their approaches focus on long-term (LT) HSCs, a small subset of hematopoietic cells, often to the exclusion of other progenitor populations. Recent studies employ inducible genetic tags to track unperturbed native hematopoiesis. Many of these studies suggest that a large number of progenitor clones, rather than LT-HSCs, drive the bulk of adult hematopoiesis. However, the precise origin of these progenitors remains unclear. Our preliminary work using the transposon tagging technique developed in our lab to tag cells throughout embryonic development indicates that a large portion of adult blood bears tags associated with MPPs, without a corresponding tag in the HSC population. Thus, these MPPs are not clonally related to HSCs, but rather were tagged as a previously unappreciated population of embryonic MPPs (eMPPs). Mature blood contributions from eMPPs were detected when tagging was induced as early as E9.5. However, it remains unclear at which stage of development eMPPs first emerge, and whether earlier hematopoietic cells, such as hemogenic endothelium, are primed to generate eMPPs. By E11.5, increased expression of several lymphoid- associated transcripts appears to separate eMPPs from HSCs. We hypothesize that unique transcriptomic and epigenetic features can predict eMPP divergence during development. To test this hypothesis, we will perform single-cell ATAC-seq and RNA-seq on hematopoietic cells from embryos at several developmental stages. We anticipate that tracking transcriptomic and epigenetic state in embryonic hematopoietic populations will allow us to identify the emergence of eMPPs and, potentially, populations which are primed to generate them. Preliminary data also indicate that eMPPs’ large contributions to hematopoiesis decline with age, and that eMPPs generate the majority of mature lymphoid cells throughout all adult life. We hypothesize that eMPPs are vital to lymphoid production, and their age-dependent decline underlies myeloid bias in aged hematopoiesis. To test this hypothesis, we will genetically ablate eMPPs during fetal development and detect the effects of the loss of eMPPs on the lineage balance of mature blood and expansion of HSCs in the bone marrow. Conversely, we will attempt to rescue the aged phenotype via overexpression of Hoxb4 and Meis1, two genes associated with self- renewal in HSCs, in MPPs. Our findings will not only elucidate the origin eMPPs in development, but also have the potential to challenge our current understanding of aging in the hematopoietic system, providing insight into the etiologies of many age-related hematologic defects.

项目概要/摘要 在人类中，衰老与慢性炎症和适应性免疫力下降有关，从而导致 感染率和心血管疾病率较高，这是 65 岁以上成年人死亡的两个主要原因。 血液学缺陷部分是由于老年造血功能缺陷所致，偏向于骨髓细胞 血统。许多关于老年造血的研究依赖于移植测定或特定的分离 用于分子分析的造血干细胞 (HSC) 群体。虽然这些研究强调了重要的 老化 HSC 的特征，他们的方法侧重于长期 (LT) HSC，这是造血细胞的一小部分， 往往会排斥其他祖先群体。最近的研究利用诱导基因标签来追踪 不受干扰的天然造血功能。许多这些研究表明大量的祖细胞克隆， 而非 LT-HSC 驱动大部分成人造血作用。然而，这些祖先的确切起源 仍不清楚。我们的初步工作是使用我们实验室开发的转座子标记技术来标记细胞 整个胚胎发育过程表明，大部分成人血液带有与 MPP 相关的标签， HSC 群体中没有相应的标签。因此，这些 MPP 与 HSC 没有克隆相关性，但是 相反，它们被标记为以前未被重视的胚胎 MPP（eMPP）群体。成熟的血液 早在 E9.5 诱导标记时就检测到了 eMPP 的贡献。然而，它仍然 目前尚不清楚 eMPP 在发育的哪个阶段首次出现，以及早期造血细胞是否存在，例如 造血内皮细胞已准备好生成 eMPP。到 E11.5，几种淋巴样的表达增加 相关转录本似乎将 eMPP 与 HSC 分开。我们假设独特的转录组和 表观遗传特征可以预测发育过程中的 eMPP 分歧。为了检验这个假设，我们将执行 对多个发育阶段胚胎的造血细胞进行单细胞 ATAC-seq 和 RNA-seq。我们 预计追踪胚胎造血群体的转录组和表观遗传状态将使我们能够 以确定 eMPP 的出现以及可能产生它们的人群。初步的 数据还表明，eMPP 对造血的巨大贡献随着年龄的增长而下降，并且 eMPP 产生 整个成年期的大多数成熟淋巴细胞。我们假设 eMPP 对淋巴至关重要 其产量及其与年龄相关的下降是老年造血中骨髓偏向的基础。为了测试这个 假设，我们将在胎儿发育过程中从基因上消除 eMPP，并检测失去 eMPP 的影响 eMPP 对成熟血液谱系平衡和骨髓中 HSC 扩张的影响。相反，我们将 尝试通过 Hoxb4 和 Meis1 的过度表达来挽救衰老表型，这两个基因与自我相关 HSC 和 MPP 的更新。我们的研究结果不仅将阐明发育中的 eMPP 的起源，而且还 有可能挑战我们目前对造血系统衰老的理解，提供深入了解 许多与年龄相关的血液学缺陷的病因。