Regulation of the lymphoid cell fate by Hoxa9

Hoxa9 对淋巴细胞命运的调节

基本信息

批准号：
10546476
负责人：
Kay Lynn Medina
金额：
$ 31.8万
依托单位：
MAYO CLINIC ROCHESTER
依托单位国家：
美国
项目类别：
财政年份：
2022
资助国家：
美国
起止时间：
2022-01-15 至 2024-11-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10546476
关键词：
Age Aging Attention B-Lymphocytes Blood Cells Bone Marrow CDKN2A gene Cell Compartmentation Cell Lineage Cells Cellularity Common Lymphoid Progenitor Cyclin-Dependent Kinase Inhibitor Data Defect Development Elderly Exhibits Frequencies Genes Goals HOXA9 protein Hematology Hematopoiesis Hematopoietic Hematopoietic Stem Cell subsets Hematopoietic stem cells Homeobox Immune System Diseases Immunocompetence Impairment In Vitro Infection Knockout Mice Knowledge Life Lymphocyte Lymphoid Lymphoid Cell Lymphopoiesis Maintenance Marrow Messenger RNA Modeling Molecular Mus Myelogenous Output Proliferating Publications Radiation Chimera Regulation Rejuvenation Role SLAM protein T-Lymphocyte Thymus Gland Time Transcript Transplantation Tumor Suppressor Genes aged cytokine experimental study genomic locus humoral immunity deficiency immune function novel novel therapeutics overexpression p19ARF progenitor promoter response senescence stem cell biology stem cells transcription factor tumorigenesis vaccine response virtual young adult

项目摘要

PROJECT SUMMARY Steady-state hematopoiesis in bone marrow is critical for maintenance of blood cell genesis and immune competence throughout life. Concomitant with aging, the bone marrow hematopoietic stem cell (HSC) compartment undergoes cell intrinsic and extrinsic changes that biases hematopoietic output toward the myeloid lineage. The bias in HSC-subset predominance and change in hematopoietic output contributes to immune dysfunction in the elderly including an increased propensity to infection and lessened vaccine responses. Thus, studies focused on understanding essential regulators that support a non-biased, balanced HSC pool that supports lymphoid differentiation capability has the potential to provide novel therapeutic avenues to rejuvenate HSC developmental trajectories to restore immune function in the aged. The homeobox transcription factor Hoxa9 is expressed in primitive HSCs and is inactivated upon lineage commitment. Mice with germline deletion of hoxa9 are viable but display multilineage deficiencies that are transplantable, confirming a cell intrinsic defect. Competitive transplantation experiments revealed impaired long-term repopulating ability and in vitro studies showed poor proliferative responses to early-acting cytokines. In bone marrow, hoxa9-/- mice exhibit reduced cellularity, impaired lymphoid priming, reductions in lympho-myeloid progenitors, common lymphoid progenitors, and B cell precursors. Hoxa9-/- mice also have smaller thymi, and reductions in early thymic progenitors. Interestingly, flow cytometric analysis of the long-term repopulating stem cell compartment (LT-HSC) in young adult hoxa9-/- mice revealed increased frequencies of LT-HSCs expressing high levels of the CD150, which is functionally associated with myeloid skewing. This is contrasted by significant decreases in frequencies of CD150lo LT-HSC in hoxa9-/- marrow, which have balanced lympho- myeloid potential. Increased numbers of myeloid-biased HSCs along with diminished lymphopoiesis is reminiscent of aging. A Hoxa9 target gene implicated in age-associated alterations in lymphopoiesis and B cell genesis in the marrow is p16ink4a. The cyclin dependent kinase inhibitor p16ink4a is virtually undetectable in HSC and B cell precursors from young mice but increases in both subsets with age. Realtime PCR of Lin- Sca1+ hematopoietic progenitors from young hoxa9-/- mice revealed increased mRNA transcripts for p16ink4a. To determine if over expression of p16ink4a was the molecular basis of the lymphoid/B cell deficiency in hoxa9-/- mice, we generated hoxa9-/-p16ink4a-/- mice. Importantly, deletion of p16ink4a restored bone marrow and thymus cellularity and rescued the deficiencies in lymphoid, B and T cell precursors in hoxa9-/- mice. These novel experimental findings support the hypothesis that Hoxa9 suppression of p16ink4a is critical for lymphopoiesis. At present, there is a paucity of information regarding the role of Hoxa9 in regulation of lympho-hematopoiesis. The studies detailed in this proposal are aimed at filling this gap in the knowledge.

项目概要骨髓中的稳态造血对于维持血细胞发生和免疫至关重要终生的能力。随着衰老，骨髓造血干细胞（HSC）隔室经历细胞内在和外在的变化，使造血输出偏向骨髓谱系。 HSC 子集优势的偏差和造血输出的变化导致老年人的免疫功能障碍，包括感染倾向增加和疫苗接种减少回应。因此，研究的重点是了解支持无偏见、平衡的基本监管机构支持淋巴分化能力的 HSC 池有可能提供新的治疗方法恢复 HSC 发育轨迹以恢复老年人免疫功能的途径。同源框转录因子 Hoxa9 在原始 HSC 中表达，并在谱系定型后失活。小鼠 hoxa9 种系缺失是可行的，但表现出可移植的多谱系缺陷，确认细胞内在缺陷。竞争性移植实验显示长期受损增殖能力和体外研究显示对早期作用细胞因子的增殖反应较差。在骨头里骨髓，hoxa9-/- 小鼠表现出细胞结构减少、淋巴启动受损、淋巴髓样减少祖细胞、共同淋巴祖细胞和 B 细胞前体细胞。 Hoxa9-/- 小鼠的胸腺也较小，并且早期胸腺祖细胞减少。有趣的是，长期再生干的流式细胞术分析年轻成年 hoxa9-/- 小鼠的细胞区室 (LT-HSC) 显示 LT-HSC 频率增加表达高水平的 CD150，其功能与骨髓偏向相关。这是对比的通过 hoxa9-/- 骨髓中 CD150lo LT-HSC 的频率显着降低，这具有平衡的淋巴- 骨髓潜能。偏向髓系的 HSC 数量增加，同时淋巴细胞生成减少让人想起衰老。 Hoxa9 靶基因与年龄相关的淋巴细胞生成和 B 细胞改变有关骨髓中的起源是p16ink4a。细胞周期蛋白依赖性激酶抑制剂 p16ink4a 在 HSC 和 B 细胞前体来自年轻小鼠，但随着年龄的增长，这两个亚群都会增加。 Lin- 的实时 PCR 来自年轻 hoxa9-/- 小鼠的 Sca1+ 造血祖细胞显示 mRNA 转录物增加 p16ink4a。确定 p16ink4a 的过度表达是否是淋巴样/B 细胞的分子基础 hoxa9-/- 小鼠缺乏缺陷，我们生成了 hoxa9-/-p16ink4a-/- 小鼠。重要的是，p16ink4a 的删除恢复了骨髓和胸腺细胞结构，并挽救了淋巴、B 和 T 细胞前体细胞的缺陷 hoxa9-/- 小鼠。这些新的实验结果支持 Hoxa9 抑制 p16ink4a 的假设对于淋巴细胞生成至关重要。目前，关于 Hoxa9 在细胞中的作用的信息还很缺乏。淋巴造血的调节。本提案中详述的研究旨在填补这一空白知识。