Erythroid Development in the Mammalian Embryo

哺乳动物胚胎中的红细胞发育

• 批准号: 7853710
• 负责人: Margaret H Baron
• 金额: $ 1.28万
• 依托单位: ICAHN SCHOOL OF MEDICINE AT MOUNT SINAI
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-01 至 2011-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7853710
• 关键词: Adhesions; Adhesives; Adult; Appearance; Binding; Biology; Blood; Blood Circulation; Blood Island; Blood Vessels; Cell Adhesion Molecules; Cell Nucleus; Cell membrane; Cells; Characteristics; Coculture Techniques; Development; Disease; Embryo; Erythroblasts; Erythrocyte Transfusion; Erythrocytes; Erythroid; Erythroid Cells; Erythropoiesis; Event; Fetal Liver; Fibronectins; Funding; Genetic; Hematopoietic; Integrins; Island; Kupffer Cells; Mediating; Membrane Proteins; Modeling; Molecular; Nuclear; Oxygen; Pathway interactions; Patients; Play; Population; Pregnancy; Production; Proteins; Public Health; Resolution; Reticulocytes; Role; Signal Transduction; Solutions; Stable Populations; Staging; Stem cells; System; Therapeutic; Time; Transgenic Mice; Up-Regulation; Vascular Cell Adhesion Molecule-1; Work; Yolk Sac; cell type; human embryonic stem cell; in vivo; insight; knock-down; leukemia; macrophage; migration; progenitor; public health relevance; receptor; response; tool

DESCRIPTION (provided by applicant): EryP are the first differentiated cell type to form in the mammalian embryo and play a vital role in oxygen delivery and in generating shear forces necessary for normal vascular development. Despite their abundance and indispensable functions, the development and maturation of EryP remain poorly defined. Large, nucleated EryP arise within the blood islands of the yolk sac beginning ~E7.5 and begin to circulate around E9.5, when connections between the yolk sac and embryonic vasculature mature. Several days later, small cells of the definitive erythroid lineage (EryD) begin to differentiate within the fetal liver and enter the circulation, so that the two lineages are not easily distinguished. During the previous funding period, we developed transgenic mouse systems that allow the tagging and tracking of EryP and their nuclei throughout gestation. Major findings to emerge from this work were that EryP progress through previously unrecognized stages leading to their maturation, that they are a stable population present throughout gestation and do not gradually disappear, and that they accumulate transiently within the erythroblastic islands (EBIs) of the fetal liver (FL). Concomitant with EryP migration into the FL, a dramatic increase in adhesion molecule expression occurs along with significantly increased ability to bind fetal liver macrophages (FLMs). The ability of EryP to bind to FLMs is developmentally regulated, maximal during the window of time when they are found within the fetal liver, and partly dependent on VCAM-1. Large numbers of extruded EryP nuclei are found within the fetal liver at the time the first enucleated EryP are detected in the blood. EryP nuclei can be identified within FLMs after co- culture and in the native fetal liver, in vivo, suggesting that they are cleared and degraded by macrophages. After enucleation, the ability of circulating EryP to adhere to macrophages is lost and their numbers in the FL decline. We hypothesize that the fetal liver is a developmental niche for the maturation of primitive erythroblasts and that terminal steps in EryP maturation, including enucleation, occur in the EBIs of the fetal liver and involve adhesive interactions with macrophages. The fetal liver is just developing as EryP begin to circulate, around E9.5. Our observations therefore suggest a simple solution to the puzzling question of why enucleation of EryP is not detected until days after their appearance: terminal maturation, including nuclear extrusion, occurs in the fetal liver, which does not form until midgestation. The tools we have developed during the previous funding period will allow us to study the biology of primitive erythropoiesis at a resolution not previously possible. We propose to (1) determine whether macrophages provide a microenvironment for EryP maturation within the fetal liver; (2) evaluate the roles of integrins and their receptors in the maturation of primitive erythroblasts; and (3) investigate molecular events underlying the final stages of erythroid maturation. PUBLIC HEALTH RELEVANCE: Characterization of progenitor cell populations and elucidation of the common as well as the distinguishing features of embryonic versus adult erythroid development will be a prerequisite for the directed differentiation of human ES cells, HSCs or hematopoietic progenitors for therapeutic purposes in patients and for the efficient production of pure populations of red blood cells for transfusion. Pathways involved in erythroid development in the embryo may be dysregulated in leukemias and myelodysplastic disorders. The proposed studies should therefore be of broad biomedical significance.

描述（由申请人提供）：EryP 是在哺乳动物胚胎中形成的第一种分化细胞类型，在氧气输送和产生正常血管发育所需的剪切力方面发挥着至关重要的作用。尽管其功能丰富且不可或缺，但 EryP 的发展和成熟仍不明确。当卵黄囊和胚胎脉管系统之间的连接成熟时，大的有核 EryP 从 ~E7.5 开始出现在卵黄囊的血岛内，并开始在 E9.5 周围循环。几天后，终型红细胞谱系（EryD）的小细胞开始在胎儿肝脏内分化并进入循环系统，因此这两个谱系不容易区分。在之前的资助期间，我们开发了转基因小鼠系统，可以在整个妊娠期间标记和跟踪 EryP 及其细胞核。这项工作的主要发现是，EryP 通过以前未被识别的阶段进展直至成熟，它们是整个妊娠过程中存在的稳定群体，不会逐渐消失，并且它们在胎儿肝脏 (FL) 的成红细胞岛 (EBI) 内短暂积累。随着 EryP 迁移到 FL，粘附分子表达显着增加，同时结合胎儿肝脏巨噬细胞 (FLM) 的能力也显着增加。 EryP 与 FLM 结合的能力受到发育调节，在胎儿肝脏内发现 FLM 的时间窗口内达到最大，并且部分依赖于 VCAM-1。当血液中检测到第一个去核的 EryP 时，在胎儿肝脏内发现大量挤出的 EryP 核。 EryP 核可以在共培养后的 FLM 内和在体内的天然胎儿肝脏中被识别，这表明它们被巨噬细胞清除和降解。去核后，循环 EryP 粘附巨噬细胞的能力丧失，巨噬细胞在 FL 中的数量下降。我们假设胎儿​​肝脏是原始成红细胞成熟的发育生态位，并且 EryP 成熟的最终步骤（包括去核）发生在胎儿肝脏的 EBI 中，并涉及与巨噬细胞的粘附相互作用。当 EryP 开始循环时，胎儿肝脏刚刚发育，大约在 E9.5 左右。因此，我们的观察结果提出了一个简单的解决方案，可以解决为什么 EryP 去核直到出现几天后才被检测到的令人困惑的问题：最终成熟，包括核挤出，发生在胎儿肝脏中，胎儿肝脏直到妊娠中期才形成。我们在上一个资助期间开发的工具将使我们能够以以前不可能的分辨率研究原始红细胞生成的生物学。我们建议（1）确定巨噬细胞是否为胎儿肝脏内的 EryP 成熟提供微环境； (2)评价整合素及其受体在原始红细胞成熟中的作用； (3) 研究红细胞成熟最后阶段的分子事件。公共卫生相关性：祖细胞群的表征以及胚胎与成人红细胞发育的共同特征和区别特征的阐明将是定向分化人类 ES 细胞、HSC 或造血祖细胞用于患者治疗目的以及有效生产用于输血的纯红细胞群的先决条件。在白血病和骨髓增生异常性疾病中，参与胚胎红细胞发育的途径可能失调。因此，拟议的研究应该具有广泛的生物医学意义。