Erythroid Development in the Mammalian Embryo

哺乳动物胚胎中的红细胞发育

• 批准号: 8010035
• 负责人: Margaret H Baron
• 金额: $ 9.95万
• 依托单位: ICAHN SCHOOL OF MEDICINE AT MOUNT SINAI
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-01-18 至 2010-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8010035
• 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(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重要作用。尽管它们具有丰富的功能和不可或缺的功能，但EryP的发育和成熟仍然没有明确的定义。大的有核EryP从E7.5~E7.5开始出现在卵黄囊的血岛内，并在E9.5左右开始循环，此时卵黄囊和胚胎血管系统之间的连接成熟。几天后，确定的红系血统(EryD)的小细胞开始在胎肝内分化并进入循环，因此这两个血统不容易区分。在之前的资助期间，我们开发了转基因小鼠系统，允许在整个妊娠过程中标记和跟踪EryP及其细胞核。从这项工作中发现的主要发现是，EryP经历了以前未知的阶段，导致它们成熟，它们是一个稳定的群体，在整个妊娠期间存在，不会逐渐消失，并且它们在胎儿肝脏的红细胞岛(EBI)内瞬时积累。伴随着EryP向FL的迁移，黏附分子的表达显著增加，同时结合胎肝巨噬细胞的能力也显著增强。EryP与Flm的结合能力受发育调节，在胎肝内发现它们的时间窗内最大，部分依赖于VCAM-1。当在血液中检测到第一个去核的EryP时，在胎肝内发现了大量挤出的EryP核。在体内，共培养后的成纤维细胞和天然胎肝中均可检测到EryP核，提示它们可被巨噬细胞清除和降解。去核后，循环中的EryP与巨噬细胞的黏附能力丧失，其在FL中的数量减少。我们假设胎肝是原始红细胞成熟的发育场所，EryP成熟的最后步骤，包括去核，发生在胎肝的EBI中，涉及与巨噬细胞的黏附相互作用。随着EryP开始循环，胎儿肝脏正在发育，大约在E9.5左右。因此，我们的观察提出了一个简单的答案，即为什么EryP在出现几天后才被检测到去核这个令人费解的问题：包括核挤出在内的终末成熟发生在胎儿肝脏，直到怀孕中期才形成。我们在前一个资助期开发的工具将使我们能够以以前不可能实现的分辨率来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肝内的EryP成熟提供微环境；(2)评估整合素及其受体在原始红细胞成熟中的作用；以及(3)研究红系成熟末期的分子事件。公共卫生相关性：祖细胞群体的特征和阐明胚胎和成人红系发育的共同和区别特征将是为患者治疗目的定向分化人类ES细胞、造血干细胞或造血祖细胞以及高效生产用于输血的纯红细胞群体的先决条件。在白血病和骨髓增生性疾病中，参与胚胎红系发育的途径可能是失调的。因此，拟议的研究应该具有广泛的生物医学意义。