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。尽管它们的丰富和不可或缺的功能，EryP的发育和成熟仍然不清楚。大的、有核的EryP从约E7.5开始出现在卵黄囊的血岛内，并且当卵黄囊和胚胎脉管系统之间的连接成熟时，开始在E9.5左右循环。几天后，定形红细胞谱系（EryD）的小细胞开始在胎肝内分化并进入循环，使得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，允许在整个妊娠期间标记和跟踪EryP及其细胞核。从这项工作中出现的主要发现是，EryP的进展，通过以前未认识到的阶段，导致他们的成熟，他们是一个稳定的人口存在于整个妊娠期，并没有逐渐消失，他们暂时积累内的成红细胞岛（EBI）的胎儿肝脏（FL）。伴随EryP迁移到FL中，粘附分子表达的急剧增加沿着发生，同时结合胎肝巨噬细胞（FLM）的能力显著增加。EryP与FLM结合的能力是发育调节的，在胎肝内发现FLM的时间窗期间最大，并且部分依赖于VCAM-1。当在血液中检测到第一个去核的EryP时，在胎肝内发现大量挤出的EryP核。EryP核可以在共培养后的FLM内和在体内天然胎肝中鉴定，表明它们被巨噬细胞清除和降解。去核后，循环EryP粘附于巨噬细胞的能力丧失，并且它们在FL中的数量下降。我们假设胎肝是原始成红细胞成熟的发育生态位，EryP成熟的终末步骤，包括去核，发生在胎肝的EBI中，并涉及与巨噬细胞的粘附相互作用。E9.5左右，EryP开始循环时，胎儿肝脏刚刚发育。因此，我们的观察结果提出了一个简单的解决方案，令人费解的问题，为什么去核EryP是没有检测到，直到几天后，他们的外观：终端成熟，包括核挤出，发生在胎儿肝脏，这不形成，直到妊娠中期。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）确定巨噬细胞是否提供了一个微环境的EryP成熟的胎儿肝脏内;（2）评估的作用，整合素及其受体的成熟的原始成红细胞;（3）调查的分子事件的红细胞成熟的最后阶段。公共卫生关系：祖细胞群的表征和阐明胚胎与成人红细胞发育的共同特征以及区别特征将是用于患者治疗目的的人ES细胞、HSC或造血祖细胞的定向分化以及用于输血的纯红细胞群的有效生产的先决条件。在白血病和骨髓增生异常疾病中，胚胎中涉及红细胞发育的途径可能失调。因此，拟议的研究应具有广泛的生物医学意义。