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（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，并在氧递送以及产生正常血管发育所必需的剪切力中起着至关重要的作用。尽管它们的功能丰富和不可或缺的功能，但ERYP的发展和成熟度仍然很差。大型，成核的ERYP在蛋黄囊的血岛内出现〜E7.5，并在蛋黄囊和胚胎脉管系统成熟时开始围绕E9.5循环。几天后，确定性红细胞谱系（ERYD）的小细胞开始在胎儿肝脏内分化并进入循环，因此不容易区分这两个谱系。在上一个资金期间，我们开发了转基因小鼠系统，这些系统允许在妊娠期间对ERYP及其核进行标记和跟踪。从这项工作中得出的主要发现是，ERYP通过先前未知的阶段进展，导致其成熟，是在整个妊娠中存在稳定的人群，并且不会逐渐消失，并且它们在胎儿肝的红细胞岛（EBIS）内暂时积累。与ERYP迁移到FL的同时，粘附分子表达的急剧增加以及结合胎儿肝巨噬细胞（FLM）的能力显着提高。 ERYP与FLM结合的能力在发育中受到调节，在胎儿肝内发现的时间窗口中最大，并且部分依赖于VCAM-1。在血液中检测到第一个摘除的ERYP时，在胎儿肝脏中发现了大量的挤出ERYP核。在培养后和天然胎儿肝脏中，可以在FLM中鉴定ERYP核，这表明它们被巨噬细胞清除和降解。摘除后，循环ERYP粘附在巨噬细胞上的能力消失了，它们的数量在FL下降中。我们假设胎儿​​肝脏是原始红细胞成熟的发育生态位，并且在胎儿肝脏的EBIS中发生了ERYP成熟（包括摘除）的末端步骤，并涉及与巨噬细胞的粘合剂相互作用。随着ERYP开始循环，胎儿肝脏正发育，左右在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，即令人困惑的问题是，为什么直到出现后的几天才检测到ERYP的摘除：终末成熟（包括核挤出）发生在胎儿肝脏中，直到中间造成中期才形成。我们在上一个资金期间开发的工具将使我们能够以先前无法解决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儿肝内的ERYP成熟提供了微环境； （2）评估整联蛋白及其受体在原始红细胞成熟中的作用； （3）研究红斑成熟最终阶段的基本事件。公共卫生相关性：祖细胞群体的表征以及对胚胎与成人红细胞发育的共同和区别特征的表征以及与人类ES细胞，HSCS或造血性祖细胞的指导分化的先决条件，用于患者的治疗目的，以及有效地产生纯红色血液群体的纯种细胞。在白血病和骨髓发育异常疾病中，胚胎发育中涉及的红细胞发育涉及的途径可能失调。因此，拟议的研究应具有广泛的生物医学意义。