Erythropoietin receptor signaling in stress erythropoiesis and erythrocytosis

项目总结 促红细胞生成素(EPO)及其受体EPOR是红细胞生成的主要调节因子。 正常的EPO水平支持基础红细胞生成。在贫血、失血或缺氧时，促红细胞生成素 水平上升，启动信号通路扩大红系祖细胞，增加红色 红细胞生成应激反应过程中的细胞产生。在出版的作品中，我们展示了 在骨髓增生性疾病中发现的结构性活性JAK2突变体JAK2(V617F) 肿瘤，需要与EPOR结合来传递致癌信号 红系祖细胞驱动红细胞增多症。而EPOR信号在分化程度更高的 红系前体已被广泛研究，早期祖细胞中的EPOR信号， 其中控制应激性红细胞生成和红细胞增多症的机制尚未阐明。 在初步研究中，我们发现JAK2(V617F)致癌信号需要 远端EPOR胞质结构域。因为这个远端的EPOR结构域对于应激是必不可少的 JAK2(V617F)可劫持EPOR- 驱动红细胞增多症的依赖应激红细胞生成途径。使用新流程 细胞学策略，我们发现了一个以前未被识别的早期群体- 形成红系祖细胞(CFU-E)，我们称之为应激性CFU-E或sCFU-E，称为 JAK2(V617F)驱动信号和应激性红细胞生成素的特异性靶点 回应。 阐明支持sCFU-E扩张的EPOR信号可能揭示新的治疗方法 可以针对红血球的途径，同时避免正常的红血球生成。中环 这项提案的目标是表征依赖EPOR的机制，这些机制推动 SCFU-E在应激性红细胞生成和JAK2(V617F)驱动的红细胞增多症中的扩张。 目的1确定sCFU-E扩展中的机制和EPOR信号。目标2 利用我们新的RNA-SEQ数据来研究EPOR下游的新型调节剂 应激性红细胞生成、小鼠红细胞增多症和人真性红细胞增多症。一起， 这些结果将阐明控制应激性红细胞生成和 病理性红细胞增多症，并可能导致新的治疗干预措施。

PROJECT SUMMARY Erythropoietin (Epo) and its receptor EpoR are primary regulators of erythropoiesis. Normal Epo levels support basal erythropoiesis. In anemia, blood loss, or hypoxia, Epo levels rise, initiating signaling pathways to expand erythroid progenitors, increasing red cell production during the erythropoietic stress response. In published work, we showed that the constitutively active JAK2 mutant JAK2(V617F), found in myeloproliferative neoplasms, needs to associate with the EpoR to transmit oncogenic signaling in erythroid progenitors to drive erythrocytosis. While EpoR signaling in more differentiated erythroid precursors has been extensively studied, EpoR signaling in early progenitors, which controls stress erythropoiesis and erythrocytosis, has not been elucidated. In preliminary studies, we show that JAK2(V617F) oncogenic signaling requires the distal EpoR cytoplasmic domain. Because this distal EpoR domain is essential for stress erythropoiesis but dispensable for basal erythropoiesis, JAK2(V617F) may hijack EpoR- dependent stress erythropoiesis pathways to drive erythrocytosis. Using a new flow cytometry strategy, we identified a previously unrecognized population of early colony- forming erythroid progenitors (CFU-E), which we named stress CFU-E or sCFU-E, as a specific target of both the JAK2(V617F)-driven signals and the stress erythropoietic response. Elucidating EpoR signaling that supports sCFU-E expansion may reveal new therapeutic avenues that can target erythrocytosis while sparing normal erythropoiesis. The central goal of this proposal is to characterize the EpoR-dependent mechanisms that drive sCFU-E expansion in stress erythropoiesis and in JAK2(V617F)-driven erythrocytosis. Aim 1 determines mechanisms and EpoR signaling in sCFU-E expansion. Aim 2 leverages our new RNA-seq data to examine novel regulators downstream of EpoR in stress erythropoiesis, murine erythrocytosis and human polycythemia vera. Together, these results will elucidate mechanisms controlling stress erythropoiesis and pathological erythrocytosis, and may lead to novel therapeutic interventions.