ARHGEF12基因在稳态与应激性红系造血中的调控作用及机制研究

Chemotherapy for hematologic malignancies such as acute lymphoblastic leukemia (ALL) often causes anemia. The degree of chemotherapy-related anemia is directly related to the success rate of chemotherapy. Genome association study revealed that some polymorphisms in ARHGEF12 were significantly related to the degree of chemotherapy induced anemia in children with acute lymphoblastic leukemia.ARHGEF12 is a RhoA-specific guanine-exchange factor and highly expressed in erythroid cells. A role of ARHGEF12 and its homologs in erythroid differentiation was confirmed in human K562 cells and zebrafish embryo. The p38 kinase pathway was affected by the ARHGEF12-RhoA signaling in K562 cells, and consistently, the arhgef12-rhoA-p38 pathway was also shown to be important for erythroid differentiation in zebrafish as active rhoA or p38 readily rescued the impaired erythropoiesis caused by arhgef12 knocking down. This project will study the regulation and mechanism of ARHGEF12 on erythropoiesis, especially stress erythropoiesis, and explore the chemotherapy-induced anemia-inducing drugs associated with down-regulation of ARHGEF12 by a conditional knockout mouse model. Small molecule compounds that target related pathways will be used to ameliorate chemotherapy-induced anemia. The findings will be useful to understand the regulation of ARHGEF12-RhoA on erythropoiesis more comprehensively, especially chemotherapy related stress erythropoiesis, and provides a new way to prevent and treat chemotherapy induced anemia and thereby reducing red blood cell transfusion.

化疗是白血病的主要治疗手段之一，贫血是化疗引起的一个重要毒副作用，化疗相关的贫血程度直接与化疗的成功率相关。我们前期基于基因组学研究发现ARHGEF12基因多态性显著影响儿童急性淋巴细胞白血病化疗后的贫血程度。ARHGEF12是RhoA特异性鸟苷交换因子，在红系特异性高表达。我们进一步在K562细胞株及斑马鱼胚胎中证实ARHGEF12通过RhoA-P38影响红系分化。本项目将通过可调控的条件性基因敲除小鼠模型研究ARHGEF12对红系造血尤其是化疗后应激性红系造血的调控作用及其机制，探索ARHGEF12基因表达不足时诱发贫血的化疗药物，并利用小分子化合物等调节相关通路来减轻贫血程度。本研究将有助于更加全面地了解ARHGEF12-RhoA对红系造血尤其是应激性红系造血的调控作用，为肿瘤化疗后贫血的防治、减少输血提供可能的新途径。

化疗是急性淋巴细胞白血病主要的治疗手段，但化疗药物相关的毒副反应愈发引起关注，最常见后果之一是严重且潜在致命的贫血。即使接受同样程度的化疗，患儿间贫血程度差异很大，影响血制品输注需求及输血相关不良反应发生率。通过全外显子测序及生物信息学分析，发现ARHGEF12基因多态性与贫血程度显著相关，参与调节化疗后贫血的应激性红系造血，并通过斑马鱼模型证实它也调控正常红系造血发育。新发现调控化疗后造血恢复的信号通路——ARHGEF12/Rhoa/P38，提出预测化疗相关贫血程度的生物标记物——rs10892563。利用可诱导敲除的条件性敲除小鼠模型揭示了ARHGEF12 对稳态红系造血以及化疗后应激性红系造血的调控作用，Arhgef12敲除导致正细胞正色素性贫血，骨髓红系发育受阻在红系前体细胞及早幼红细胞向下游更成熟红细胞分化的阶段，而不影响其余各系分化。利用阿糖胞苷、巯嘌呤等临床常用化疗药物模拟化疗诱导贫血，Arhgef12表达不足时贫血程度重且恢复较慢，正开展罗沙司他等药物减轻贫血的试验探索，期望通过干预相关通路减轻贫血程度，减轻输血依赖。