Epigenetic dysregulation of transcription factor NF-E2 expression in thepathophysiology of myeloproliferative neoplasms

骨髓增生性肿瘤（MPN）构成了一组恶性血液系统疾病，易导致急性白血病的发展。尽管最近JAK2V617F突变的发现使我们对MPN病因的理解取得了进展，但一个核心问题仍未解决：JAK2V617F促进MPN发展的分子机制尚未阐明。鉴于最近临床试验中观察到的JAK2抑制剂的有限疗效，这一缺陷显得尤为重要。最近，一种新的、不依赖stat的JAK2活性的表观遗传途径被描述，该途径涉及JAK2的组蛋白磷酸化和随后的染色质结合蛋白的调节。我们已经证明转录因子NF-E2在MPN患者中过度表达，并且在小鼠模型中NF-E2水平升高导致MPN表型，包括自发转化为急性白血病。然而，导致NF-E2过表达的分子机制尚未明确。在初步数据中，我们已经证明NF-E2在健康对照中是表观遗传沉默的，而这种沉默在MPN患者中不存在。因此，本项目的目的是研究影响MPN患者表观遗传NF-E2沉默失调的分子机制，并描述JAK2V617F突变对NF-E2表达的影响。假设1：在MPN患者中，地西他滨介导的NF-E2表达下降和生理性成熟诱导的NF-E2表达下降都受到上游信号通路的调节和组蛋白修饰的介导。假设2:NF-E2在MPN患者中的过表达是通过JAK2/phospho-H3Y41/HP-1alpha途径受到h3y41磷酸化的影响。假设3:NF-E2在MPN患者中的过表达受组蛋白甲基化酶或去甲基化酶活性改变的影响，导致NF-E2启动子中组蛋白甲基化异常。阐明导致NF-E2过表达的分子机制将有助于更好地了解MPN疾病的病因。由于靶向转录因子的治疗是非常具有挑战性的，因此被确定为NF-E2过度表达的途径可能更适合作为药物靶点。

Myeloproliferative Neoplasms (MPN) constitute a group of malignant, hematological disorders that predispose to the development of acute leukemia. Despite recent advances in our understanding of MPN etiology, brought on by the discovery of the JAK2V617F mutation, a central problem remains unsolved: the molecular mechanisms by which JAK2V617F contributes to the development of MPNs have not been elucidated. This shortcoming appears especially relevant in light of the limited efficacy of JAK2 inhibitors observed in recent clinical trials. Recently, a novel, STAT-independent, epigenetic pathway of JAK2 activity was described, that involves histone phosphorylation by JAK2 and subsequent modulation of chromatin binding proteins.We have demonstrated that the transcription factor NF-E2 is overexpressed in MPN patients and that elevated NF-E2 levels cause an MPN phenotype in a mouse model including spontaneous transformation to acute leukemia. However, the molecular mechanisms causing NF-E2 overexpression have not been delineated. In preliminary data, we have demonstrated that NF-E2 is epigenetically silenced in healthy controls and that this silencing is absent in MPN patients. The aims of this project are therefore to investigate the molecular mechanisms effecting dysregulated epigenetic NF-E2 silencing in MPN patients and to delineate the effects of the JAK2V617F mutation on NF-E2 expression. The following hypotheses will be investigated:Hypothesis 1: Both the Decitabine-mediated and the physiological, maturation induced decrease in NF-E2 expression, which is perturbed in MPN patients, are regulated by upstream signaling pathways and mediated by histone modification. Hypothesis 2: NF-E2 overexpression in MPN patients is effected by H3Y41-phosphorylation via the novel JAK2/phospho-H3Y41/HP-1alpha pathway.Hypothesis 3: NF-E2 overexpression in MPN patients is effected by altered activity of histone methylases or demethylases causing aberrant histone methylation in the NF-E2 promoter.Elucidating the molecular mechanisms causing NF-E2 overexpression will lead to a better understanding of MPN disease etiology. Since targeting a transcription factor therapeutically is very challenging, the pathways identified as causal for NF-E2 overexpression may better lend themselves as drug targets.