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

骨髓增生性肿瘤（MPN）是一组易发生急性白血病的恶性血液病。尽管最近我们对MPN病因学的理解取得了进展，但JAK 2 V617 F突变的发现仍然没有解决一个核心问题：JAK 2 V617 F促进MPN发展的分子机制尚未阐明。鉴于在最近的临床试验中观察到的JAK 2抑制剂的有限功效，该缺点似乎特别相关。最近，一种新的，STAT-独立的，JAK 2活性的表观遗传途径被描述，这涉及组蛋白磷酸化JAK 2和随后的染色质结合蛋白的调制，我们已经证明，转录因子NF-E2在MPN患者中过表达，NF-E2水平升高导致MPN表型在小鼠模型中，包括自发转化为急性白血病。然而，引起NF-E2过表达的分子机制尚未阐明。在初步数据中，我们已经证明，NF-E2在健康对照中表观遗传沉默，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患者中表观遗传学NF-E2沉默失调的分子机制，并描述JAK 2 V617 F突变对NF-E2表达的影响。将研究以下假设：假设1：地西他滨介导的和生理性成熟诱导的NF-E2表达降低，其在MPN患者中受到干扰，受上游信号传导途径调节并由组蛋白修饰介导。假设二：MPN患者中NF-E2的过度表达是通过JAK 2/磷酸化H3 Y 41/HP-1 α通路的H3 Y 41磷酸化而实现的假设3：MPN患者中NF-E2的过度表达是通过组蛋白甲基化酶或去甲基化酶的活性改变而实现的，从而导致NF-E2启动子的异常甲基化，阐明NF-E2过度表达的分子机制将有助于更好地理解MPN疾病的病因。由于靶向转录因子治疗是非常具有挑战性的，被鉴定为NF-E2过表达的原因的途径可能更好地适合作为药物靶点。

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.