Mechanistic roles of BCL11A in globin switching and fetal hemoglobin silencing

描述(由申请人提供)：人类从胎儿(3)到成人(2)的发育转变代表了发育基因调控的一个临床重要例子。转录因子BCL11A是新近发现的3-珠蛋白沉默和血红蛋白转换的关键调节因子。BCL11A编码锌指抑制蛋白，与人类2-珠蛋白簇内的序列结合，并通过调节染色体环的形成来重新配置该基因座。BCL11A控制原始人类红系前体和携带人类2-珠蛋白簇转基因小鼠的3-珠蛋白基因的发育沉默。因此，对BCL11A及其协同因子的重点研究应该可以对相关机制进行剖析，并可能揭示2-血红蛋白紊乱患者胎儿血红蛋白(HBF)重新激活的其他靶点。在这个项目中，徐博士将检验BCL11A通过与转录共抑制物复合体合作并调节染色体的远程相互作用来沉默HBF表达的假说。本研究的目的是：1.通过综合基因组分析确定BCL11A的靶基因；2.深入剖析BCL11A调控3-珠蛋白转录和血红蛋白转换的分子机制；3.探讨LSD1/corest复合体在BCL11A介导的3-珠蛋白表达沉默中的作用。徐健博士是波士顿儿童医院霍华德·休斯医学研究所的博士后研究员，他提出的5年指导职业生涯计划将在波士顿儿童医院血液/肿瘤科的Stuart Orkin博士的实验室进行。徐博士的背景是分子和发育生物学，他的长期职业目标是成为一名独立的研究员，在血细胞发育和疾病的基本机制方面拥有专业知识。在转录调控、造血和干细胞生物学领域公认的领导者奥尔金博士的指导下，徐博士开发了一个研究和培训平台，使他能够获得在指导和独立环境下进行生产所必需的实验技能和知识。为了实现这一目标，徐博士将利用奥金实验室的专业知识和资源，在相关研究领域获得更多技能和培训，并与专家团队建立合作。鉴于波士顿儿童医院在丰富和协作的环境中培训研究科学家的杰出记录，该计划在波士顿儿童医院的血液科/肿瘤科进行是理想的。 与公共卫生相关：镰状细胞性贫血和2-地中海贫血等2-Hb疾病是一个主要的公共卫生问题。胎儿血红蛋白(HBF)水平升高与这些疾病的发病率和死亡率降低相关。为了治疗的目的，人们对开发诱导HBF表达的方法非常感兴趣。BCL11A作为HBF表达的关键抑制因子的发现和验证为珠蛋白基因调控领域注入了新的活力。在这项提议中，我试图阐明BCL11A控制HBF沉默和血红蛋白切换的分子机制，作为靶向重新激活HBF的一种手段。我将系统地探讨BCL11A协同因子在HbF表达的发育沉默中的作用。这些研究结果将促进我们对BCL11A在HBF沉默中的作用的理解，并为主要血红蛋白疾病患者的靶向治疗提供新的线索。

DESCRIPTION (provided by applicant): The developmental switch from human fetal (3) to adult (2) hemoglobin represents a clinically important example of developmental gene regulation. The transcription factor BCL11A is a newly identified critical regulator of 3-globin silencing and hemoglobin switching. BCL11A, which encodes a zinc-finger repressor protein, binds to sequences within the human 2-globin cluster and reconfigures the locus by modulating chromosomal loop formation. BCL11A controls the developmental silencing of 3-globin genes in primary human erythroid precursors and in mice carrying a human 2-globin cluster transgene. Therefore, focused study of BCL11A and its cooperating factors should allow dissection of the mechanisms involved and may reveal additional targets for reactivation of fetal hemoglobin (HbF) in patients with 2-hemoglobin disorders. In this project, Dr. Xu will test the hypothesis that BCL11A silences HbF expression through cooperating with transcriptional co-repressor complexes and modulating long-range chromosomal interactions. Specifically, this proposal will aim to: 1. Determine target genes of BCL11A by integrative genomic analysis, 2. Dissect in greater depth the molecular mechanisms by which BCL11A modulates 3-globin transcription and hemoglobin switching and 3. Explore the contribution of LSD1/CoREST complexes to BCL11A-mediated silencing of 3-globin expression. Dr. Jian Xu is a postdoctoral fellow at the Howard Hughes Medical Institute, Children's Hospital Boston (CHB) and his proposed 5-year mentored career plan will be performed in the laboratory of Dr. Stuart Orkin in the Division of Hematology/Oncology at CHB. Dr. Xu's background is in molecular and developmental biology, and his long-term career goal is to become an independent investigator with expertise in basic mechanisms of blood cell development and disorders. Under the mentorship of Dr. Orkin, a recognized leader in the fields of transcriptional regulation, hematopoiesis, and stem cell biology, Dr. Xu has developed a research and training platform that will allow him to acquire the experimental skills and knowledge necessary to be productive in both a mentored and independent setting. To accomplish this, Dr. Xu will take advantage of the expertise and resources of the Orkin lab, acquire additional skills and training in relevant research areas, and establish collaboration with a team of experts. The plan is ideally carried out in the Division of Hematology/Oncology at Children's Hospital Boston, given its distinguished record for training research scientists in a rich and collaborative environment. PUBLIC HEALTH RELEVANCE: The 2-hemoglobin disorders, such as sickle cell anemia and 2-thalassemias, are a major public health problem. Elevated levels of fetal hemoglobin (HbF) are correlated with reduced morbidity and mortality in these diseases. There is great interest in developing approaches to induce HbF expression for therapeutic purposes. The identification and validation of BCL11A as a critical repressor of HbF expression has reinvigorated the field of globin gene regulation. In this proposal, I seek to elucidate the molecular mechanism by which BCL11A controls HbF silencing and hemoglobin switching as a means to targeted reactivation of HbF. I will systematically explore the contribution of BCL11A cooperating factors in the developmental silencing of HbF expression. The findings from these studies will advance our understanding of the role of BCL11A in HbF silencing and provide new clues for target-based therapeutics in patients with the major hemoglobin disorders.