Mechanisms of STAT5 function in hematopoietic stem and progenitor cells

描述（申请人提供）：我们的实验室已经研究了十多年的信号换能器和转录激活因子5 （STAT5）在造血中的作用，我们已经确定了在造血和免疫细胞生物学中的重要作用。尽管在了解缺乏STAT5的小鼠的严重程度和广泛缺陷方面取得了这些进展，但STAT5介导的转录激活控制造血的机制尚未完全确定。我们最近报道，尽管STAT5驱动多谱系分化，但它在促进造血干细胞静止中起着令人惊讶的作用。我们已经确定了参与这一过程的关键靶基因，包括tie2和p57。造血干细胞与祖细胞的氧化电位存在较大差异，STAT5对活性氧和活性氮十分敏感。我们将探索STAT5介导的缺氧造血干细胞生态位中的转录激活与氧化促造血祖生态位中的转录激活是独特的，STAT5功能的变化依赖于微环境，可以控制植入、动员、谱系分化和静止。我们已经对STAT5缺失的c-Kit+Sca-1+Lin- (KLS)细胞进行了初步的基因表达阵列分析，并利用染色质免疫沉淀法鉴定出bcl2是一种新的STAT5直接靶基因。因此，我们将测试以下目标：1)我们将使用一种新的可行的造血特异性条件敲除小鼠来研究STAT5如何调节小生境的幼体播种、迁移和动员。2)我们已经证明，长期再生的造血干细胞库对STAT5缺失非常敏感，而短期再生的造血干细胞库则不受STAT5缺失的影响。我们将分析stat5缺陷小鼠的谱系分化，并描述淋巴细胞启动和b系急性淋巴细胞白血病的易感性。3)我们将在多能造血细胞中进行STAT5 ChIP-qPCR实验，确定其氧化还原调控机制。总的来说，这三个目标将为STAT5对早期作用细胞因子的造血功能和分子调控提供重要的见解，并可能导致改善血液疾病的治疗方法。

DESCRIPTION (provided by applicant): Our lab has been studying the role of signal transducer and activator of transcription 5 (STAT5) in hematopoiesis for more than a decade and we have identified important roles in hematopoietic and immune cell biology. Despite these advances in understanding the severity and broad range of defects in mice lacking STAT5, the mechanisms by which STAT5-mediated transcriptional activation controls hematopoiesis are not fully defined. We recently reported that although STAT5 drives multilineage differentiation it plays a surprising role in promoting hematopoietic stem cell quiescence. We have already identified key target genes involved in this process, including tie2 and p57. There are big differences between the hematopoietic stem cell and progenitor niches in regard to their oxidation potential and STAT5 is sensitive to reactive oxygen and nitrogen species. We will explore the overall hypothesis that STAT5-mediated transcriptional activation in the hypoxic hematopoietic stem cell niche is unique from that in the oxidation promoting hematopoietic progenitor niche and that changes in STAT5 function depend on the microenvironment and can control engraftment, mobilization, lineage differentiation, and quiescence. We have already performed preliminary gene expression array analysis of STAT5-deficient c-Kit+Sca-1+Lin- (KLS) cells and have utilized chromatin immunoprecipitation assays that identified bcl2 as a novel STAT5 direct target gene. Therefore we will test the following aims: 1) We will use a novel viable hematopoietic-specific conditional knockout mouse to study how STAT5 modulates juvenile seeding of the niches, migration, and mobilization. 2) We have demonstrated that the long-term repopulating hematopoietic stem cell pool is uniquely sensitive to STAT5 deletion, whereas the short-term repopulating pool is spared. We will analyze lineage differentiation in STAT5-deficient mice and characterize lymphoid priming and predisposition to B-lineage acute lymphoblastic leukemia. 3) We will perform STAT5 ChIP-qPCR experiments in multipotent hematopoietic cells and identify mechanisms of redox regulation. Collectively, these three aims will provide important insight into the functional and molecular regulation of hematopoiesis by STAT5 in response to early acting cytokines and may lead to improved therapeutic approaches for treating blood disorders.