Mechanisms of STAT5 function in hematopoietic stem and progenitor cells

描述（由申请人提供）：我们的实验室已经研究信号转导子和转录激活子5（STAT 5）在造血中的作用超过十年，我们已经确定了造血和免疫细胞生物学中的重要作用。尽管在理解缺乏STAT 5的小鼠中缺陷的严重性和广泛性方面取得了这些进展，但STAT 5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，虽然STAT 5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tie 2和p57。造血干细胞和祖细胞之间在其氧化电位方面存在很大差异，并且STAT 5对活性氧和氮物种敏感。我们将探讨的总体假设，即STAT 5介导的转录激活在缺氧造血干细胞龛是独特的，从氧化促进造血祖细胞龛和STAT 5功能的变化取决于微环境，可以控制植入，动员，谱系分化和静止。我们已经对STAT 5缺陷的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试验鉴定了bcl 2作为新型STAT 5直接靶基因。因此，我们将测试以下目标：1）我们将使用新的可行的造血特异性条件性敲除小鼠来研究STAT 5如何调节小生境的幼年播种、迁移和动员。2)我们已经证明，长期再生造血干细胞库是唯一敏感的STAT 5删除，而短期再生池是幸免。我们将分析STAT 5缺陷小鼠的谱系分化，并描述淋巴启动和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STAT 5 ChIP-qPCR实验，并确定氧化还原调节的机制。总的来说，这三个目标将提供重要的洞察造血功能和分子调控的STAT 5响应于早期作用的细胞因子，并可能导致改善的治疗方法，用于治疗血液疾病。

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.