SATB1-dependent epigenetic regulation of leukemia initiating cells

描述（由申请人提供）：在造血系统中，特定转录因子的相互作用指导正常造血干细胞（HSC）以精确的方式发挥功能。虽然已知这些转录网络中特定因子的表达失调会破坏正常的HSC功能并导致白血病起始细胞（LIC）的形成，但表观遗传机制的超基因表达调控仍然知之甚少。我们和其他人已经确定了一种特殊的染色质重塑因子，特殊的富含at的序列结合蛋白1 （SATB1）是控制正常t细胞和髓细胞分化以及白血病基因表达的重要表观遗传因子。我们的初步数据显示：SATB1是HSC自我更新功能所必需的，髓系主调控因子PU.1上游调控元件SATB1结合位点的序列改变在AML中起疾病调节剂的作用，而SATB1在正常造血干细胞和祖细胞中高表达，但在AML患者源性LIC中表达受损。我们假设这种染色质重塑蛋白调节正常HSC和恶性干细胞的功能。由于表观遗传改变不会改变DNA序列，并且在药理学上是可逆的，因此它们被认为是有希望的治疗靶点。我们建议研究染色质重塑蛋白SATB1在HSC和LIC中的表观遗传调控作用。satb1依赖性基因表达调控在HSC和LIC中的功能将通过体内模型（如干细胞移植试验）进行表征。此外，这些功能研究将伴随着综合的表观基因组分析，研究satb1依赖性HSC和LIC调节的机制。我们将利用全球染色质免疫沉淀分析（ChIP-seq）结合基因表达和DNA甲基化模式分析。鉴于我们观察到SATB1在AML患者LIC中下调，SATB1与低亲和力结合位点的结合可能会被取消，从而导致LIC形成或维持相关基因的表达改变。我们将恢复AML患者源性LIC中SATB1的表达，并评估这是否具有抗白血病作用。我们将通过ChIP-seq结合基因表达谱来表征SATB1低表达和恢复SATB1表达的AML LIC中的SATB1结合模式。差异占据和表达的基因将进一步进行功能分析，以确定其作为治疗靶点的潜在用途。我们的初步数据使SATB1成为白血病干细胞中肿瘤抑制基因表观遗传调控的潜在范例。我们的研究将有助于阐明新的分子途径，这些途径可以用于开发以lic为导向的表观遗传治疗方法。

DESCRIPTION (provided by applicant): In the hematopoietic system, the interplay of particular transcription factors instructs normal hematopoietic stem cells (HSC) to function in a precise manner. While it is known that expression deregulation of specific factors in these transcriptional networks disrupts normal HSC function and leads to the formation of leukemia initiating cells (LIC), superordinate gene expression regulation by epigenetic mechanisms, is still poorly understood. We and others have identified a particular chromatin remodeling factor, special AT-rich sequence-binding protein 1 (SATB1) as an important epigenetic factor governing gene expression in normal T-cell and myeloid differentiation, and in leukemia. Our preliminary data show: SATB1 is required for self-renewal function of HSC, sequence alterations within the SATB1-binding site of an upstream regulatory element of the myeloid master regulator PU.1 act as disease modifiers in AML, and while SATB1 is highly expressed in normal hematopoietic stem and progenitor cells, its expression is impaired in AML patient-derived LIC. We hypothesize that this chromatin remodeling protein regulates the function of normal HSC and malignant stem cells. Since epigenetic alterations do not change the DNA sequences and are pharmacologically reversible, they have been regarded as promising targets for therapy. We propose to investigate epigenetic gene regulation by the chromatin-remodeling protein SATB1 in HSC and LIC. The function of SATB1-dependent gene expression regulation in HSC and LIC will be characterized using in vivo models, such as stem cell transplantation assays. Additionally, these functional studies will be accompanied with integrated epigenomic analyses investigating the mechanism of SATB1-dependent HSC and LIC regulation. We will utilize global chromatin immunoprecipitation analysis (ChIP-seq) in combination with gene expression and DNA methylation pattern analysis. Given our observation that SATB1 is down- regulated in LIC of AML patients, binding of SATB1 to low affinity binding sites may be abrogated and cause expression changes of genes involved in the formation or maintenance of LIC. We will restore SATB1 expression in AML patient-derived LIC and evaluate whether this has an anti-leukemic effect. We will characterize SATB1 binding patterns in AML LIC with low and restored SATB1 expression by ChIP-seq combined with gene expression profiling. Genes differentially occupied and expressed will be further functionally analyzed to determine their potential use as therapeutic targets. Our preliminary data make SATB1 a potential paradigm for epigenetic regulation of tumor suppressor genes in leukemia stem cells. Our study will contribute to elucidating novel molecular pathways that can be targeted for the development of LIC-directed epigenetic therapeutic approaches. PUBLIC HEALTH RELEVANCE: Project Narrative Our study will investigate the function of special AT-rich sequence-binding protein 1 (SATB1), a DNA- organizing ('epi-genetic') factor we have found in normal blood stem cells and cells that initiate acute myeloid leukemia (AML). Our preliminary data show that the presence of SATB1 is required to ensure normal blood stem cell function and our observations further suggest that SATB1 critically contributes not only to the function of normal blood stem cells, but also cells that initiate leukemia. The results of our study will add to our current understanding of normal blood cell production and will also identify fundamentally novel pathways and targets for specific, leukemia initiating cell-directed therapies.