ROLE OF THE CHROMATIN REGULATOR, MLL, IN T CELL DEVELOPMENT

染色质调节因子 MLL 在 T 细胞发育中的作用

• 批准号: 7720751
• 负责人: Patricia Ernst
• 金额: $ 23.51万
• 依托单位: DARTMOUTH COLLEGE
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-07-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7720751
• 关键词: Acute; Acute Lymphocytic Leukemia; Acute T Cell Leukemia; Adult; Animals; Area; B-Lymphocytes; Backcrossings; Biological Models; Bone Marrow; Bone Marrow Cells; Cell Count; Cells; Cessation of life; Chromatin; Computer Retrieval of Information on Scientific Projects Database; Coupled; Development; Double-Stranded RNA; Embryo; Erythroid; Fetal Liver; Funding; Genes; Goals; Grant; Greater sac of peritoneum; Hematopoiesis; Hematopoietic; Hematopoietic System; Hematopoietic stem cells; Infant; Injection of therapeutic agent; Institution; Lymphoid; Lymphopoiesis; Maintenance; Manuscripts; Modeling; Mouse Strains; Muramidase; Mus; Pancytopenia; Patients; Phenotype; Population; Research; Research Personnel; Resources; Role; Source; Stem cells; T-Lymphocyte; Transgenes; Transgenic Animals; Transgenic Organisms; United States National Institutes of Health; analog; cell type; day; exhaustion; interest; mature animal; primitive cell; progenitor; recombinase; research study; size; stem

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. To develop model systems in which the role of MLL can be assessed during adult hematopoiesis and lymphopoiesis, we have developed a loxP-flanked version of the murine Mll gene, backcrossed this strain, and crossed it to the Mx1-Cre transgenic strain. The Mx1 transgene is induced by the injection of polyI:polyC, a double stranded RNA analog that can be injected into the peritoneal cavity of adult animals. This approach allowed us to study the effect of Mll deletion in an acute setting. Using this model, we demonstrated that the maintenance of hematopoietic stem and progenitor populations depend on Mll for their homoestasis. We demonstrated that this was likely due to two different cell-context dependent roles of Mll in these primitive cell types. First, Mll deletion in hematopoietic stem cells resulted in their escape from quiescence and an increase in proliferation, coupled to symmetric differentiation of progeny cells. This resulted in the rapid exhaustion of stem cell activity from the bone marrow. Second, we demonstrated that in myelo-erythroid progenitors, Mll deficiency resulted in the reduction in proliferation resulting in reduced progenitor pool sizes. Together, these alterations resulted in the rapid decline in bone marrow cell numbers upon Mll deletion and ultimately bone marrow failure and animal death. Surprisingly, when we crossed the Mll loxP flanked strain to Cre transgenic animals that express Cre only in differentiating lineages (T cells [lck-Cre], B cells [CD19-Cre] or myelomonocytic precursors [lysozyme M-Cre]), we found that there was no effect on steady state cell numbers, demonstrating that Mll is only essential in the early stem and progenitor populations. Progress toward the main goal of this Project has been great in the area of lymphopoiesis. We are currently finishing experiments that will form the bulk of a manuscript that defines a block in B lymphopoiesis in the absence of Mll. To perform these studies, we obtained a Vav-Cre strain of mice from Dr. T. Graf (via Dr. H. Mikkola). This strain expresses the Cre recombinase within the hematopoietic system starting at embryonic day 13 in the fetal liver. Using this approach, we are able to study the early steps in commitment to the lymphoid lineages (T and B cells) which was not possible using the Mx1-Cre strain used in the studies described above, due to the confounding effects of polyI:polyC injection. With the Vav-cre model, we observe a stringent requirement for MLL in B lymphopoiesis but not T lymphopoiesis. This is interesting since patients with MLL translocations, particularly infants, have acute lymphocytic leukemia (ALL) of an early B cell phenotype and T cell ALL is very rare.

该副本是利用众多研究子项目之一 由NIH/NCRR资助的中心赠款提供的资源。子弹和 调查员（PI）可能已经从其他NIH来源获得了主要资金， 因此可以在其他清晰的条目中代表。列出的机构是 对于中心，这不一定是调查员的机构。 为了开发模型系统，其中可以在成年造血和淋巴细胞中评估MLL的作用，我们开发了鼠MLL基因的Loxp-Flankp-Flanks版本，将这种菌株交叉并将其交叉至MX1-CRE转基因菌株。 MX1转基因是通过注射Polyi：PolyC的诱导的，PolyC是一种双链RNA类似物，可以注射到成年动物的腹膜腔中。 这种方法使我们能够在急性环境中研究MLL缺失的效果。 使用此模型，我们证明了造血茎和祖细胞种群的维持取决于其同源性的MLL。 我们证明，这可能是由于MLL在这些原始细胞类型中的两个不同细胞上下文依赖性作用所致。 首先，造血干细胞中的MLL缺失导致它们摆脱静止和增殖增加，并与后代细胞的对称分化结合。 这导致了骨髓的干细胞活性快速耗尽。 其次，我们证明了在骨髓瘤祖细胞中，MLL缺乏导致增殖减少，从而减少祖细胞池的大小。 共同发生这些改变导致MLL缺失后骨髓细胞数量迅速下降，最终导致骨髓衰竭和动物死亡。 Surprisingly, when we crossed the Mll loxP flanked strain to Cre transgenic animals that express Cre only in differentiating lineages (T cells [lck-Cre], B cells [CD19-Cre] or myelomonocytic precursors [lysozyme M-Cre]), we found that there was no effect on steady state cell numbers, demonstrating that Mll is only essential in the early stem and progenitor populations. 在淋巴管道领域，朝着该项目的主要目标取得了进步。 我们目前正在完成实验，这些实验将形成大部分手稿，该手稿在没有MLL的情况下定义了B淋巴管中的一个块。 为了进行这些研究，我们从T. Graf博士（通过H. Mikkola博士）获得了VAV-CRE菌株。 该菌株从胎儿肝脏的胚胎第13天开始造血系统中的CRE重组酶。 使用这种方法，我们能够研究对淋巴样谱系（T和B细胞）承诺的早期步骤，由于Polyi注射Polyi的混杂作用，因此使用上述研究中使用的MX1-CRE菌株不可能使用。使用VAV-CRE模型，我们观察到B淋巴管中的MLL的严格要求，而不是T淋巴管菌。 这很有趣，因为患有MLL易位的患者，尤其是婴儿，患有早期B细胞表型的急性淋巴细胞性白血病（所有）和T细胞都非常罕见。