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: 7959994
• 负责人: Patricia Ernst
• 金额: $ 8万
• 依托单位: DARTMOUTH COLLEGE
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2010-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7959994
• 关键词: Adult; Alleles; Animals; B-Lymphocytes; Backcrossings; Biochemical; Bone Marrow; Bone Marrow Cells; CREB1 gene; Cell Count; Cells; Cessation of life; Chromatin; Chromosomal translocation; Collaborations; Computer Retrieval of Information on Scientific Projects Database; Coupled; Development; Erythroid; Funding; Genes; Grant; Hematopoiesis; Hematopoietic; Hematopoietic System; Hematopoietic stem cells; Institution; MLL gene; Maintenance; Modeling; Molecular; Mouse Strains; Muramidase; Mus; Nuclear; Pancytopenia; Population; Proto-Oncogenes; Research; Research Personnel; Resources; Role; Source; Stem cells; T-Cell Activation; T-Cell Development; T-Lymphocyte; Transgenic Animals; United States National Institutes of Health; cell type; exhaustion; leukemia; primitive cell; progenitor; recombinase; 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. My group aims to understand the normal function of the MLL proto-oncogene particularly during the development and function of the hematopoietic system. The MLL gene encodes a large nuclear chromatin regulator that is disrupted in common chromosomal translocations found in leukemia. To study the normal role of MLL during hematopoiesis, we have developed a loxP-flanked allele of the murine Mll gene, backcrossed this strain and crossed these animals to either inducible or lineage-specific Cre recombinase mouse strains. This approach allowed us to study the effect of Mll loss on multiple hematopoietic cell types during adult steady state hematopoiesis. Using this model, we demonstrated that the maintenance of hematopoietic stem and progenitor populations absolutely depends on Mll. 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. In the current proposal, we focused on a potential independent MLL function in T cell activation, as we had demonstrated a biochemical collaboration between domains within MLL and the sequence-specific activator CREB, which is known to function in T cell activation.

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 我的团队旨在了解MLL原癌基因的正常功能，特别是在造血系统的发育和功能过程中。MLL基因编码一种大的核染色质调节因子，在白血病常见的染色体易位中被破坏。为了研究MLL在造血过程中的正常作用，我们开发了小鼠MLL基因的loxP侧翼等位基因，回交该品系，并将这些动物与可诱导的或谱系特异性的Cre重组酶小鼠品系杂交。这种方法使我们能够研究MLL丢失对成人稳态造血过程中多种造血细胞类型的影响。利用这一模型，我们证明了造血干/祖细胞群的维持完全依赖于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的细胞上下文依赖角色。首先，造血干细胞中MLL的缺失导致它们摆脱静止状态，增加增殖，并伴随着子代细胞的对称分化。这导致了骨髓中干细胞活性的迅速耗尽。第二，我们证明在骨髓红系祖细胞中，MLL缺乏导致增殖减少，导致祖细胞池大小减小。总之，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。令人惊讶的是，当我们将MLL loxP侧翼株与仅在分化谱系(T细胞[Lck-Cre]、B细胞[CD19-Cre]或骨髓单核细胞前体[Lysozyme M-Cre])中表达Cre的转基因动物杂交时，我们发现对稳定状态的细胞数量没有影响，表明MLL只在早期干祖细胞群中是必需的。在目前的方案中，我们将重点放在T细胞激活中潜在的独立MLL功能上，因为我们已经证明了MLL中的结构域与序列特异性激活剂CREB之间的生化协作，CREB已知在T细胞激活中发挥作用。