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的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 我的小组旨在了解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基因编码一个大的核染色质调节因子，在白血病中发现的常见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，我们开发了鼠MLL基因的loxP侧翼等位基因，将该品系回交并将这些动物与诱导型或谱系特异性Cre重组酶小鼠品系杂交。该方法允许我们研究MII损失对成人稳态造血期间多种造血细胞类型的影响。 使用该模型，我们证明了造血干细胞和祖细胞群体的维持绝对依赖于MII。 我们证明，这可能是由于MII在这些原始细胞类型中的两种不同的细胞环境依赖性作用。 首先，造血干细胞中的MII缺失导致它们从静止中逃逸并增加增殖，与子代细胞的对称分化偶联。 这导致骨髓中的干细胞活性迅速耗尽。 其次，我们证明了在骨髓-红系祖细胞中，MII缺乏导致增殖减少，从而导致祖细胞库大小减少。 总之，这些改变导致MII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MII loxP侧翼菌株与仅在分化谱系（T细胞[lck-Cre]、B细胞[CD 19-Cre]或骨髓单核细胞前体[溶菌酶M-Cre]）中表达Cre的Cre转基因动物杂交时，我们发现对稳态细胞数量没有影响，证明MII仅在早期干细胞和祖细胞群体中是必需的。 在目前的提案中，我们专注于T细胞活化中潜在的独立MLL功能，因为我们已经证明了MLL内的结构域与序列特异性激活剂CREB之间的生物化学协作，该序列特异性激活剂CREB已知在T细胞活化中起作用。