ELUCIDATING THE ROLE OF KRUPPEL LIKE FACTOR 7 IN T CELL DEVELOPMENT

描述(由申请者提供)：本申请提出了一个为期4年的计划，为候选人提供有指导的研究和职业发展培训。应聘者最近完成了为期3年的K12奖(儿科科学家发展计划)，并希望获得更多的指导支持，以促进她的科学和职业目标。的最终目标是 应聘者将成为一家学术医学中心的独立研究员，研究调节正常和恶性造血的因素。本申请中概述的实验旨在了解转录因子Kruppel like factor7(KLF7)在T细胞发育中的作用。拟议的研究将在华盛顿大学的丹尼尔·林克博士的主要指导下进行，丹尼尔·林克博士是造血领域的领军人物，也是一位经验丰富、备受尊敬的导师。由于拟议的研究对候选人来说是一种新的研究途径，胸腺细胞发育专家江川武博士将担任共同导师，并提供T细胞研究的技术指导。KLF7在治疗耐药的儿童ALL中的表达增加，是复发疾病的独立预测因素(Flotho等人，血液2007)。KLF转录因子家族参与了血细胞发育的许多方面；然而，KLF7在造血中的作用以前还没有被描述。由于KLF7靶基因包括几个与造血干/祖细胞(HSPC)维持有关的基因，我们推测KLF7可能在调节正常的HSPC功能中发挥作用，并可能与白血病的发生或治疗耐药有关。我们在初步数据中显示，在增强KLF7表达的同时，显著抑制HSC的再繁殖和自我更新能力，导致T细胞的相对保存，抗凋亡因子BCL2A1的表达增加，以及CD4-CD8-(DN)胸腺细胞的凋亡减少。KLF7在T细胞发育过程中都有表达，在胸腺细胞发育的CD4+CD8+(DP)阶段达到顶峰。KLF7的丢失与早期胸腺细胞数量的减少有关。根据我们的初步数据和KLF家族在调节T细胞中的突出作用，我们假设KLF7调节胸腺细胞的发育和对T细胞谱系的承诺。此外，KLF7的过表达抑制了早期胸腺细胞的凋亡，可能是ALL化疗耐药的原因之一。提出的具体目标是：1)确定KLF7是否指导多能祖细胞对T细胞命运的承诺；以及2)确定KLF7对胸腺细胞存活、增殖和成熟的贡献。此外，我们建议在胸腺细胞中鉴定KLF7的靶点，并进一步阐明BCL2A1在过度表达KLF7的糖尿病肾病胸腺细胞存活中的作用。未来的研究将调查已确定的靶点在T细胞发育中的作用，以及在潜在地介导白血病细胞的治疗耐药性方面的作用。最终，抑制KLF7或其下游靶点可能被用于增敏化疗耐药细胞，为难治性或复发白血病的治疗提供了一种有针对性的方法。

DESCRIPTION (provided by applicant): This application proposes a 4-year plan to provide the candidate with mentored research and career development training. The candidate has recently completed a 3-year K12 award (Pediatric Scientist Development Program), and desires additional mentored support to facilitate her scientific and career goals. The ultimate goal of the candidate is to be an independent investigator at an academic medical center, studying factors that regulate normal and malignant hematopoiesis. The experiments outlined in this application aim to understand the role of the transcription factor Kruppel like factor 7 (KLF7) in T cell development. The proposed studies will be carried out at Washington University under the primary mentorship of Dr. Daniel Link, a leader in the field of hematopoiesis and a highly experienced and regarded mentor. As the proposed studies are a new avenue of study for the candidate, Dr. Takeshi Egawa, an expert in thymocyte development, will serve as a co-mentor and provide technical guidance on the study of T cells. Expression of KLF7 is increased in therapy-resistant pediatric ALL and is an independent predictor of relapsed disease (Flotho, et al; Blood 2007). The KLF family of transcription factors is involved in numerous aspects of blood cell development; however a role for KLF7 in hematopoiesis has not been previously described. Since KLF7 target genes include several implicated in hematopoietic stem and progenitor (HSPC) maintenance, we hypothesized that KLF7 may play a role in regulating normal HSPC function, and may contribute to leukemogenesis or therapy resistance. We show in preliminary data that enforced expression of KLF7, while markedly inhibiting HSC repopulating and self-renewal capacities, results in the relative preservation of T cells, increased expression of the anti-apoptotic factor BCL2A1, and reduced apoptosis of CD4- CD8-(DN) thymocytes. KLF7 is expressed throughout T cell development, peaking at the CD4+ CD8+ (DP) stage of thymocyte development. Loss of KLF7 is associated with decreased numbers of early thymocytes. Based on our preliminary data and the prominent role of the KLF family in regulating T cells, we hypothesize that KLF7 regulates thymocyte development and commitment to the T cell lineage. Furthermore, overexpression of KLF7 suppresses apoptosis of early thymocytes and may contribute to chemotherapy resistance in ALL. The specific aims proposed are: 1) Determine whether KLF7 directs the commitment of multipotent progenitor cells to a T cell fate; and 2) Determine the contribution of KLF7 to thymocyte survival, proliferation and maturation. In addition, we propose to identify targets of KLF7 in thymocytes, and to further elucidate the role of BCL2A1 in mediating the survival of DN thymocytes overexpressing KLF7. Future studies will investigate the role of the identified targets in T cell development and in potentially mediating the therapy-resistance of leukemia cells. Ultimately, inhibition of KLF7 or its downstream targets could potentially be used to sensitize chemotherapy- resistant cells, providing a targeted approach to the treatment of refractory or relapsed leukemia.