Declining DNA repair in Aging Hematopoietic Stem Cell

描述（由申请人提供）：衰老过程与干细胞池退化相关，导致器官衰竭和功能障碍。动物模型表明DNA修复在维持造血干细胞表型中起着关键作用。例如，失配修复或双链断裂末端连接的缺失导致竞争性再生缺陷和逐渐的干细胞衰竭。在ATM基因缺陷和核苷酸切除修复的小鼠中，也观察到造血干细胞功能障碍。同样，纯化的造血干细胞过表达错配修复蛋白MSH-2和DNA修复支架XRCC-1。随着人类年龄的增长，干细胞表型发生变化，逐渐丧失干细胞数量、再生潜力和应激反应。该提案将评估基因组稳定性的丧失是衰老过程中不可避免的一部分的假设，并且可以通过检查DNA修复途径和功能来测量，从而导致干细胞表型的丧失，再生潜力的丧失和适当应激反应的丧失。在动物模型中观察到，在衰老过程中加速的临床综合征，包括贫血、骨髓衰竭产生单核细胞和全血细胞减少症、免疫失调、骨髓增生异常综合征和白血病，都可能是造血干细胞DNA修复能力进行性丧失的常见病因。

DESCRIPTION (provided by applicant): The aging process is associated with deterioration of the stem cell pool leading to organ failure and dysfunction. Animal models indicate a critical role for DNA repair in the maintenance of the hematopoietic stem cell phenotype. For instance, loss of mismatch repair or double strand break end-joining leads to a competitive repopulation defect and gradual stem cell failure. In mice defective in the ATM gene, and nucleotide excision repair, hematopoietic stem cell dysfunction has also been observed. Likewise, purified hematopoietic stem cells overexpress the mismatch repair protein, MSH-2 and the DNA repair scaffold, XRCC-1. As humans age, the stem cell phenotype changes, with gradual loss of stem cell numbers, regenerative potential and stress response. This proposal will evaluate the hypothesis that loss of genomic stability is an inexorable part of the aging process and is measurable by examining DNA repair pathways and function leads to loss of the stem cell phenotype, loss of regeneration potential and loss of appropriate stress responses. Clinical syndromes that accelerate during aging including anemia, marrow failure yielding mono and pancytopenia, immune dysregulation, myelodysplastic syndromes and leukemias may all have as a common etiology progressive loss of DNA repair capacity in hematopoietic stem cells, as has been observed in animal models. This proposal will develop multiplex assays of a broad range of DNA repair proteins, perform careful assessment of Hematopoietic Stem Cell phenotype and function, and optimize microassays of DNA repair processes in freshly isolated, purified Hematopoietic Stem Cells before and after DNA damage perturbation from the aging population in the decades of 50 to 90. These studies will serve as the prototype with which to analyze normal aging and the diseases associated with aging of hematopoietic stem ceils. Furthermore, these processes undoubtedly affect other tissue stem cells and these approaches may have broad application across stem cell types. These studies will provide the basis to further analysis of DNA repair processes during the aging of stem cells to identify stem cell deficit disorders, response to chemotherapy and other stresses of hematopoietic stem cells land the relation ship between DNA repair processes and stem cell function as measured by conventional and novel assays developed under this RFA.