Base excision repair, premature senescence and aging in Down syndrome

描述（由申请人提供）：唐氏综合征（DS）是一种以加速衰老为特征的智力残疾。该项目的长期目标是 确定唐氏综合征衰老的原因，特别强调研究DNA修复在唐氏综合征衰老表型中的作用。该假说认为，唐氏综合征的衰老表型是由于21号染色体连锁的miRNA过表达诱导的BER终身抑制所致。具体目的1：确定miR-155和/或miR-802单独或组合稳定过表达是否概括了唐氏综合征（DS）的BER和衰老表型。将评价Pol？启动子活性、BER能力和衰老。还将评估MeCP 2和/或Creb 1表达恢复BER的能力。同时，将确定pol缺失对衰老诱导的影响。这将允许建立BER损失和衰老之间的直接联系。具体目标2：确定原代DS成纤维细胞中miR-155或miR-802的沉默是否逆转了DS诱导的BER抑制，以及这是否阻止了早期衰老。这些数据将直接将21号染色体介导的miRNA过表达与BER能力和衰老联系起来。此外，为了测试miRNA过表达是否通过MeCP 2介导的信号传导抑制BER，将在DS系中过表达MeCP 2和CREB 1以确定这是否改善DS的BER表型以及是否可以是适当的干预靶标。具体目标3：唐氏综合征提供了一个独特的机会，研究衰老的作用，作为一个障碍，肿瘤发生在相关的，在体内模型。已知DS的Ts 65 DN小鼠模型重现了大部分DS表型，包括加速老化（在已评价的程度上）和离体成纤维细胞的过早衰老。将在该模型中评价组织随时间推移的全面病理学和形态学分析。此外，我们将确定一组组织中的miR-155和miR-802表达、pol/BER能力和衰老，以开始鉴定哪些组织在DS模型中表现出衰老表型。这些实验将产生关键信息，以证明在该小鼠模型中进行进一步衰老研究和干预策略的合理性。

DESCRIPTION (provided by applicant): Down syndrome (DS) is a condition of intellectual disability characterized by accelerated aging. The broad, long-term objective of this project is to identify the cause(s) of aging in Down syndrome, with a particular emphasis on investigating the role of DNA repair in the aging phenotype observed in Down syndrome. The hypothesis is that the aging phenotype of Down syndrome results from lifelong inhibition of BER induced by chromosome 21-linked miRNA overexpression. This hypothesis will be tested in the following Specific Aims: Specific aim 1: Determine whether miR-155 and/or miR-802 stable overexpression alone or in combination recapitulate the BER and senescence phenotypes of Down syndrome (DS). Pol¿ promoter activity, BER capacity, and senescence will be evaluated. The ability of MeCP2 and/or Creb1 expression to restore BER will also be evaluated. In parallel the impact of pol¿ nullizygosity on senescence induction will be determined. This will allow a directly connection between BER loss and senescence to be established. Specific aim 2: Determine whether silencing of either miR-155 or miR-802 in primary DS fibroblasts reverses the DS-induced inhibition of BER and whether that then prevents early senescence. These data would directly tie chromosome 21-mediated miRNA overexpression to BER capacity and senescence. Further, to test whether miRNA overexpression inhibits BER through MeCP2-mediated signaling, MeCP2 and CREB1 will be overexpressed in DS lines to determine both whether this ameliorates the BER phenotype of DS and whether either may be an appropriate interventional target. Specific aim 3: Down syndrome provides a unique opportunity to investigate the role of senescence as a barrier to tumorigenesis in a relevant, in vivo model. The Ts65DN mouse model of DS is known to recapitulate much of the DS phenotype, including accelerated aging (to the extent it has been evaluated) and premature senescence in ex vivo fibroblasts. Thorough pathological and morphological analysis of tissues over time will be evaluated in this model. In addition we will determine miR-155 and miR-802 expression, pol¿/BER capacity and senescence in a panel of tissues to begin to identify which tissues exhibit aging phenotypes in the DS model. These experiments will generate critical information to justify further aging studies and interventional strategies in this mouse model.