Base excision repair, premature senescence and aging in Down syndrome

描述(申请人提供)：唐氏综合症(DS)是一种以加速衰老为特征的智力残疾状况。该项目的广泛、长期目标是 确定唐氏综合症衰老的原因(S)，特别强调研究DNA修复在唐氏综合症观察到的衰老表型中的作用。假设唐氏综合征的衰老表型是由21号染色体连锁的miRNA过度表达导致的BER终生抑制的结果。这一假设将在以下特定目标中得到验证：特定目标1：确定miR-155和/或miR-802稳定过表达是单独还是联合反映唐氏综合征(DS)的误码率和衰老表型。将对POL？启动子活性、BER容量和衰老进行评估。还将评估MeCP2和/或Creb1表达恢复误码率的能力。同时，将确定Polo？无效合子对衰老诱导的影响。这将允许在误码率损失和衰老之间建立直接联系。具体目标2：确定在原代DS成纤维细胞中沉默miR-155或miR-802是否逆转DS诱导的BER抑制，以及是否随后防止早期衰老。这些数据将直接将21号染色体介导的miRNA过度表达与误码率能力和衰老联系起来。此外，为了测试miRNA过表达是否通过MeCP2介导的信号转导抑制BER，将在DS系中过表达MeCP2和CREB1，以确定这是否改善DS的BER表型，以及两者是否可能是合适的干预靶点。具体目标3：唐氏综合征提供了一个独特的机会，在相关的体内模型中研究衰老作为肿瘤发生障碍的作用。众所周知，Ts65Dn小鼠的DS模型概括了DS的大部分表型，包括加速衰老(根据评估的程度)和体外成纤维细胞的早衰。在这个模型中，将对组织随着时间的推移进行彻底的病理和形态分析。此外，我们将测定一组组织中miR-155和miR-802的表达、Polo？/BER容量和衰老，以开始识别DS模型中哪些组织表现出衰老表型。这些实验将产生关键信息，以证明在这个小鼠模型中进一步的衰老研究和干预策略是合理的。

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.