Mechanisms of age-associated cardiac heterochromatin dysfunction

大量证据表明：1）表观遗传改变是衰老的保守特征，2）它们 有助于年龄相关的功能下降，和3）操纵表观遗传调节因子可以显着 增加健康和寿命。然而，关于年龄相关的表观遗传机制的知识 变化还远未完成。这项提案的重点是阐明与年龄相关的改变的基础， 心脏异染色质主要卫星重复序列（MSR）是异染色质中的关键成分， 老鼠. 25年前，人们注意到MSR抑制随着小鼠心脏的衰老而减弱。的 这种效应的分子基础从未被阐明。此外，这种去压抑的功能性影响 目前尚不清楚，尽管在其他情况下，MSR沉默的丧失与受损的染色体 分离和发展的非整倍体，非二倍体细胞的染色体内容。长期目标是 了解染色质功能随年龄变化的机制和功能后果。的 本申请的目的是阐明与年龄相关的心脏MSR去抑制的基础，并测试 对心脏基因组稳定性的影响。支持性研究可能将这种效应与神经系统功能降低联系起来。 NAD+依赖性脱乙酰酶SIRT1。假设是由于SIRT1功能的减少， 在衰老的心脏NAD+水平，进而导致受损的MSR异染色质结构和转录 去压抑进一步提出，MSR异染色质的失调有助于年龄相关的细胞凋亡。 心脏非整倍化这些研究的基本原理是，表观遗传变化是可逆的，至少在 原则因此，对年龄相关的异染色质改变的机制性了解可能会发现新的 治疗机会在返老还童医学。这项工作将在两个具体的 目标。首先，NAD+水平和SIRT1活性降低在年龄相关的MSR去抑制中的潜在作用， 将被评估。这一目标将通过染色质免疫沉淀，免疫荧光， 微球菌核酸酶研究，分析不同年龄的小鼠，以及具有遗传或药理学 老年心肌中NAD+水平或SIRT1功能的重建。二、功能受损的影响 将在年龄相关心脏非整倍体化的背景下评估MSR异染色质化。细胞 将开发基于培养的系统，以严格测试SIRT1活性、MSR 表达和维持整倍性。这项建议是创新的，因为与年龄有关的损失的基础 心脏MSR沉默的可能性仍然未知。这项工作是有意义的，因为它将提供机械的见解 染色质和衰老生物学中的一个25年之谜。根据公布的数据显示， 心脏整倍体的维持与后期功能的改善有关， 该提案可能为改善老年人心脏健康的新型治疗干预提供了见解。 个体

A large body of evidence indicates that 1) epigenetic alterations are a conserved feature of aging, 2) they contribute to age-associated functional decline, and 3) manipulation of epigenetic regulators can markedly increase health- and lifespan. However, knowledge regarding mechanisms of age-associated epigenetic changes is far from complete. This proposal focuses on elucidating the basis for age-associated alterations in cardiac heterochromatin. The major satellite repeats (MSRs) are a key heterochromatin component in the mouse. Twenty-five years ago, it was noted that MSR repression is attenuated with aging in mouse heart. The molecular basis for this effect has never been elucidated. Moreover, the functional impact of this derepression is unclear, although in other contexts loss of MSR silencing is associated with impaired chromosomal segregation and development of aneuploidy, a non-diploid cellular chromosomal content. The long-term goal is to understand both mechanisms and functional consequences of altered chromatin function with age. The objective of this application is to elucidate the basis for age-associated cardiac MSR derepression, and to test its impact on cardiac genomic stability. Supporting studies potentially link this effect to reduced function of the NAD+-dependent deacetylase SIRT1. The hypothesis is that acquired loss of SIRT1 function, due to reductions in NAD+ levels in the aging heart, lead in turn to impaired MSR heterochromatin structure and transcriptional derepression. It is further proposed that dysregulation of MSR heterochromatin contributes to age-associated cardiac aneuploidization. The rationale for these studies is that epigenetic changes are reversible, at least in principle. Therefore, mechanistic insight into age-associated heterochromatin alterations may identify novel therapeutic opportunities in rejuvenative medicine. The work will be carried out in the context of two Specific Aims. First, the potential role of reduced NAD+ levels and SIRT1 activity in age-associated MSR derepression will be assessed. This Aim will be carried out via chromatin immunoprecipitation, immunofluorescence, and micrococcal nuclease studies, analyzing mice of varied ages, and strains with genetic or pharmacological reconstitution of NAD+ levels or SIRT1 function in aged myocardium. Second, the functional impact of impaired MSR heterochromatinization will be assessed in the context of age-associated cardiac aneuploidization. A cell culture-based system will be developed to rigorously test functional relationships between SIRT1 activity, MSR expression, and maintenance of euploidy. This proposal is innovative, since the basis for age-associated loss of cardiac MSR silencing remains unknown. The work is significant, in that it will provide mechanistic insight into a 25-year old mystery in chromatin and aging biology. In light of published data showing that enhanced euploidy maintenance in the heart is associated with improved function at later ages, the studies in this proposal may provide insight into novel therapeutic interventions to ameliorate cardiac health in older individuals.