Understanding the mechanisms that modulate the effects of mutant Huntingtin lowering in aging Huntington's disease model mice

了解调节衰老亨廷顿病模型小鼠突变亨廷顿蛋白降低效应的机制

• 批准号: 10556339
• 负责人: Scott Zeitlin
• 金额: $ 41.5万
• 依托单位: UNIVERSITY OF VIRGINIA
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-02-01 至 2027-01-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10556339
• 关键词: 20q; Actins; Affect; Age; Age Months; Aging; Alleles; Antisense Oligonucleotides; Astrocytosis; Attenuated; Behavioral; Brain; Brain region; Cell Nucleus; Cell physiology; Cognitive; Corpus striatum structure; DNA Damage; DNA Repair; Deep Cervical Lymph Node; Disease; Disease Progression; Disease model; Elements; Encephalitis; Future; Gene Expression; Genes; Gliosis; Huntington Disease; Huntington gene; Impairment; Inflammasome; Introns; Isopropyl Thiogalactoside; Kinetics; Knock-in; Lac Repressors; Ligation; Long-Term Effects; Lymphatic function; Measures; Meningeal lymphatic system; MicroRNAs; Modeling; Monitor; Motor; Mus; Mutation; Neurodegenerative Disorders; Nuclear Inclusion; Onset of illness; Outcome; Pathogenesis; Pathway interactions; Phase III Clinical Trials; Phenotype; Physiological; Proteins; Quantitative Reverse Transcriptase PCR; RNA; RNA Splicing; Reporter; Safety; Single-Stranded DNA; Site; Stains; Stretching; Symptoms; System; Testing; Therapeutic; Therapeutic Intervention; Therapeutic Uses; Time; Transcript; Transcription Initiation Site; Transgenes; Trinucleotide Repeats; Withdrawal; age related; aged; aging brain; autosome; behavioral phenotyping; cohort; cytokine; efficacy testing; gain of function; genetic signature; insight; knock-down; lymphatic drainage; motor symptom; mouse model; mutant; neuroinflammation; neuropathology; oxidative DNA damage; polyglutamine; preclinical study; promoter; repaired; response; therapeutic development; therapeutic target; transcriptome

Huntington’s disease (HD) is an autosomal dominant neurodegenerative disorder that is caused by the expansion of a CAG triplet repeat encoding a stretch of polyglutamine (polyQ) within Huntingtin (HTT), the protein product of the HD gene. The HD mutation confers a deleterious gain-of-function, possibly via the expression of both toxic RNA transcripts and protein, together with potential loss of normal HTT function that affects a variety of cellular functions. A number of HTT lowering strategies are being developed–Phase III clinical trials testing the efficacy of anti-sense oligonucleotides (ASOs) targeting either total HTT expression or selectively mutant HTT (mHTT) expression are underway, while Htt lowering using other approaches (miRNA and splicing modulators) are currently in safety/tolerability trials or will begin such trials shortly. Many of the initial preclinical studies, however, did not examine the long-term effects of Htt lowering in aged models. Using a regulatable HD mouse model whose mHtt expression or total Htt expression are controlled via a Lac operator/repressor system, we found that global pre-symptomatic ~50% Htt lowering (starting prior to 3 months of age) of either mutant or total Htt expression was more beneficial in ameliorating HD mouse model phenotypes in comparison to later lowering (starting at 6 months of age or later), and that there were no obvious detrimental consequences from lowering total Htt expression in comparison to the allele-specific lowering of mHtt expression. However, we observed that in older mice, the beneficial effects of earlier Htt lowering were attenuated for some, but not all HD model phenotypes. We hypothesize that: (1) brain regions respond differentially to the amount and/or timing of mHtt lowering, and aging may exacerbate this effect, and (2) >50% reduction of mHtt expression may be needed to maintain homeostatic cellular and physiological functions whose efficiency declines with age. To test these hypotheses, and to provide a better understanding of how lowering mHtt expression affects homeostatic functions in older mice, we propose three aims. In (Aim 1), we will characterize the effects of globally lowering mHtt expression by ~75% using a different strain of Lac- regulatable HD mouse model to determine if the benefits of mHtt lowering can be extended beyond 12 months of age for all HD mouse model phenotypes. To determine if the DNA damage response and neuroimmflamation, two critical homeostatic functions that decline with age, can modulate the effect of mHtt lowering in older mice, we propose to characterize the DNA damage response in (Aim 2), while in (Aim 3), we propose to characterize activation of the inflammasome and measure meningeal lymphatic function in our mHtt-lowered mice and controls. Together, these aims should provide new insight into the degree of mHtt lowering that is needed to impact HD pathogenesis in aging mice. In addition, determining if two age-related pathways correlate with mHtt expression levels and/or HD model phenotypes could provide new potential therapeutic targets to be explored for the treatment of HD.

亨廷顿氏病（HD）是一种常染色体显性遗传的神经退行性疾病，其由以下原因引起： 在亨廷顿蛋白（HTT）内编码一段多聚谷氨酰胺（polyQ）的CAG三联体重复序列的扩增， HD基因的蛋白质产物。HD突变赋予有害的功能获得性，可能通过 毒性RNA转录物和蛋白质的表达，以及正常HTT功能的潜在丧失， 影响多种细胞功能正在开发许多降低HTT的策略-第三阶段 测试靶向总HTT表达或总HTT表达的反义寡核苷酸（ASO）的功效的临床试验， 选择性突变HTT（mHTT）表达正在进行中，而使用其他方法（miRNA）降低Htt 和剪接调节剂）目前正在进行安全性/耐受性试验或不久将开始这样的试验。许多 然而，最初的临床前研究没有检查在老年模型中Htt降低的长期效果。使用 可调节的HD小鼠模型，其mHtt表达或总Htt表达通过Lac 操纵子/阻遏物系统，我们发现，全球症状前~ 50%Htt降低（3个月前开始 无论是突变型Htt还是总Htt的表达， 与后来的降低（从6月龄或更晚开始）相比， 与等位基因特异性相比，降低总Htt表达的明显有害后果 降低mHtt表达。然而，我们观察到，在老年小鼠中，早期Htt的有益作用 降低对于一些但不是所有HD模型表型是减弱的。我们假设：（1）大脑区域 对mHtt降低的量和/或时间有不同的反应，衰老可能加剧这种影响， (2)可能需要>50%的mHtt表达降低以维持稳态的细胞和生理学特性。 效率随着年龄的增长而下降的功能。为了验证这些假设， 降低mHtt表达如何影响老年小鼠的稳态功能，我们提出了三个目标。在（目标 1），我们将表征使用不同的Lac菌株将mHtt表达整体降低约75%的效果。 可调节的HD小鼠模型，以确定mHtt降低的益处是否可延长至12个月以上 所有HD小鼠模型表型的年龄。为了确定DNA损伤反应和 神经炎症，两个随年龄增长而下降的关键稳态功能，可以调节mHtt的作用， 在老年小鼠中降低，我们建议在（目标2）中表征DNA损伤反应，而在（目标3）中，我们 建议在我们的研究中表征炎性小体的活化并测量脑膜淋巴功能， mHtt降低的小鼠和对照。总之，这些目标应该为mHtt的程度提供新的见解 降低影响衰老小鼠中HD发病机制所需的水平。此外，确定两个年龄相关的 与mHtt表达水平和/或HD模型表型相关的途径可以提供新的潜力 治疗HD的治疗靶点有待探索。