Identifying Parkinson’s disease penetrance-modifying factors in the population-based Cooperative Health Research in South Tyrol (CHRIS) cohort

帕金突变携带者的最大描述谱系（n=77）来自南蒂罗尔，包括许多帕金突变携带者的杂合子携带者，他们出现帕金森病（PD）的明显症状，而其他人可能有前驱症状或没有明显症状。我们的目标是剖析出改变这些变异的突变率的因素，使用南蒂罗尔合作健康研究（CHRIS）研究中的额外突变携带者（n= 13，490，来自同一地理区域）。在第一个资助期，测试影响线粒体功能的因素是否可以改变导致线粒体功能障碍的核突变的频率，我们观察到与未受影响的杂合子Parkin和PINK 1相比，受影响的杂合子Parkin和PINK 1的mtDNA突变负担增加。（磷酸酶和张力蛋白同源物诱导的推定激酶1）突变携带者和非携带者相比，这可能解释了表型（临床，亚临床）不一致，在这些个体具有相似的核遗传背景。然而，mtDNA变异的特异性作为一个突变标记物和增加mtDNA突变负荷的分子途径，最终导致神经退行性变，需要进一步研究更大的数据集。我们假设，将有一个突变PD基因和线粒体功能之间的相互作用，线粒体DNA突变负荷和/或拷贝数的影响，通过机制，涉及线粒体DNA的维护。在目标1中，我们将在CHRIS研究中确定额外的帕金突变携带者（预期总人数=650），并对他们的前驱或明显PD体征和症状进行表型表征。从一个成功的召回基因型试点研究中，我们已经建立了伦理框架，召回运营商进行更深入的表型和识别的表型，似乎能够区分运营商和非运营商在试点研究。使用深度线粒体测序，在目标2中，我们将确定目标1中鉴定的致病性帕金变异携带者血液中的mtDNA突变负荷和破坏性mtDNA变异。我们将测试这些变量是否影响疾病的表达率/表达率，并特别关注是否有可能检测预测亚临床或临床表型外观的突变负荷阈值。在目标3中，我们将在神经元细胞模型中测试帕金致病性变体、mtDNA突变和线粒体功能分子表型表达率之间的因果关系，并测试在存在此类帕金和mtDNA变体的情况下可能挽救线粒体功能的机制。我们将描述在不同时间点从参与者中提取的生物样本，以观察随时间的变化。这可能允许干预性研究测试神经保护策略（遗传或药理学），旨在在Parkin突变或其他影响线粒体功能的基因存在下使线粒体功能正常化。

The largest described pedigree of Parkin mutation carriers (n=77) originates from South Tyrol and includes numerous heterozygous carriers of Parkin mutation carriers who develop overt symptoms of Parkinson’s disease (PD), while others may have prodromal, or no obvious symptoms. We aim to dissect out the factors that modify the penetrance of these variants, using additional mutation carriers in the Cooperative Health Research in South Tyrol (CHRIS) study (n=13,490 from the same geographical region). In the first funding period, testing whether factors that influence mitochondrial function can alter penetrance of nuclear mutations causing mitochondrial dysfunction, we observed an increased burden of mtDNA mutations in affected vs. unaffected heterozygous Parkin and PINK1 (Phosphatase and tensin homolog-induced putative kinase 1) mutation carriers and compared to non-carriers, which might explain the phenotypic (clinical, sub-clinical) discordance in these individuals with similar nuclear genetic background. However, the specificity of mtDNA variation as a penetrance marker and the molecular pathways of increased mtDNA mutation load ultimately leading to neurodegeneration, require further investigation with larger datasets. We hypothesize that there will be a penetrance-modifying interaction between mutations in PD genes and mitochondrial function, influenced by both mtDNA mutation burden and/or copy number, through mechanisms that involve mtDNA maintenance. In Objective 1, we will identify additional Parkin mutation carriers (expected total n=650) in the CHRIS study and characterize them phenotypically for signs and symptoms of prodromal or overt PD. From a successful recall-by-genotype pilot study, we have established the ethics framework to recall carriers for deeper phenotyping and identified phenotypes that appear able to distinguish carriers and non-carriers in the pilot study. Using deep mitochondrial sequencing, in Objective 2, we will determine the mtDNA mutational load and damaging mtDNA variants in blood from carriers of pathogenic Parkin variants identified in Objective 1. We will test whether these variables influence disease penetrance/expressivity, and specifically look whether it is possible to detect a threshold of mutation burden that predicts sub-clinical or clinical phenotype appearance. In Objective 3, we will test the causal link between pathogenic variants in Parkin, mtDNA mutations and expressivity of molecular phenotypes of mitochondrial function in neuronal cell models, and test mechanisms that might rescue mitochondrial function in the presence of such Parkin and mtDNA variants. We will characterize biosamples drawn from participants at different time points to see changes over time. This might allow interventional studies to test neuroprotective strategies (genetic or pharmacological) aimed at normalizing mitochondrial function in the presence of Parkin mutations, or in other genes that influence mitochondrial function.