Faculdade de Ciências e Tecnologia, Universidade dos Açores (UAc), Ponta Delgada, Portugal.
Instituto de Investigação e Inovação em Saúde (I3S), Universidade do Porto, Porto, Portugal.
Mol Neurobiol. 2019 Jan;56(1):119-124. doi: 10.1007/s12035-018-1069-x. Epub 2018 Apr 21.
Molecular alterations reflecting pathophysiologic changes thought to occur many years before the clinical onset of Machado-Joseph disease (MJD)/spinocerebellar ataxia type 3 (SCA3), a late-onset polyglutamine disorder, remain unidentified. The absence of molecular biomarkers hampers clinical trials, which lack sensitive measures of disease progression, preventing the identification of events occurring prior to clinical onset. Our aim was to analyse the mtDNA content and the amount of the common deletion (m.8482_13460del4977) in a cohort of 16 preataxic MJD mutation carriers, 85 MJD patients and 101 apparently healthy age-matched controls. Relative expression levels of RPPH1, MT-ND1 and MT-ND4 genes were assessed by quantitative real-time PCR. The mtDNA content was calculated as the difference between the expression levels of a mitochondrial gene (MT-ND1) and a nuclear gene (RPPH1); the amount of mtDNA common deletion was calculated as the difference between expression levels of a deleted (MT-ND4) and an undeleted (MT-ND1) mitochondrial genes. mtDNA content in MJD carriers was similar to that of healthy age-matched controls, whereas the percentage of the common deletion was significantly increased in MJD subjects, and more pronounced in the preclinical stage (p < 0.05). The BCL2/BAX ratio was decreased in preataxic carriers compared to controls, suggesting that the mitochondrial-mediated apoptotic pathway is altered in MJD. Our findings demonstrate for the first time that accumulation of common deletion starts in the preclinical stage. Such early alterations provide support to the current understanding that any therapeutic intervention in MJD should start before the overt clinical phenotype.
反映 Machado-Joseph 病（MJD）/脊髓小脑共济失调 3 型（SCA3）发病前多年生理病理变化的分子改变仍然未知。MJD/SCA3 是一种迟发性多聚谷氨酰胺疾病，缺乏分子生物标志物，这阻碍了临床试验的开展，因为这些临床试验缺乏疾病进展的敏感衡量标准，从而无法识别发病前的事件。我们的目的是分析一组 16 名预发病 MJD 突变携带者、85 名 MJD 患者和 101 名年龄匹配的健康对照者的 mtDNA 含量和常见缺失（m.8482_13460del4977）的量。通过实时定量 PCR 评估 RPPH1、MT-ND1 和 MT-ND4 基因的相对表达水平。mtDNA 含量通过线粒体基因（MT-ND1）和核基因（RPPH1）表达水平之间的差异计算得出；mtDNA 常见缺失的量通过缺失（MT-ND4）和未缺失（MT-ND1）线粒体基因的表达水平之间的差异计算得出。MJD 携带者的 mtDNA 含量与健康年龄匹配的对照组相似，而 MJD 患者的 mtDNA 常见缺失百分比显著增加，且在临床前期更为明显（p<0.05）。与对照组相比，预发病携带者的 BCL2/BAX 比值降低，提示 MJD 中线粒体介导的凋亡途径发生改变。我们的研究结果首次表明，常见缺失的积累始于临床前阶段。这些早期改变为当前的理解提供了支持，即 MJD 中的任何治疗干预都应在明显的临床表型出现之前开始。
