School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Monash University, Clayton, Victoria, 3800, Australia.
Centre for Molecular, Environmental, Genetic and Analytic Epidemiology, University of Melbourne Carlton, Victoria, 3053, Australia.
Sci Rep. 2016 Jul 8;6:29366. doi: 10.1038/srep29366.
Fragile X tremor ataxia syndrome (FXTAS) is a late-onset disorder manifesting in a proportion of FMR1 premutation individuals (PM: 55-199 CGG triplet expansions). FXTAS is associated with elevated levels of FMR1 mRNA which are toxic. In this study, relationships between neurocognitive and intra-step gait variability measures with mRNA levels, measured in blood samples, were examined in 35 PM and 35 matched control females. The real-time PCR assays measured FMR1 mRNA, and previously used internal control genes: β-Glucuronidase (GUS), Succinate Dehydrogenase 1 (SDHA) and Eukaryotic Translation Initiation Factor 4A (EI4A2). Although there was significant correlation of gait variability with FMR1 mRNA levels (p = 0.004) when normalized to GUS (FMR1/GUS), this was lost when FMR1 was normalized to SDHA and EI4A2 (2IC). In contrast, GUS mRNA level normalized to 2IC showed a strong correlation with gait variability measures (p < 0.007), working memory (p = 0.001) and verbal intelligence scores (p = 0.008). PM specific changes in GUS mRNA were not mediated by FMR1 mRNA. These results raise interest in the role of GUS in PM related disorders and emphasise the importance of using appropriate internal control genes, which have no significant association with PM phenotype, to normalize FMR1 mRNA levels.
脆性 X 震颤共济失调综合征（FXTAS）是一种晚发性疾病，在一部分 FMR1 前突变个体（PM：55-199 CGG 三核苷酸扩展）中表现出来。FXTAS 与 FMR1 mRNA 水平升高有关，而这些升高的 mRNA 是有毒的。在这项研究中，我们检查了 35 名 PM 和 35 名匹配对照女性的血液样本中神经认知和步内步态变异性测量值与 mRNA 水平之间的关系。实时 PCR 检测测量了 FMR1 mRNA，以及之前使用的内部对照基因：β-葡萄糖醛酸酶（GUS）、琥珀酸脱氢酶 1（SDHA）和真核翻译起始因子 4A（EI4A2）。尽管当 FMR1 与 GUS（FMR1/GUS）归一化时，步态变异性与 FMR1 mRNA 水平之间存在显著相关性（p=0.004），但当 FMR1 与 SDHA 和 EI4A2（2IC）归一化时，这种相关性就消失了。相比之下，与 2IC 归一化的 GUS mRNA 水平与步态变异性测量值（p<0.007）、工作记忆（p=0.001）和言语智力评分（p=0.008）之间存在很强的相关性。PM 特异性 GUS mRNA 变化不受 FMR1 mRNA 介导。这些结果引起了人们对 GUS 在 PM 相关疾病中的作用的兴趣，并强调了使用与 PM 表型没有显著关联的适当内部对照基因来归一化 FMR1 mRNA 水平的重要性。
