背景:脆性X综合征(FXS)是遗传性智力障碍的最常见形式,由CGG重复扩增(>200重复)引起。前突变等位基因(PM)(55-200CGG重复)与震颤共济失调综合征(FXTAS)相关,脆性X相关原发性卵巢功能不全(FXPOI),和自闭症问题。
目的:使用分子诊断方法筛选前突变携带者的频率,在一组怀疑有(FXS)临床特征的埃及男性中,检查是否存在前突变等位基因。
方法:目前的研究包括192名埃及男性儿童,92名参与者出现智力残疾,语言发育迟缓,自闭症样的特征,行为困难,焦虑,癫痫发作,与100名健康男性相比,抑郁症。所有病例均接受临床和神经影像学评估,以及使用甲基化特异性PCR(MS-PCR)和定量实时PCR(qRT-PCR)进行分子分析。
结果:在92个埃及男性(37%)CGG重复序列(55至200个)中,34个前突变携带者显示FMR1mRNA表达水平升高(p值<0.001)。此外,2个中间(IM)病例(0.03%)(45-55CGG重复)显示表达水平的不良增加(p值=0.02838)加上6个完全突变(FM)患者(0.07%)(>200CGG重复)(p值<0.001)导致FMR1基因沉默。
结论:包括(MS-PCR)和(qRT-PCR)在内的分子诊断试验被证明是检测前突变病例的一种灵敏而快速的筛查工具。此外,在前突变病例中,FMR1mRNA表达水平与CGG重复之间存在正相关,可以作为潜在的诊断标志物.建议将这些诊断工具应用于更多的临床疑似病例。
BACKGROUND: Fragile X syndrome (FXS) is the most common form of inherited intellectual disability, caused by CGG-repeats expansion (> 200 repeats). Premutation alleles (PM) (55-200 CGG repeats) are associated with tremor ataxia syndrome (FXTAS), fragile X-associated primary ovarian insufficiency (FXPOI), and autistic problems.
OBJECTIVE: To screen the frequency of premutation carriers using molecular diagnostic assays, in a cohort of Egyptian males with suspected clinical features of (FXS) checking for the presence of premutation alleles.
METHODS: The current study comprised 192 Egyptian male children, 92 participants presented with intellectual disability, delayed language development, autistic-like features, behavioral difficulties, anxiety, seizures, and depression compared to 100 healthy males. All cases were subjected to clinical and neuroimaging assessments, when indicated as well as molecular analysis using methylation-specific PCR (MS-PCR) and quantitative real-time PCR (qRT-PCR).
RESULTS: Thirty-four premutation carriers out of 92 Egyptian males (37%) of CGG repeats (55 to 200) were illustrated with elevated FMR1 mRNA expression level (p-value < 0.001). Additionally, 2 intermediate (IM) cases (0.03%) (45-55 CGG repeats) showed poor increase in expression level (p-value = 0.02838) plus 6 full mutation (FM) patients (0.07%) with (> 200 CGG repeats) (p-value < 0.001) resulted in FMR1 gene silence.
CONCLUSIONS: Molecular diagnostic assay including (MS-PCR) and (qRT-PCR) proved to be a sensitive and rapid screening tool for the detection of premutation cases. Furthermore, the presence of positive correlation between FMR1 mRNA expression levels with CGG repeats in premutation cases could serve as a potential diagnostic marker. Application of these diagnostic tools on larger number clinically suspected cases is recommended.