中国医学科学院基础医学研究所 & 北京协和医学院基础学院,北京 100730
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Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing 100730, China
DNA甲基化是重要的表观遗传现象,对基因表达发挥重要调控功能. 大量研究表明,基因DNA甲基化是重要的临床诊断生物标志物. 在临床上,实施快速、准确的DNA甲基化状态检测是诊断应用的前提和关键. 甲基化特异性PCR(methylation specific PCR,MSP)通过将两种引物与甲基化、非甲基化模板各自特异性结合和扩增,实现基因甲基化状态的区分,是切实可行、简单便捷的临床诊断实验技术. 但是,不同于常规PCR,MSP主要存在如何强化引物-甲基化/非甲基化模板特异性结合、降低引物序列Tm值差异、去除假阳性扩增及提高敏感性等四大难点. 尽管大多数MSP引物设计软件对上述难题都提出了各自解决办法,但在引物设计影响因素考虑、设计与评估并行处理及特异性扩增预测等方面仍然存在较大缺陷. 为此,本研究通过对MethPrimer、MSPPrimer、MethBlast、BiSearch等现有MSP引物设计软件原理的深入探究,以及对Bowtie、SAMtools和BEDTools等工具的有效综合整合,基于图形库Matplotlib和第三方Python功能库BioPython与Primer3-py实现了具有系列优点的甲基化特异性PCR引物设计与评估可视化工具MethyScan. 它具有引物设计、基因组索引、引物评估等三大完整功能模块,不仅可快速进行MSP引物设计,实现巢式(Nested)引物适配,还可基于4种基因组碱基转换模板分析引物结合信息,图形化展示非特异性扩增与目的片段差异,从而综合评估引物特异性-非特异性扩增. 同时,对食管癌、结直肠癌等多种恶性肿瘤中6个潜在生物标志物TFPI-2、NDRG4、CDKN2A、CD44、CASP8和SDHD的甲基化引物设计对比结果表明,MethyScan不仅可获得更多CpG位点的检测引物,而且所获得MSP引物位置与其他软件结果相同或相近,且引物间Tm值差值更小. 总之,作为首个图形化展示特异性-非特异性扩增差异MSP引物设计工具,MethyScan可有效提高甲基化引物设计准确性,为临床DNA甲基化检测项目开展、检测试验实施及诊断试剂盒研发提供有力支撑. MethyScan工具下载地址:
DNA methylation is an important epigenetic phenomena and plays crucial roles in the gene regulation. Many studies showed that DNA methylation can be used as clinical diagnostic biomarker. However, the ability to detect the DNA methylation status quickly and accurately is a prerequisite and key point for clinical application. By using two kinds of primers which can bind to methylated and unmethylated template respectively, methylation specific PCR (MSP) can distinguish DNA methylation status and prove to be a feasible and convenient diagnostic technique in clinical practice. Unlike traditional PCR, MSP mainly has four difficulties: how to enhance the specificity of binding to primer-methylated/unmethylated template, how to reduce the difference of Tm value of primer sequences, how to remove false positive amplification and how to improve sensitivity. Though most MSP primer design tools have proposed various solutions for those difficulties, there are still some defects in consideration of primer influencing factors, multitasking, prediction of specific amplification in MSP primer design and evaluation. Therefore, in this study, after deep exploration of existing MSP primer design tools, a novel MSP primer design and graphic evaluation tool named MethyScan was developed based on the integration of Bowtie, SAMtools, and BEDTools with Python graphic library Matplotlib and third-party functional libraries Biopython and Primer3-py. Three functional modules were involved in MethyScan including primer design, genome indexing and primer evaluation. MethyScan not only has the ability to perform MSP primers design and Nested primers adaptation, but also can evaluate primers specific/non-specific amplification with the analysis of primer binding information on four converted genomic templates and graphically displaying of the difference between non-specific amplification and target. Meanwhile, the comparison of MSP primer design for six potential biomarkers TFPI-2, NDRG4, CDKN2A, CD44, CASP8, and SDHD in esophageal cancer, colorectal cancer, and other malignant tumors suggested that MethyScan can not only obtain primers with more CpG sites, but also obtain primers with same or similar locations to those of other softwares, and the difference of Tm values of primers is even smaller. As the first MSP primer design tool for graphically displaying specific/non-specific amplification differences, MethyScan can effectively improve the accuracy of methylation primer design and provides strong support for the development of clinical DNA methylation detection projects, tests and diagnostic kits. The download address of MethyScan is:
曹英豪. MethyScan:一种甲基化特异性PCR引物设计及评估工具[J].生物化学与生物物理进展,2021,48(6):677-687
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