新一代测序技术的研究进展

大规模DNA测序技术是揭秘人类和其它生物遗传密码的重要技术,在分子生物学和基础医学领域有广泛应用。第二代测序技术的出现使DNA测序的通量大幅提高,测序的成本大幅下降,原来只有在大型测序中心才能完成的测序任务现在已经可以在更多的实验室展开。但是,早期的第二代测序技术仍然存在诸如文库构建过程复杂、测序成本依然较高等缺点。为了克服上述缺点,近三年发展了几种新的第二代和第三代测序技术,这些技术不仅继承了早期第二代测序技术通量高的优点,而且在文库构建等方面取得了重要突破,进一步简化了测序操作,降低了测序成本,缩短了测序时间。本文就几种最新的大规模测序技术的原理、特点与发展趋势进行简要介绍。     

新一代测序技术应用于microRNA检测

MicroRNAs(miRNAs)是一类在进化上高度保守的非编码小分子单链RNA(~22nt),在基因转录后调控中发挥至关重要的作用。越来越多的证据表明,miRNAs参与很多重要的生理和病理过程,例如发育、器官形成、调亡、细胞增殖、肿瘤发生等。近年来飞速发展的新一代测序技术在miRNA检测方面具有重要的应用。文章简要介绍了新一代测序技术3大平台的基本步骤和原理,测序数据的生物信息学分析方法以及新一代测序技术在miRNA方向的主要应用。相比于传统的miRNA检测方法,新一代测序技术具有通量高、对遗传物质检测完全且准确度高,可重复性好等优点,在探索新miRNA、miRNA互补链、miRNA编辑、miRNA异构体检测以及miRNA靶基因检测等方面具有巨大优势。随着新一代测序技术的不断发展,测序成本不断降低,在未来几年,新一代测序技术的使用率或将大大增加。新一代测序技术的不断应用将进一步促进人类对于miRNA在各种生理病理过程中的功能和调控的认识。     

MELAS和MERRF综合征相关mtDNA突变位点检测集成芯片的建立

摘要: 文中建立了一种新型的寡核苷酸芯片, 用于线粒体脑肌病伴高乳酸血症和卒中样发作(Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes, MELAS)和肌阵挛性癫痫伴发不规整红纤维(Myoclonic epilepsy with ragged red fibers, MERRF)线粒体DNA所有已知突变位点的集成检测。将31对allele位点特异性的寡核苷酸探针包被在醛基修饰的载玻片表面, 以多重不对称PCR方法制备Cy5荧光标记靶基因。利用此芯片对5例MELAS患者、5例MERRF患者及20例健康对照进行筛查, 结果发现, MELAS患者均为MT-T1基因A3243G突变; 在MERRF患者组, MT-TK基因A8344G突变4例, T8356C突变1例; 健康对照组均未发现31种相关mtDNA突变。芯片检测与DNA测序结果完全一致。结果表明, 这种寡核苷酸芯片可以对MELAS和MERRF综合征已知突变位点进行同步快速检测, 具有较高的灵敏度和特异性。这一模式的基因芯片经过适当改装后也可用于其他人类线粒体疾病的基因诊断。     

DNA测序技术概述

DNA测序技术作为现代生命科学研究的核心技术之一,自上世纪70年代中期DNA发明以来发展迅速。我们简要综述现有的几代DNA测序技术的原理及其发展历程,并对未来可能出现的第三代测序进行预测。     

新一代测序技术在植物转录组研究中的应用

随着DNA测序技术的发展,新一代测序技术以其高通量、低成本的特点,成为越来越多的生物学研究者在开展工作时的首选。在所有的新一代测序技术中,454测序系统是最早实现商业化且发展相对成熟的一种,目前被广泛的应用于各个领域的生物学研究中。文章以454测序系统为例,综述了新一代测序系统的原理、优缺点,及其在植物转录组研究中的应用,并对其在植物研究领域中可能的发展应用方向进行了展望。     

古DNA单链测序文库的建立与检测北大核心CSCD

2005年问世的第二代测序技术在古DNA领域的应用,突破了第一代测序技术在绝灭或死亡生物全基因组获取手段上的局限。借助古基因组信息,研究者能够从更为系统的实时分子证据角度,解读诸如人类起源、大型绝灭哺乳动物迁移演化、动植物家养驯化以及早期人类社会生活模式等古生物学、遗传学与演化生物学问题。引入第二代测序技术之后,传统的古DNA研究方法及流程得以改变,剔除了原有的实验流程中耗时的分子克隆步骤,引入了与第二代测序技术紧密相关的古DNA单链测序文库构建环节。古DNA单链测序文库的构建,是将古DNA双链模板变性成单链后,通过向单链古DNA两端添加人工DNA片段,将古DNA分子转变成能被测序仪识别的文库分子。针对古DNA分子微量、高度片段化以及普遍存在碱基损伤的特点,古DNA单链测序文库,能够高效获取古DNA材料中的遗传信息。本文系统介绍古DNA单链测序文库建立流程,以及对文库质量进行检测的方法,为研究者运用第二代测序技术测定绝灭或死亡生物全基因组提供方法借鉴。     

新一代测序的拷贝数变异检测算法研究与设计

基于不同的测序技术,基因拷贝数变异的检测方法有多种,但时间复杂度较高,而新一代测序技术的发展为基因拷贝数变异检测的研究开辟了新领域。通过仿真实验、置换检验设计出一种新的基于新一代测序的拷贝数变异检测算法。不同于其它算法,本算法无需参考样本,通过直接研究比对后的序列以及reads与拷贝数的关系,来研究检测拷贝数变异,实验结果表明在时间复杂度上能提高50%以上的运算速度,这对今后拷贝数与疾病的研究具有重要意义。     

新一代测序技术及其产业化前景

新一代测序技术是近几年建立的一种新型超高通量技术,是DNA测序技术的一次革命。具有测序通量高、速度快、成本低等特点。新一代测序技术出现后的短短几年时间,已被广泛应用于生命科学基础研究,在临床诊疗等许多领域也显示出巨大的应用潜力,对整个生物技术产业的发展将产生积极、深远的影响。本文简要介绍了目前比较成熟的新一代测序技术平台的原理、特点和基本实验流程,总结了新一代测序技术在生命科学研究中的应用,展望了今后的产业化前景。     

DNA测序技术的发展历史与最新进展

DNA测序技术是现代分子生物学研究中最常用的技术。从1977年第一代测序技术的出现,经过30多年的发展,DNA测序技术取得重大进展,以高通量为特点的第二代测序技术逐步成熟并商业化,以单分子测序为特点的第三代测序技术也已经出现。介绍每一代测序技术的特点,并重点介绍了第二代测序技术及其应用。展望新的测序技术对于未来生物学研究及人们自身健康与人类疾病等方面研究的影响。     

DNA测序技术比较

自从1953年,J.D.Watson和F.H.C.Crick发现DNA的双螺旋模型之后,DNA测序技术随着科学的进步得到了迅猛发展.1977年Sanger[1]发明DNA双脱氧末端终止测序技术,Maxam与Gilbert[2]发明利用化学降解法进行测序的技术,2种测序技术被誉为DNA测序技术的始祖.随后,在第1代DNA测序技术的基础上,相继出现了第2代测序技术、基因芯片技术以及第3代测序技术.总结并展望了每一代测序技术及基因芯片技术的诞生、原理及应用前景,为利用测序技术研究基因表达提供理论基础和实验依据.     

Detecting Large Germline Rearrangements of BRCA1 by Next Generation Tumor Sequencing

Molecular Biology - A majority of BRCA1/2 (BRCA) pathogenic variants (PVs) are single nucleotide substitutions or small insertions/deletions. Copy number variations (CNVs), also known as large...     

A Pathogenic Mosaic TP53 Mutation in Two Germ Layers Detected by Next Generation Sequencing

Background

Li-Fraumeni syndrome is caused by germline TP53 mutations and is clinically characterized by a predisposition to a range of cancers, most commonly sarcoma, brain tumours and leukemia. Pathogenic mosaic TP53 mutations have only rarely been described.

Methods and Findings

We describe a 2 years old child presenting with three separate cancers over a 6 month period; two soft tissue mesenchymal tumors and an aggressive metastatic neuroblastoma. As conventional testing of blood DNA by Sanger sequencing for mutations in TP53, ALK, and SDH was negative, whole exome sequencing of the blood DNA of the patient and both parents was performed to screen more widely for cancer predisposing mutations. In the patient''s but not the parents'' DNA we found a c.743 G>A, p.Arg248Gln (CCDS11118.1) TP53 mutation in 3–20% of sequencing reads, a level that would not generally be detectable by Sanger sequencing. Homozygosity for this mutation was detected in all tumor samples analyzed, and germline mosaicism was demonstrated by analysis of the child''s newborn blood spot DNA. The occurrence of separate tumors derived from different germ layers suggests that this de novo mutation occurred early in embryogenesis, prior to gastrulation.

Conclusion

The case demonstrates pathogenic mosaicim, detected by next generation deep sequencing, that arose in the early stages of embryogenesis.     

Collection and Extraction of Saliva DNA for Next Generation Sequencing

The preferred source of DNA in human genetics research is blood, or cell lines derived from blood, as these sources yield large quantities of high quality DNA. However, DNA extraction from saliva can yield high quality DNA with little to no degradation/fragmentation that is suitable for a variety of DNA assays without the expense of a phlebotomist and can even be acquired through the mail. However, at present, no saliva DNA collection/extraction protocols for next generation sequencing have been presented in the literature. This protocol optimizes parameters of saliva collection/storage and DNA extraction to be of sufficient quality and quantity for DNA assays with the highest standards, including microarray genotyping and next generation sequencing.     

DNA Qualification Workflow for Next Generation Sequencing of Histopathological Samples

Histopathological samples are a treasure-trove of DNA for clinical research. However, the quality of DNA can vary depending on the source or extraction method applied. Thus a standardized and cost-effective workflow for the qualification of DNA preparations is essential to guarantee interlaboratory reproducible results. The qualification process consists of the quantification of double strand DNA (dsDNA) and the assessment of its suitability for downstream applications, such as high-throughput next-generation sequencing. We tested the two most frequently used instrumentations to define their role in this process: NanoDrop, based on UV spectroscopy, and Qubit 2.0, which uses fluorochromes specifically binding dsDNA. Quantitative PCR (qPCR) was used as the reference technique as it simultaneously assesses DNA concentration and suitability for PCR amplification. We used 17 genomic DNAs from 6 fresh-frozen (FF) tissues, 6 formalin-fixed paraffin-embedded (FFPE) tissues, 3 cell lines, and 2 commercial preparations. Intra- and inter-operator variability was negligible, and intra-methodology variability was minimal, while consistent inter-methodology divergences were observed. In fact, NanoDrop measured DNA concentrations higher than Qubit and its consistency with dsDNA quantification by qPCR was limited to high molecular weight DNA from FF samples and cell lines, where total DNA and dsDNA quantity virtually coincide. In partially degraded DNA from FFPE samples, only Qubit proved highly reproducible and consistent with qPCR measurements. Multiplex PCR amplifying 191 regions of 46 cancer-related genes was designated the downstream application, using 40 ng dsDNA from FFPE samples calculated by Qubit. All but one sample produced amplicon libraries suitable for next-generation sequencing. NanoDrop UV-spectrum verified contamination of the unsuccessful sample. In conclusion, as qPCR has high costs and is labor intensive, an alternative effective standard workflow for qualification of DNA preparations should include the sequential combination of NanoDrop and Qubit to assess the purity and quantity of dsDNA, respectively.     

第二代测序在检测人类基因突变中的应用

很多的人类疾病与基因突变有关,基因突变在疾病的诊断和治疗中起到了至关重要的作用.第二代高通量测序,其特点为通量高、速度快、成本低,给检测基因突变带来了革命性的变化.该技术检测基因突变的流程简单,研究人员运用全基因组从测序,目标基因组测序以及转录组测序能够实现基因突变的全方位、高准确的检测.     

A Universal Method for Species Identification of Mammals Utilizing Next Generation Sequencing for the Analysis of DNA Mixtures

Species identification can be interesting in a wide range of areas, for example, in forensic applications, food monitoring and in archeology. The vast majority of existing DNA typing methods developed for species determination, mainly focuses on a single species source. There are, however, many instances where all species from mixed sources need to be determined, even when the species in minority constitutes less than 1 % of the sample. The introduction of next generation sequencing opens new possibilities for such challenging samples. In this study we present a universal deep sequencing method using 454 GS Junior sequencing of a target on the mitochondrial gene 16S rRNA. The method was designed through phylogenetic analyses of DNA reference sequences from more than 300 mammal species. Experiments were performed on artificial species-species mixture samples in order to verify the method’s robustness and its ability to detect all species within a mixture. The method was also tested on samples from authentic forensic casework. The results showed to be promising, discriminating over 99.9 % of mammal species and the ability to detect multiple donors within a mixture and also to detect minor components as low as 1 % of a mixed sample.     

DNA提取对微生物多样性测序分析的影响

运用高通量测序技术分析复杂样品中微生物种群的变化情况,已经成为目前微生物研究领域的热点问题之一。而微生物的样品准备,如DNA提取和16S可变区的扩增等,对于测序完成后的数据分析以及微生物原始群落组成的影响是至关重要的。采用国产试剂盒(天根土壤微生物基因组提取试剂盒)和进口试剂盒(MOBIO土壤微生物基因组提取试剂盒)分别对土壤样品和羊瘤胃食糜样品进行DNA提取。然后选取总DNA起始量为25ng,对16S V3可变区进行PCR扩增和文库构建,最后通过数据分析比较不同试剂盒提取的DNA对微生物多样性变化的影响,包括OTU数目、稀释曲线、微生物数量及物种种类等。研究发现,在相同DNA模板量和PCR条件下,进口试剂盒提取的DNA能够获得更多的微生物种类。     

线粒体DNA突变与肿瘤发生

线粒体是哺乳动物细胞内唯一含有核外遗传物质的细胞器。由于其自身的特征以及所处的环境等因素,较之于nDNA,mtDNA更容易受到损伤因子的攻击。mtDNA突变,mtDNA片段整合入核基因组等可能与肿瘤的发生以及肿瘤表型的产生有较为密切的关系。深入研究线粒体及其基因组的结构和表达调控,探讨核质关系,对于阐明细胞癌变的机制可能具有重要意义。     

Mutation Detection in Patients with Retinal Dystrophies Using Targeted Next Generation Sequencing

Retinal dystrophies (RD) constitute a group of blinding diseases that are characterized by clinical variability and pronounced genetic heterogeneity. The different nonsyndromic and syndromic forms of RD can be attributed to mutations in more than 200 genes. Consequently, next generation sequencing (NGS) technologies are among the most promising approaches to identify mutations in RD. We screened a large cohort of patients comprising 89 independent cases and families with various subforms of RD applying different NGS platforms. While mutation screening in 50 cases was performed using a RD gene capture panel, 47 cases were analyzed using whole exome sequencing. One family was analyzed using whole genome sequencing. A detection rate of 61% was achieved including mutations in 34 known and two novel RD genes. A total of 69 distinct mutations were identified, including 39 novel mutations. Notably, genetic findings in several families were not consistent with the initial clinical diagnosis. Clinical reassessment resulted in refinement of the clinical diagnosis in some of these families and confirmed the broad clinical spectrum associated with mutations in RD genes.     

Short Barcodes for Next Generation Sequencing

We consider the design and evaluation of short barcodes, with a length between six and eight nucleotides, used for parallel sequencing on platforms where substitution errors dominate. Such codes should have not only good error correction properties but also the code words should fulfil certain biological constraints (experimental parameters). We compare published barcodes with codes obtained by two new constructions methods, one based on the currently best known linear codes and a simple randomized construction method. The evaluation done is with respect to the error correction capabilities, barcode size and their experimental parameters and fundamental bounds on the code size and their distance properties. We provide a list of codes for lengths between six and eight nucleotides, where for length eight, two substitution errors can be corrected. In fact, no code with larger minimum distance can exist.