V krátkém přehledu je pojednáno o základních metodách čtení pořadí jednotlivých bází v molekule DNA. Podrobněji je popsáno tzv. Sangerovo sekvenování, které je v současnosti zdaleka nejrozšířenější klasickou metodou. Detailně je osvětlen princip určení pořadí bází pomocí tvorby fragmentů se známou koncovou bází prostřednictvím terminační syntézy DNA a možnosti separace a detekce získaných produktů. Krátce jsou též zmíněny některé alternativní metodiky. Dále je vysvětlen postup při analýze získaných sekvenačních dat, možné výstupy z těchto dat a také omezení a možná úskalí Sangerovy sekvenační analýzy.
In this article the basic methods of reading nucleotide sequences in DNA molecules are summarized. Sanger sequencing is described most thoroughly as it is the most frequent routine method currently being utilized. The article describes in detail the principle of sequence determination through the production of fragments with a known end base using chain termination synthesis of DNA and ways of separation and detection of the fragments. Some alternative methods of sequencing are mentioned in short. Basic approaches of analyzing sequence data are explained as well as different outcomes, obstacles and challenges.
- Keywords
- Sanger, sekvenogram, kapilární elektroforéza, ddNTP, syntéza,
- MeSH
- Diagnostic Errors MeSH
- Dideoxynucleotides MeSH
- DNA genetics MeSH
- Electrophoresis, Capillary MeSH
- Fluorescence MeSH
- Humans MeSH
- Mutation genetics MeSH
- Sequence Analysis, DNA * methods MeSH
- Check Tag
- Humans MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
- Review MeSH
Metagenomic high-throughput sequencing (mHTS) is a hypothesis-free, universal pathogen detection technique for determination of the DNA/RNA sequences in a variety of sample types and infectious syndromes. mHTS is still in its early stages of translating into clinical application. To support the development, implementation and standardization of mHTS procedures for virus diagnostics, the European Society for Clinical Virology (ESCV) Network on Next-Generation Sequencing (ENNGS) has been established. The aim of ENNGS is to bring together professionals involved in mHTS for viral diagnostics to share methodologies and experiences, and to develop application recommendations. This manuscript aims to provide practical recommendations for the wet lab procedures necessary for implementation of mHTS for virus diagnostics and to give recommendations for development and validation of laboratory methods, including mHTS quality assurance, control and quality assessment protocols.
- MeSH
- Metagenomics * MeSH
- Viruses * genetics MeSH
- High-Throughput Nucleotide Sequencing MeSH
- Publication type
- Journal Article MeSH
Predoperačná cytopatologická diagnostika nádorov pankreatobiliárneho traktu je senzitívne a špecifické vyšetrenie, ktoré má nezastupiteľnú úlohu v manažmente týchto ochorení. Patológ by sa mal vždy pokúsiť stanoviť čo najpresnejšiu diagnózu a minimalizovať počet nejednoznačných diagnóz („atypické bunky“), ktoré spôsobujú v ďalšom manažmente dilemu. Diagnostická presnosť cytopatológie môže byť výrazne zlepšená rozumným použitím imunohistochémie a metód molekulovej genetiky. Najnovším diagnostickým nástrojom v pankreatobiliárnej cytopatológii je masívne paralelné sekvenovanie (next generation sequencing/NGS). NGS je robustná diagnostická metóda, ktorá navyše prináša informácie o prognóze a informácie potenciálne využiteľné pri výbere cielenej liečby.
Preoperative cytopathology of pancreatobiliary neoplastic lesions is a sensitive and specific method and is irreplaceable in the diagnosis and clinical management of these diseases. Pathologists should make every attempt to provide diagnosis as precise as possible and minimize the rate of “atypical” results, which create management dilemmas. The diagnostic accuracy of cytopathology can be significantly improved by judicious use of ancillary studies, including immunohistochemistry and molecular genetics. Next generation sequencing (NGS) is the latest addition to pancreatobiliary cytopathology diagnostic arsenal. NGS is not only a very robust diagnostic tool, but also carries significant prognostic and therapeutic information.
Recent developments in high-throughput sequencing (HTS), also called next-generation sequencing (NGS), technologies and bioinformatics have drastically changed research on viral pathogens and spurred growing interest in the field of virus diagnostics. However, the reliability of HTS-based virus detection protocols must be evaluated before adopting them for diagnostics. Many different bioinformatics algorithms aimed at detecting viruses in HTS data have been reported but little attention has been paid thus far to their sensitivity and reliability for diagnostic purposes. Therefore, we compared the ability of 21 plant virology laboratories, each employing a different bioinformatics pipeline, to detect 12 plant viruses through a double-blind large-scale performance test using 10 datasets of 21- to 24-nucleotide small RNA (sRNA) sequences from three different infected plants. The sensitivity of virus detection ranged between 35 and 100% among participants, with a marked negative effect when sequence depth decreased. The false-positive detection rate was very low and mainly related to the identification of host genome-integrated viral sequences or misinterpretation of the results. Reproducibility was high (91.6%). This work revealed the key influence of bioinformatics strategies for the sensitive detection of viruses in HTS sRNA datasets and, more specifically (i) the difficulty in detecting viral agents when they are novel or their sRNA abundance is low, (ii) the influence of key parameters at both assembly and annotation steps, (iii) the importance of completeness of reference sequence databases, and (iv) the significant level of scientific expertise needed when interpreting pipeline results. Overall, this work underlines key parameters and proposes recommendations for reliable sRNA-based detection of known and unknown viruses.
PURPOSE: Preimplantation genetic testing for monogenic disorders (PGT-M) allows early diagnosis in embryos conceived in vitro. PGT-M helps to prevent known genetic disorders in affected families and ensures that pathogenic variants in the male or female partner are not passed on to offspring. The trend in genetic testing of embryos is to provide a comprehensive platform that enables robust and reliable testing for the causal pathogenic variant(s), as well as chromosomal abnormalities that commonly occur in embryos. In this study, we describe PGT protocol that allows direct mutation testing, haplotyping, and aneuploidy screening. METHODS: Described PGT protocol called OneGene PGT allows direct mutation testing, haplotyping, and aneuploidy screening using next-generation sequencing (NGS). Whole genome amplification product is combined with multiplex PCR used for SNP enrichment. Dedicated bioinformatic tool enables mapping, genotype calling, and haplotyping of informative SNP markers. A commercial software was used for aneuploidy calling. RESULTS: OneGenePGT has been implemented for seven of the most common monogenic disorders, representing approximately 30% of all PGT-M indications at our IVF centre. The technique has been thoroughly validated, focusing on direct pathogenic variant testing, haplotype identification, and chromosome abnormality detection. Validation results show full concordance with Sanger sequencing and karyomapping, which were used as reference methods. CONCLUSION: OneGene PGT is a comprehensive, robust, and cost-effective method that can be established for any gene of interest. The technique is particularly suitable for common monogenic diseases, which can be performed based on a universal laboratory protocol without the need for set-up or pre-testing.
- MeSH
- Aneuploidy MeSH
- Blastocyst pathology MeSH
- Genetic Testing methods MeSH
- Humans MeSH
- Mutation genetics MeSH
- Preimplantation Diagnosis * methods MeSH
- Pregnancy MeSH
- High-Throughput Nucleotide Sequencing methods MeSH
- Check Tag
- Humans MeSH
- Male MeSH
- Pregnancy MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
Východiska: Mozkové metastázy (BM) jsou nejčastějšími intrakraniálními nádory u dospělých onkologických pacientů. Zatímco dříve byly BM léčeny pouze symptomaticky, přístup k terapii se mění v důsledku zvyšující se incidence, vyplývající z efektivnější léčby primárních nádorů a časnějšího záchytu malých asymptomatických BM. Protože prognóza pacientů s BM je vysoce variabilní, bylo by užitečné zlepšit diagnostické a prognostické nástroje začleněním nových výkonných biomarkerů. MikroRNA (miRNA) jsou v tomto ohledu slibné a díky své vysoké stabilitě vhodné jak pro sekvenování (RNA-Seq), tak pro retrospektivní analýzy v tkáních fixovaných formalinem a zalitých v parafinu (formalin-fixed and paraffin embedded – FFPE). Materiál a metody: Celková RNA obohacená o miRNA byla izolována ze 71 čerstvě zmrazených histopatologicky potvrzených tkání BM s původem v pěti typech nádorů (karcinom plic, 37 %; melanom, 23 %; karcinom prsu, 18 %; renální karcinom, 15 %; kolorektální karcinom, 7 %). Před léčbou byl od každého pacienta získán informovaný souhlas schválený místní etickou komisí. Z RNA byly připraveny knihovny pro sekvenování na platformě NextSeq 500 (Illumina). Mapování čtení na referenci bylo provedeno pomocí nástroje miraligner a databáze miRBase a diferenciální analýza pro 2 437 maturovaných miRNA pomocí nástroje limma. Molekuly miRNA ze vzorků celkové RNA izolovaných z retrospektivního souboru 119 FFPE tkání byly reverzně transkribovány a exprese vybraných diferenciálně exprimovaných miRNA (miR-122-5p, miR-141-3p, miR-146a-5p, miR-194-5p, miR-200c-3p, miR-211-3p, miR-215-5p, miR-514b-3p, miR-934, miR-1270) byla validována pomocí qPCR. Výsledky: Diferenciální analýzou bylo identifikováno 373 miRNA s významně odlišnou expresí mezi pěti skupinami BM (p < 0,001). Následnou validací byla ověřena významně odlišná exprese vybraných miRNA v pěti skupinách BM. Závěr: Prezentované výsledky potvrzují důležitost studia dysregulované exprese miRNA v BM a diagnostický potenciál validovaných miRNA.
Background: Brain metastases (BM) are the most common intracranial tumors in adult cancer patients. While previously BMs were only treated symptomatically, the approach to therapy is changing due to the increasing incidence resulting from more effective treatment of primary tumors and earlier detection of small asymptomatic BMs. As the prognosis of patients with BM is highly variable, it would be useful to improve diagnostic and prognostic tools by incorporating new powerful biomarkers. MicroRNAs (miRNAs) are promising in this regard and, due to their high stability, suitable both for sequencing (RNA-Seq) and for retrospective analyses in formalin-fixed and paraffin-embedded (FFPE) tissues. Material and methods: Total RNA enriched for miRNAs was isolated from 71 fresh-frozen histopathologically confirmed BM tissues originating from 5 tumor types (lung cancer, 37%; melanoma, 23%; breast cancer, 18%; renal cell carcinoma, 15%; colorectal carcinoma, 7%). Informed consent approved by the local ethics committee was obtained from each patient before treatment. Libraries were prepared from RNA for sequencing on the NextSeq 500 platform (Illumina). Read-to-reference mapping was performed using the tool miraligner and the database miRBase, and differential analysis for 2 437 matured miRNAs was done using the tool limma. MiRNA molecules from total RNA samples isolated from a retrospective set of 119 FFPE tissues were reverse transcribed and the expression of selected differentially expressed miRNAs (miR-122-5p, miR-141-3p, miR-146a-5p, miR-194-5p, miR-200c -3p, miR-211-3p, miR-215-5p, miR-514b-3p, miR-934, miR-1270) was validated by qPCR. Results: Differential analysis identified 373 miRNAs with significantly different expression between the five BM groups (P < 0.001). Subsequent pilot validation verified significantly different expression of selected miRNAs in five BM groups. Conclusion: The presented results confirm the importance of studying dysregulated miRNA expression in BM and the diagnostic potential of validated miRNAs.
Working with mitochondrial DNA from highly degraded samples is challenging. We present a whole mitogenome Illumina-based sequencing method suitable for highly degraded samples. The method makes use of double-stranded library preparation with hybridization-based target enrichment. The aim of the study was to implement a new user-friendly method for analysing many ancient DNA samples at low cost. The method combines the Swift 2S™ Turbo library preparation kit and xGen® panel for mitogenome enrichment. Swift allows to use low input of aDNA and own adapters and primers, handles inhibitors well, and has only two purification steps. xGen is straightforward to use and is able to leverage already pooled libraries. Given the ancient DNA is more challenging to work with, the protocol was developed with several improvements, especially multiplying DNA input in case of low concentration DNA extractions followed by AMPure® beads size selection and real-time pre-capture PCR monitoring in order to avoid cycle-optimization step. Nine out of eleven analysed samples successfully retrieved mitogenomes. Hence, our method provides an effective analysis of whole mtDNA, and has proven to be fast, cost-effective, straightforward, with utilisation in population-wide research of burial sites.
A robust and widely applicable method for sampling of aquatic microbial biofilm and further sample processing is presented. The method is based on next-generation sequencing of V4-V5 variable regions of 16S rRNA gene and further statistical analysis of sequencing data, which could be useful not only to investigate taxonomic composition of biofilm bacterial consortia but also to assess aquatic ecosystem health. Five artificial materials commonly used for biofilm growth (glass, stainless steel, aluminum, polypropylene, polyethylene) were tested to determine the one giving most robust and reproducible results. The effect of used sampler material on total microbial composition was not statistically significant; however, the non-plastic materials (glass, metal) gave more stable outputs without irregularities among sample parallels. The bias of the method is assessed with respect to the employment of a non-quantitative step (PCR amplification) to obtain quantitative results (relative abundance of identified taxa). This aspect is often overlooked in ecological and medical studies. We document that sequencing of a mixture of three merged primary PCR reactions for each sample and further evaluation of median values from three technical replicates for each sample enables to overcome this bias and gives robust and repeatable results well distinguishing among sampling localities and seasons.
- MeSH
- Bacteria classification genetics MeSH
- Biofilms * growth & development MeSH
- Water Microbiology * MeSH
- Microbiota genetics MeSH
- Environmental Monitoring methods MeSH
- Specimen Handling MeSH
- Reproducibility of Results MeSH
- RNA, Ribosomal, 16S genetics MeSH
- Sequence Analysis, DNA * MeSH
- High-Throughput Nucleotide Sequencing * MeSH
- Publication type
- Journal Article MeSH
- Comparative Study MeSH
Marine oomycetes have recently been shown to be concurrently infected by (-)ssRNA viruses of the order Bunyavirales. In this work, even higher virus variability was found in a single isolate of Phytophthora condilina, a recently described member of Phytophthora phylogenetic Clade 6a, which was isolated from brackish estuarine waters in southern Portugal. Using total and small RNA-seq the full RdRp of 13 different potential novel bunya-like viruses and two complete toti-like viruses were detected. All these viruses were successfully confirmed by reverse transcription polymerase chain reaction (RT-PCR) using total RNA as template, but complementarily one of the toti-like and five of the bunya-like viruses were confirmed when dsRNA was purified for RT-PCR. In our study, total RNA-seq was by far more efficient for de novo assembling of the virus sequencing but small RNA-seq showed higher read numbers for most viruses. Two main populations of small RNAs (21 nts and 25 nts-long) were identified, which were in accordance with other Phytophthora species. To the best of our knowledge, this is the first study using small RNA sequencing to identify viruses in Phytophthora spp.
- MeSH
- Phylogeny MeSH
- Genome, Viral MeSH
- RNA, Small Untranslated genetics MeSH
- Open Reading Frames MeSH
- Phytophthora virology MeSH
- RNA, Viral genetics MeSH
- RNA Viruses classification genetics isolation & purification MeSH
- Sequence Analysis, DNA MeSH
- Sequence Analysis, RNA * MeSH
- RNA-Seq MeSH
- Virus Diseases virology MeSH
- Computational Biology MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Geographicals
- Portugal MeSH
PURPOSE: A new high-resolution next-generation sequencing (NGS)-based method was established to type closely related European type II Toxoplasma gondii strains. METHODS: T. gondii field isolates were collected from different parts of Europe and assessed by whole genome sequencing (WGS). In comparison to ME49 (a type II reference strain), highly polymorphic regions (HPRs) were identified, showing a considerable number of single nucleotide polymorphisms (SNPs). After confirmation by Sanger sequencing, 18 HPRs were used to design a primer panel for multiplex PCR to establish a multilocus Ion AmpliSeq typing method. Toxoplasma gondii isolates and T. gondii present in clinical samples were typed with the new method. The sensitivity of the method was tested with serially diluted reference DNA samples. RESULTS: Among type II specimens, the method could differentiate the same number of haplotypes as the reference standard, microsatellite (MS) typing. Passages of the same isolates and specimens originating from abortion outbreaks were identified as identical. In addition, seven different genotypes, two atypical and two recombinant specimens were clearly distinguished from each other by the method. Furthermore, almost all SNPs detected by the Ion AmpliSeq method corresponded to those expected based on WGS. By testing serially diluted DNA samples, the method exhibited a similar analytical sensitivity as MS typing. CONCLUSION: The new method can distinguish different T. gondii genotypes and detect intra-genotype variability among European type II T. gondii strains. Furthermore, with WGS data additional target regions can be added to the method to potentially increase typing resolution.
- MeSH
- Genetic Variation MeSH
- Genotype MeSH
- Humans MeSH
- Multiplex Polymerase Chain Reaction MeSH
- Polymorphism, Restriction Fragment Length MeSH
- DNA, Protozoan genetics MeSH
- Pregnancy MeSH
- Toxoplasma * genetics MeSH
- High-Throughput Nucleotide Sequencing MeSH
- Check Tag
- Humans MeSH
- Pregnancy MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
