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PubMed1988

Molecular basis and prenatal diagnosis of beta-thalassemia.

The molecular characterization of mutations producing beta-thalassemia in world populations is nearing completion. We expect that new rare alleles in thoroughly studied groups and other alleles in less studied groups, eg, inhabitants of New Guinea, Latin America, and certain Pacific Islands, will be found. Knowledge of the molecular basis of the disease and new technology that allows rapid detection of single nucleotide changes in genomic DNA have led to the reality of prenatal diagnosis by direct mutation detection even in the heterogeneous US population. Programs aimed at prevention of beta-thalassemia should be facilitated by these developments.

Humans↗
PubMedDate not supplied

Recent advances in the development and use of plasma concentrates.

The consequences of blood donations infected with human immunodeficiency virus, the rapid advances in protein fractionation and the introduction of recombinant DNA technology have revolutionized the range of plasma products available to the clinician. This article reviews these developments and describes recent recommendations on their use.

Blood Coagulation Factors↗
PubMed2004

Detection of gyrA and parC mutations associated with ciprofloxacin resistance in Neisseria gonorrhoeae by use of oligonucleotide biochip technology.

An oligonucleotide biochip that specifically detects point mutations in the gyrA and parC genes of Neisseria gonorrhoeae was designed and subsequently evaluated with 87 untreated clinical specimens. The susceptibilities of the N. gonorrhoeae strains were tested to determine the prevalence of ciprofloxacin-resistant strains in Anhui Province, People's Republic of China. Conventional DNA sequencing was also performed to identify mutations in gyrA and parC and to confirm the biochip data. The study demonstrates that all of the point mutations in the gyrA and parC genes of N. gonorrhoeae were easily discriminated by use of the oligonucleotide biochip. Fifteen different alteration patterns involved in the formation of ciprofloxacin resistance were identified by the biochip assay. Double mutations in both Ser91 and Asp95 of the GyrA protein were seen in all nonsensitive isolates. Double mutations in Ser91 and Asp95 of GyrA plus mutation of Glu91 or Ser87 of the ParC protein lead to significant high-level resistance to ciprofloxacin in N. gonorrhoeae isolates. The results obtained by use of the oligonucleotide biochip were identical to those obtained by use of DNA sequencing. In conclusion, the oligonucleotide biochip technology has potential utility for the rapid and reliable identification of point mutations in the drug resistance genes of N. gonorrhoeae.

Anti-Infective Agents↗
PubMed1989

Solution-phase detection of polynucleotides using interacting fluorescent labels and competitive hybridization.

DNA was assayed in a homogeneous format using DNA probes containing hybridization-sensitive labels. The DNA probes were prepared from complementary DNA strands in which one strand was covalently labeled on the 5'-terminus with fluorescein and the complementary strand was covalently labeled on the 3'-terminus with a quencher of fluorescein emission, either pyrenebutyrate or sulforhodamine 101. Probes prepared in this manner were able to detect unlabeled target DNA by competitive hybridization producing fluorescence signals which increased with increasing target DNA concentration. A single pair of complementary probes detected target DNA at a concentration of approximately 0.1 nM in 10 min or about 10 pM in 20-30 min. Detection of a 4 pM concentration of target DNA was demonstrated in 6 h using multiple probe pairs. The major limiting factors were background fluorescence and hybridization rates. Continuous monitoring of fluorescence during competitive hybridization allowed correction for variable sample backgrounds at probe concentrations down to 20 pM; however, the time required for complete hybridization increased to greater than 1 h at probe concentrations below 0.1 nM. A promising application for this technology is the rapid detection of amplified polynucleotides. Detection of 96,000 target DNA molecules in a 50-microliters sample was demonstrated following in vitro amplification using the polymerase chain reaction technique.

Affinity Labels↗
PubMed1999

Construction and analysis of arrayed cDNA libraries.

For any attempt to understand the biology of an organism the incorporation of a cDNA-based approach is unavoidable, because it is a major approach to studying gene function. The complete sequence of the genome alone is not sufficient to understand any organism; its gene regulation, expression, splice variation, posttranslational modifications, and protein-protein interactions all need to be addressed. Because the majority of vertebrate genes have probably been identified as ESTs the next stage of the Human Genome Project is attributing functional information to these sequences. In most cases hybridization-based approaches on arrayed pieces of DNA represent the most efficient way to study the expression level and splicing of a gene in a given tissue. Similar technology, now being applied at the protein level using protein expression libraries, high-density protein membranes, and antibody screening, should allow studies of protein localization and modifications. Coupled to these approaches is the use of technologies, which although lacking the highly parallel nature of hybridization, can potentially characterize large numbers of samples individually and with high accuracy. Automated gel-based DNA sequencing is an example of such a technique; protein sequencing and mass fingerprinting are further examples. In the case of mass spectroscopic analysis, the speed and sensitivity are vastly superior to that of gel-based approaches; however, the preparation of samples is more tedious. Our laboratory is developing a system to characterize DNA samples by mass spectrometry, allowing more rapid genotyping than is currently possible using gel-based technologies ([symbol: see text]. Gut, [symbol: see text]. Berlin and H. Lehrach, personal communication, 1998). Such technology would make information on gene polymorphisms widely accessible. Data generated using all of these techniques at the DNA and protein level will be connected by both protein expression libraries and database comparisons; finally, two hybrid library screens will identify many of the protein-protein interactions, linking genes together. In this way we will start to understand the interplay between genes on a global scale, both at the level of molecular interaction and the biological processes they regulate.

Alternative Splicing↗
PubMed2026

Benchmarking DNA extraction protocols across use cases for culture-independent Nanopore metagenomics.

Oxford Nanopore Technologies (ONT) sequencing offers several advantages for metagenomics, including long reads, rapid turnaround, low upfront cost, scalability and portability. However, for ONT metagenomics, DNA yield, quality and integrity are important considerations when selecting an extraction method. Many metagenomic extraction methods use harsh lysis conditions to extract a wide range of species and provide an accurate community composition, but these conditions can compromise DNA fragment length. Therefore, extraction methods for ONT metagenomics must balance DNA shearing and recovery with representative community lysis. We systematically evaluated DNA extraction methods for ONT metagenomic sequencing using a use case-oriented framework. Among nearly 50 extraction methods screened, 7 were selected for detailed comparison based on suitability for metagenomics, variation in methodology, availability, cost and processing time: Norgen BioTek Corp's Stool DNA Isolation (NG), Zymo Research's ZymoBIOMICS Quick-DNA HMW MagBead (ZMG), Qiagen's DNeasy Blood and Tissue (QBT), Macherey-Nagel's NucleoMag DNA Microbiome (MN), Zymo Research's ZymoBIOMICS DNA Mini Prep (ZMI), Qiagen's DNeasy PowerSoil/QIAamp PowerFecal Pro (PS) and Qiagen's QIAamp Fast DNA Stool Mini (QIA). Methods were tested using Zymo Research's ZymoBIOMICS Microbial Community Standard (MCS), a matrix-free mock community with known composition. DNA extracts were sequenced on an ONT PromethION using the Rapid Barcoding Kit, except QIA due to insufficient DNA yield. Metrics for the method, DNA extracts, sequencing and genomes were evaluated, revealing trade-offs between methods. The two magnetic bead methods, MN and ZMG, produced the highest mean read length N50 values (13.9 and 16.5 kb, respectively) but showed apparent community compositions skewed towards Gram-negative bacteria. In contrast, ZMI and PS maintained a community composition close to expected, with reduced mean read length N50 values (4.5 vs. 7.5 kb). Performance across various metrics is presented in the context of the following use cases: maximizing genome coverage and assembly completeness, preserving composition accuracy, targeting specific species and limiting required resources (equipment, time or budget). The metrics and use case considerations presented offer practical guidance for informed selection of DNA extraction methods for ONT metagenomics. For accurate community composition, ZMI or PS are recommended, while PS and ZMG perform best at maximizing genome coverage and assembly completeness. NG and QBT may be the most economical options, though performance trade-offs were observed. Finally, PS may be the preferred method for time-sensitive diagnostic or field applications.

Metagenomics↗
PubMed1998

Perspective on BRCA1.

In a very real sense, the search for a breast cancer susceptibility gene reflects the rapid evolution of molecular genetics as a field and the power of molecular technology to accelerate the pace of discovery. This search began with the study of blood proteins through biochemical analysis; the number of loci accessible was limited, and very few consistent results were obtained (1). Then came recombinant DNA technology. The number of available markers, and the information they provide, has grown rapidly over the years. The same is true for the development of new, high-throughput genotyping methods and associated informatics systems and statistical methods, making gene mapping more feasible. For BRCA1, it took five years and 183 markers to identify the chromosomal location as 17q21 (2). It took an additional four years before BRCA1 was cloned (3). In contrast, BRCA2 was localized to chromosome 13q12-13 two months before the cloning of BRCA1 was reported; less than two years later, BRCA2 was cloned (4,5). Characterization of these two genes is still underway, in part, because of unanticipated complexity. This complexity plays out at multiple levels, including the relationship between phenotype and genotype within and between the populations studied, biological function(s), and social consequences. The reviews presented in this issue reflect the breadth of impact that the discovery of the BRCA genes has had on science, medicine, and law. As with most great discoveries, the identification of BRCA1 has forced us to question the fundamentals of our belief systems: what is a mutation, what is a tumor suppressor, what is righteous, and what is ethical?

Journal Article↗
PubMed2001

DNA analysis on electrophoretic microchips: effect of operational variables.

Applicability of modern microfabrication technology to electrophoresis microchips initiated a rapidly moving interdisciplinary field in analytical chemistry. Electric field mediated separations in microfabricated devices (electrophoresis microchips) are significantly faster than conventional gel electrophoresis, usually completed in seconds to minutes. Electrophoretic separation of DNA molecules on microfabricated devices proved to have the potential to improve the throughput of analysis by orders of magnitude. The flexibility of electrophoresis microchips allows the use of a plethora of separation matrices and conditions. In this paper, we report on electric field mediated separation of fluorescent intercalator-labeled dsDNA fragments in polyvinylpyrrolidone matrix-filled microchannel structures. The separations were detected in real time by a confocal, single-point laser-induced fluorescence/photomultiplier setup. Effects of the sieving matrix concentration (Ferguson plot), migration characteristics (reptation plot), separation temperature (Arrhenius plot), as well as applied electric field strength and intercalator concentration on the separation of DNA fragments are thoroughly discussed.

DNA↗
PubMed2026

OligoSeq: Rapid nanopore-sequencing of single-stranded oligonucleotides.

Nanopore-based DNA sequencing technology has achieved remarkable success in sequencing increasingly long DNA strands (e.g., over a million nucleotides long) for genomics research and biotechnology applications. However, the same level of progress has not been achieved for DNA oligonucleotides (usually ≤ 300 nucleotides long). Oligonucleotides play a crucial role in genome engineering efforts through oligo library generation and in DNA data storage, where they are used to encode computer information, such as binary (digital) data in DNA libraries. To enable these applications, accurate sequencing of oligonucleotides in a way that allows to assess for sequence variability, quality and length is essential. But sequencing solutions for oligonucleotides - particularly DNA primers for PCR, oligo DNA libraries used for mutagenesis or cDNA libraries used in gene expression analysis - remain inadequate. To address this gap, OligoSeq is presented as an innovative approach that integrates two complementary techniques: AmpliSeq (based on PCR) and RevSeq (based on reverse complementation with sequence-specific or random primers) to facilitate sequencing of single-stranded oligonucleotides using reference sequence anchor matches of more than ≥ 90% identity spanning from about 70% to 10% with AmpliSeq or RevSeq with random nonamers, respectively, and resolving the final reference sequence based on the most likely candidate from basecall frequencies, regardless of length and double-stranding method. OligoSeq can be integrated with nanopore sequencing technology pipelines and can be used as a reference for other sequencing platforms requiring double-stranded adapters, offering a practical and scalable alternative for standard quality control in single-stranded oligonucleotide synthesis. The use of nanopore technology, compatible with the double-stranding methods showcased, is shown to be the most cost-effective method for resolving original DNA sequences of different length and quality, and to assess its sequence variability, compared to other methods such as Illumina, PacBio or HPLC/MS.

Sequence Analysis, DNA↗
PubMed1998

[The DNA-chip, a new tool for medical genetics].

The DNA (chip) technology, emerged in the last two years, provides an incredible technical development in rapid and automatised performance of genetic identification. The principle of procedure is, that by series of photolitographic and chemical steps on solid-phase of a small surface relatively dense oligonucleotide arrays can be generated. The oligonucleotides produced by the computer-directed in-situ microfabrication may bind complementary fluorescent-labeled DNA fragments from the unknown sample. After scanning, the registered position of positive signals provide information on the identity of DNA fragments. By this novel approach not only DNA sequencing can be performed, but genetic errors of known genes, presence of infectious organisms and the typing of genetic markers (such as HLA) used for transplantation and forensic medicine can be determined. The DNA-chip technology is a revolutionary new milestone in genetic diagnose.

DNA↗
PubMed2000

Screening for genetic mutations. A review.

A point mutation of a nucleotide within a single gene can have a profound effect on a specific organ and/or the entire human body. DNA sequences associated with human diseases may differ from the corresponding normal sequences by single nucleotide mutations or by large alterations such as deletions, insertions, duplications, or translocations of DNA segments or entire chromosomes. As a result of the heterogeneity of DNA alterations and genetic mutations, various screening approaches are required to detect these alterations. However, methods which facilitate the detection of large mutations in the genome are typically insensitive to point mutations, whereas methods which detect point mutations are not appropriate to detect large alterations within the genome. Since there is no single perfect method to screen for unknown mutations, combinations of these methods may be necessary for accurate genetic diagnosis. The applications of polymerase chain reaction (PCR) technology to genomic screening have made rapid and accurate genetical diagnosis possible. Furthermore, recent developments in the technology of DNA microarrays have opened the way for high throughput sequence analysis by hybridization, which shows great potential in both molecular biology and medicine in the near future.

Genetic Testing↗
PubMed2001

Use of up-converting phosphor reporters in lateral-flow assays to detect specific nucleic acid sequences: a rapid, sensitive DNA test to identify human papillomavirus type 16 infection.

BACKGROUND: A lateral-flow (LF) device using the new reporter up-converting phosphor technology (UPT) was applied to DNA (hybridization) assays for the detection of specific nucleic acid sequences, thereby aiming to perform the test outside well-equipped laboratories. The methodology reported here is sensitive and provides a rapid alternative for more elaborate gel electrophoresis and Southern blotting. In a preliminary study, it was applied to screen for the presence of human papillomavirus type 16 (HPV16) in a defined series of cervical carcinomas. METHODS: A LF assay was used to capture haptenized DNA molecules and hybrids, which were immunolabeled (before LF) with 400-nm UPT particles. These particles emit visible light after excitation with infrared in a process called up-conversion. Because up-conversion occurs in only the phosphor lattice, autofluorescence of other assay components is virtually nonexistent. RESULTS: The use of the UPT reporter in LF-DNA tests, as compared with colloidal gold, improved the detection limit at least 100-fold. UPT LF-DNA tests were successfully applied to detect (in a blind test) the presence of HPV16 in DNA extracts obtained from cervical carcinomas. Test results matched 100% with previous characterization of these carcinomas. CONCLUSIONS: The use of UPT in LF assays to detect specific nucleic acids provides low attamole-range sensitivity. Hybridization and consecutive detection of PCR-amplified HPV16 sequences were successful in a background of 10 microg of fish-sperm DNA. The sensitivity of UPT detection in these complex mixtures indicates that detection of viral infections without PCR or other amplification technique is achievable.

Antibodies, Monoclonal↗
PubMed2000

Rapid analysis of amplified double-stranded DNA by capillary electrophoresis with laser-induced fluorescence detection.

DNA amplification technology has been applied to clinical diagnosis of infectious disease, genetic disorder, and cancer. After in vitro amplification of a particular DNA region, the methods of analysis for these amplified samples play a pivotal role in clinical diagnosis. Conventional gel electrophoresis has been routinely used in the lab for checking DNA. The whole procedure is time consuming and requires more than 1 ng of DNA for detection. To achieve greater performance in DNA diagnosis, we demonstrated capillary electrophoresis with laser induced fluorescence detection for analysis of amplified DNA. The analysis of DNA could be completed within 3 min and the data is directly entered into the computer. Considering the automatic and rapid process, we believe that this method could be routinely utilized for the clinical diagnosis of amplified DNA products.

DNA↗
PubMed2005

Diagnosis of herpes simplex virus infections of the CNS.

Advances in the diagnosis of herpes simplex virus infections of the CNS have occurred rapidly over the past 10 years. The development and application of PCR technology to the detection of herpes simplex virus DNA from cerebrospinal fluid has resulted in tremendous improvements in the management of patients with suspected herpes simplex virus CNS infections, not the least of which is decreasing the necessity for invasive brain biopsy to establish the diagnosis. The pace of discovery has continued in recent years with the development of more rapid DNA amplification techniques that do not require postamplification analysis using amplified products (real-time PCR). However, despite the power of these new diagnostic modalities, test results must always be considered in the context of the patient, and physician judgment should never be usurped by technological advances. This article will summarize the advances in the diagnosis of herpes simplex virus CNS disease within the context of how these advances can enhance the care of individual patients.

Animals↗
PubMed2005

Aptamers--basic research, drug development, and clinical applications.

Since its discovery in the early 1990s, aptamer technology has progressed tremendously. Automated selection procedures now allow rapid identification of DNA and RNA sequences that can target a broad range of extra- and intracellular proteins with nanomolar affinities and high specificities. The unique binding properties of nucleic acids, which are amenable to various modifications, make aptamers perfectly suitable for different areas of biotechnology. Moreover, the approval of an aptamer for vascular endothelial growth factor by the US Food and Drug Administration highlights the potential of aptamers for therapeutic applications. This review summarizes recent developments and demonstrates that aptamers are valuable tools for diagnostics, purification processes, target validation, drug discovery, and even therapeutic approaches.

Animals↗
PubMed2004

Searching for cancer-associated gene polymorphisms: promises and obstacles.

Low-penetrance genetic variations appear to form the most essential component of the heritability of cancer risk. Search for relevant polymorphic candidates faces significant obstacles, due to both the high number of potentially promising single nucleotide polymorphisms (SNPs) and the intrinsic difficulties in identification of weak gene-disease interactions. At present, extensive case-control studies can be applied only to a limited number of gene polymorphisms. Therefore, the choice of SNPs that deserve an exhaustive populational analysis is of primary importance. Preferences are usually given to those genetic pathways, whose variability and role in cancer causation have been already shown by prior studies. The available electronic databases and software tools may allow further SNP sorting, based on functional predictions. The design for the pilot study may need to be different from the one for large-scale case-control analysis. Some investigations justify non-random patient selection for preliminary assessment of low-penetrance effects, with the emphasis on particularly susceptible individuals (familial, early onset, multiple cancer cases). Other presumably accelerating approaches suggest a decisive exclusion of SNP candidates showing only marginal effects, relaxed formats for rapid dissemination of preliminary data, use of more demonstrative controls such as elderly tumor-free subjects, etc. These short-cuts cannot be properly validated for the time being, due to the paucity of identified low-penetrance risk modifiers. It is expected that the increasing capacities of available DNA collections, coupled with the rapid development of high-throughput genotyping technologies, will vastly accelerate the research on polygenic cancer susceptibility.

Alleles↗
PubMed2001

Glycoengineering of therapeutic glycoproteins: in vitro galactosylation and sialylation of glycoproteins with terminal N-acetylglucosamine and galactose residues.

Therapeutic glycoproteins produced in different host cells by recombinant DNA technology often contain terminal GlcNAc and Gal residues. Such glycoproteins clear rapidly from the serum as a consequence of binding to the mannose receptor and/or the asialoglycoprotein receptor in the liver. To increase the serum half-life of these glycoproteins, we carried out in vitro glycosylation experiments using TNFR-IgG, an immunoadhesin molecule, as a model therapeutic glycoprotein. TNFR-IgG is a disulfide-linked dimer of a polypeptide composed of the extracellular portion of the human type 1 (p55) tumor necrosis factor receptor (TNFR) fused to the hinge and Fc regions of the human IgG(1) heavy chain. This bivalent antibody-like molecule contains four N-glycosylation sites per polypeptide, three in the receptor portion and one in the Fc. The heterogeneous N-linked oligosaccharides of TNFR-IgG contain sialic acid (Sia), Gal, and GlcNAc as terminal sugar residues. To increase the level of terminal sialylation, we regalactosylated and/or resialylated TNFR-IgG using beta-1,4-galactosyltransferase (beta1,4GT) and/or alpha-2,3-sialyltransferase (alpha2,3ST). Treatment of TNFR-IgG with beta1,4GT and UDP-Gal, in the presence of MnCl(2), followed by MALDI-TOF-MS analysis of PNGase F-released N-glycans showed that the number of oligosaccharides with terminal GlcNAc residues was significantly decreased with a concomitant increase in the number of terminal Gal residues. Similar treatment of TNFR-IgG with alpha2,3ST and CMP-sialic acid (CMP-Sia), in the presence of MnCl(2), produced a molecule with an approximately 11% increase in the level of terminal sialylation but still contained oligosaccharides with terminal GlcNAc residues. When TNFR-IgG was treated with a combination of beta1,4GT and alpha2,3ST (either in a single step or in a stepwise fashion), the level of terminal sialylation was increased by approximately 20-23%. These results suggest that in vitro galactosylation and sialylation of therapeutic glycoproteins with terminal GlcNAc and Gal residues can be achieved in a single step, and the results are similar to those for the stepwise reaction. This type of in vitro glycosylation is applicable to other glycoproteins containing terminal GlcNAc and Gal residues and could prove to be useful in increasing the serum half-life of therapeutic glycoproteins.

Acetylglucosamine↗
PubMed2004

High-speed detection of the G894T polymorphism in exon 7 of the eNOS gene by real-time fluorescence PCR with the Light-Cycler.

In endothelial cells nitric oxide (NO) is synthesized by endothelial-nitric oxide synthase (e-NOS), constitutively expressed and encoded by a 26-exon gene, located on chromosome 7q35-36. The prevalence of the T rare variant of the G894T polymorphism in exon 7 of the e-NOS gene (Glu-->Asp amino acid substitution) has been reported to be significantly higher in patients with coronary spasm and coronary artery disease. To date G894T polymorphism detection is performed by PCR-RFLP assay. In order to establish a high-speed genotyping method, we have taken advantage of the Light Cycler instrument, a thermal cycler that combines rapid-cycle DNA amplification with a real-time fluorescence monitoring. This technology is based on hybridization of the adjacent fluorescently labeled probes with PCR products. This methodology is considered more accurate and less time-consuming than conventional PCR-RFLP assay. To validate this technique we genotyped 270 healthy subjects. The results were consistent with those obtained from PCR-RFLP assay.

Alleles↗