Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Oligonucleotide Array Sequence Analysis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24Linked to original sources
PubMed2002

Discriminant analysis to evaluate clustering of gene expression data.

In this work we present a procedure that combines classical statistical methods to assess the confidence of gene clusters identified by hierarchical clustering of expression data. This approach was applied to a publicly released Drosophila metamorphosis data set [White et al., Science 286 (1999) 2179-2184]. We have been able to produce reliable classifications of gene groups and genes within the groups by applying unsupervised (cluster analysis), dimension reduction (principal component analysis) and supervised methods (linear discriminant analysis) in a sequential form. This procedure provides a means to select relevant information from microarray data, reducing the number of genes and clusters that require further biological analysis.

Animals↗
PubMed2002

Specificity of mammalian Y-box binding protein p50 in interaction with ss and ds DNA analyzed with generic oligonucleotide microchip.

p50 protein is a member of the Y-box binding transcription factor family and is a counterpart of YB-1 protein. The generic microchip was used to analyze the sequence specificity of p50 binding to single (ss) and double-stranded (ds) oligodeoxyribonucleotides. The generic microchip contained 4,096 single-stranded octadeoxyribonucleotides in which all possible core 6-mers (4(6)=4,096) were flanked at their 3' and 5'-ends with degenerated nucleotides. The oligonucleotides were chemically immobilized within polyacrylamide gel pads fixed on a glass slide. The binding of p50 to the generic microchip was shown to be the most specific to ss GGGG motif and then to ss CACC and CATC motifs. GC-rich ds oligonucleotides of the generic microchip, and particularly those containing GGTG/CACC, GATG/CATC, and GTGG/CCAC heterogeneous motifs, were most efficiently destabilized due to interaction with p50. Gel-shift electrophoresis has shown that the protein exhibits much higher binding specificity to 24-mer oligoA-TGGGGG-oligoA containing G-rich 6-mer, in comparison with 24-mer oligoA-AAATAT-oligoA carrying A,T-rich 6-mer in full correspondence with the data obtained with the microchip. Studies of DNA-binding proteins using gel-immobilized ss and ds DNA fragments provide a unique possibility to detect low-affinity complexes of these proteins with short sequence motifs and assess the role of these motifs in sequence-specific interactions with long recognition sites.

Animals↗
PubMed2002

A simple method to improve probe set estimates from oligonucleotide arrays.

A popular commercially available oligonucleotide microarray technology employs sets of 25 base pair oligonucleotide probes for measurement of gene expression levels. A mathematical algorithm is required to compute an estimate of gene expression from the multiple probes. Previously proposed methods for summarizing gene expression data have either been substantially ad hoc or have relied on model assumptions that may be easily violated. Here we present a new algorithm for calculating gene expression from probe sets. Our approach is functionally related to leave-one-out cross-validation, a non-parametric statistical technique that is often applied in limited data situations. We illustrate this approach using data from our study seeking a molecular fingerprint of STAT3 regulated genes for early detection of human cancer.

Algorithms↗
PubMed2002

Multivariate approach for selecting sets of differentially expressed genes.

An important problem addressed using cDNA microarray data is the detection of genes differentially expressed in two tissues of interest. Currently used approaches ignore the multidimensional structure of the data. However it is well known that correlation among covariates can enhance the ability to detect less pronounced differences. We use the Mahalanobis distance between vectors of gene expressions as a criterion for simultaneously comparing a set of genes and develop an algorithm for maximizing it. To overcome the problem of instability of covariance matrices we propose a new method of combining data from small-scale random search experiments. We show that by utilizing the correlation structure the multivariate method, in addition to the genes found by the one-dimensional criteria, finds genes whose differential expression is not detectable marginally.

Algorithms↗
PubMed2003

Detection and discrimination of orthopoxviruses using microarrays of immobilized oligonucleotides.

Variola virus (VARV), causing smallpox, is a potential biological weapon. Methods to detect VARV rapidly and to differentiate it from other viruses causing similar clinical syndromes are needed urgently. We have developed a new microarray-based method that detects simultaneously and discriminates four orthopoxvirus (OPV) species pathogenic for humans (variola, monkeypox, cowpox, and vaccinia viruses) and distinguishes them from chickenpox virus (varicella-zoster virus or VZV). The OPV gene C23L/B29R, encoding the CC-chemokine binding protein, was sequenced for 41 strains of seven species of orthopox viruses obtained from different geographical regions. Those C23L/B29R sequences and the ORF 62 sequences from 13 strains of VZV (selected from GenBank) were used to design oligonucleotide probes that were immobilized on an aldehyde-coated glass surface (a total of 57 probes). The microchip contained several unique 13-21 bases long oligonucleotide probes specific to each virus species to ensure redundancy and robustness of the assay. A region approximately 1100 bases long was amplified from samples of viral DNA and fluorescently labeled with Cy5-modified dNTPs, and single-stranded DNA was prepared by strand separation. Hybridization was carried out under plastic coverslips, resulting in a fluorescent pattern that was quantified using a confocal laser scanner. 49 known and blinded samples of OPV DNA, representing different OPV species, and two VZV strains were tested. The oligonucleotide microarray hybridization technique identified reliably and correctly all samples. This new procedure takes only 3 h, and it can be used for parallel testing of multiple samples.

DNA Primers↗
PubMed2002

Stem-loop oligonucleotides: a robust tool for molecular biology and biotechnology.

The specific structural features of stem-loop (hairpin) DNA constructs provide increased specificity of target recognition. Recently, several robust assays have been developed that exploit the potential of structurally constrained oligonucleotides to hybridize with their cognate targets. Here, I review new diagnostic approaches based on the formation of stem-loop DNA oligonucleotides: molecular beacon methodology, suppression PCR approaches and the use of hairpin probes in DNA microarrays. The advantages of these techniques over existing ones for sequence-specific DNA detection, amplification and manipulation are discussed.

Base Sequence↗
PubMed2002

The developments of semisynthetic DNA-protein conjugates.

Semisynthetic DNA-protein conjugates, generated by either covalent or non-covalent coupling chemistry, are versatile molecular tools applicable in bioanalytical and synthetic chemical procedures. This article reviews the synthesis and characterization of artificial nucleic acid-protein conjugates, in addition to applications arising in the life sciences and nanobiotechnology, such as the self-assembly of high-affinity reagents for immunological detection assays and biosensors, the fabrication of laterally microstructured biochips, and the biomimetic 'bottom-up' synthesis of nanostructured supramolecular devices.

Binding Sites↗
PubMed2003

Partitioning large-sample microarray-based gene expression profiles using principal components analysis.

Principal components analysis (PCA) is useful for reproducing the total variation among hundreds or thousands of continuously-scaled variables with a much smaller number of unobservable variables called 'latent factors'. The CLUSFAVOR computer program was used to implement PCA for identifying groups of genes with similar expression profiles from a large number of genes used on DNA microarrays. This paper describes the principal components solution to the factor model of the correlation matrix R, calculation of eigenvalues and eigenvectors of R, extraction of factors, and calculation of factor loadings and identification of genes with similar loading patterns to construct groups of genes with similar expression profiles. With regard to extraction of factors, it was found that more than 90% of the total variance in input data could be accounted for by extracting factors whose eigenvalues exceed unity. Bipolar factors containing strong positive and negative loadings can also be used for identifying two unique groups of genes, since expression profiles of genes that load positive are unlike expression profiles of genes that load negative on the same factor. While PCA does not provide the absolute answer to a multidimensional problem, it nevertheless can provide a heuristic with which natural groupings of genes with similar expression profiles can be assembled. While cluster analysis essentially generates a single dendogram (tree branch) containing every gene in the input data, PCA can be used to assemble gene expression profiles that strongly correlate with the latent factors accounting for a majority of total variance. Example results for CLUSFAVOR computer program runs are provided.

Gene Expression Profiling↗
PubMed2003

Gene and protein expression profiling of human cerebral endothelial cells activated with tumor necrosis factor-alpha.

An increase in permeability of the blood-brain barrier is a critical event in the pathophysiological process of multiple sclerosis and other neurodegenerative diseases. Tumor necrosis factor alpha (TNFalpha) is known to play a crucial role in this process and is a powerful activator of endothelial cell inflammatory responses. Although many reports describe effects of TNFalpha activation in endothelial cells, the molecular mechanisms specific for activation of cerebral endothelial cells remains unclear. The objective of this study was to identify potential pharmaceutical targets for the treatment of multiple sclerosis using molecular profiling techniques. Gene expression measurements (Affymetrix Hu6800 oligonucleotide arrays) and proteomics (two-dimensional gel electrophoresis and mass spectrometry) were applied to analyze early alterations in human cerebral endothelial cells (HCEC) activated by TNFalpha. Human umbilical vein endothelial cells (HUVEC) were used as the reference system. The results presented show that HCEC and HUVEC respond similarly with respect to cell adhesion molecules, chemotaxis, apoptosis and oxidative stress molecules. However, nuclear factors NFkB1 and NFkB2, plasminogen activator inhibitor 1 and cofilin 1 are examples of cerebral specific responses. Our results indicate involvements of the urokinase plasminogen activator system and cytoskeletal rearrangements unique to TNFalpha activation of cerebral endothelial cells.

Antineoplastic Agents↗
PubMed2003

Analysis of gene expression profiles: an application of memetic algorithms to the minimum sum-of-squares clustering problem.

Microarrays have become a key technology in experimental molecular biology since they allow monitoring of gene expression for more than 10,000 genes in parallel producing huge amounts of data. In the exploration of transcriptional regulatory networks, an important task is to cluster gene expression data to identify groups of genes with similar patterns and hence similar function. In this paper, memetic algorithms (MAs)-evolutionary algorithms incorporating local search-are proposed for minimum sum-of-squares clustering (MSSC). In a fitness landscape analysis, it is shown that the MSSC problem has correlation structure exploitable by MAs. The proposed MAs are shown to be superior to multi-start k-means as well as five other clustering algorithms from the bioinformatics literature including hierarchical algorithms and self-organizing maps. Although the fitness values of the different clustering solutions lie close together, it is shown that the solutions differ significantly from each other in terms of cluster memberships which is extremely important for the biological interpretation of the clustering results.

Algorithms↗
PubMed2003

Multi locus fingerprinting of Listeria monocytogenes by sequence-specific labeling of DNA probes combined with array hybridization.

We have developed an alternative multi locus sequence typing (MLST) approach that targets the variable genetic changes directly in a DNA array format. Our approach is based on DNA array hybridization in combination with sequence-specific labeling of oligonucleotide probes. Listeria monocytogenes was chosen for the development and evaluation of the assay. The genes hlyA, iap, flaA, inlA and actA were targeted. Twenty-nine suitable probe regions were identified within these genes. The DNA array results from 32 different strains were compared to serotype and amplified fragment length polymorphism data. This comparison showed that our DNA array method gave good discrimination between the strains analyzed. In conclusion, the DNA array-based MLST method is a promising tool for fingerprint bacteria.

Bacterial Typing Techniques↗
PubMed2003

Design and development of a DNA array for rapid detection and identification of multiple tomato vascular wilt pathogens.

Fusarium wilt, caused by Fusarium oxysporum f. sp. lycopersici, and Verticillium wilt, caused by either Verticillium albo-atrum or Verticillium dahliae, are devastating diseases of tomato (Lycopersicon esculentum) found worldwide. Monitoring is the cornerstone of integrated pest management of any disease. The lack of rapid, accurate, and reliable means by which plant pathogens can be detected and identified is one of the main limitations in integrated disease management. In this paper, we describe the development of a molecular detection system, based on DNA array technology, for rapid and efficient detection of these vascular wilt pathogens. We show the utility of this array for the sensitive detection of these pathogens from complex substrates like soil, plant tissues and irrigation water, and samples that are collected by tomato growers in their greenhouses.

DNA, Bacterial↗
PubMed2003

Blocking oligo--a novel approach for improving chip-based DNA hybridization efficiency.

For most of the commonly used DNA chips, the probes are usually single-stranded oligonucleotides and the targets are double-stranded DNAs (dsDNAs). Only one strand of the DNA serves as the target while the other competes with the probes immobilized on the chip for the target and therefore is regarded as the interfering strand. In this report, a novel technique was developed for improving the hybridization efficiency on DNA chips by using blocking oligos, which is complimentary to the target interfering strand to reduce the influence of the interfering strand. The hybridization efficiency of dsDNA was much lower than that of single-stranded DNA (ssDNA) when synthesized DNA targets were tested on the DNA chip. Blocking oligos can improve the hybridization efficiency of dsDNA to about 2/3 that of ssDNA. Blocking oligos have also been applied to PCR products of different lengths for hybridization. The hybridization efficiency with blocking oligos is about three times higher than that without blocking oligos. We have tested PCR products of 1054 and 435 bp using our blocking procedure, and the results are consistent.

DNA↗
PubMed2001

CYP2D6 genotyping with oligonucleotide microarrays and nortriptyline concentrations in geriatric depression.

Recent advances in oligonucleotide microarray technology ("gene chips") permit rapid screening for DNA sequence variation. The CYP2D6 gene encodes debrisoquine hydroxylase, which metabolizes the antidepressant nortriptyline and other psychotropic medications. Nortriptyline plasma concentrations were obtained after at least three weeks of treatment in 36 geriatric patients with major depression who were taking a mean of 8.6 other medications besides nortriptyline. Oligonucleotide microarrays were used to detect 16 CYP2D6 alleles that affect debrisoquine hydroxylase activity. Subjects carrying alleles encoding impaired debrisoquine hydroxylase activity had significantly greater nortriptyline concentrations and lower nortriptyline doses than did other subjects. Significant correlations were found between the numbers of alleles encoding decreased metabolism and nortriptyline plasma concentration, nortriptyline dose, and nortriptyline plasma concentration standardized for dose, indicating a gene dosage effect. These results demonstrate that CYP2D6 genotyping on a microarray platform can be used to predict plasma antidepressant concentrations despite advanced patient age and numerous concurrent medications.

Aged↗
PubMed2003

Achieving differentiation of single-base mutations through hairpin oligonucleotide and electric potential control.

A novel assay for surface DNA hybridization, which is free of sample and probe labeling, convenient and of low cost, sensitive and capable of differentiation of single-base mutations, is reported. Hairpin oligonucleotides are carefully designed as probes and are covalently attached to Si chips. Segments of the human p53 gene are chosen to demonstrate the major features of the novel technique. Impedance measurement is used to detect the hybridization. To further optimize the performance, electric potential is applied on the chip. The apparently different responses of the chip to the complementary strand and the single-base mutant are shown under electric potential control. The criteria on the design of the hairpin oligonucleotides are discussed.

Biosensing Techniques↗