SEARCH · PubMed Health

Results for “comparative genomics”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 19 recordsLinked to original sources

PubMed2005

A tiered approach to comparative genomics.

Comparative genomics has emerged as a valuable tool for locating genes, transcription factor motifs and other putative control regions. There are, however, issues that keep comparative genomics from being a straightforward process. These caveats fall into three categories: database, computational and biological. In this review paper, these caveats will be discussed and illustrated using related case studies. The National Center for Biotechnology Information and University of California Santa Cruz genome databases were used, and VISTA, LAGAN and zPicture were used as comparison tools. Based on these caveats, a tiered approach to carrying out comparative genomic studies is presented.

Algorithms↗

PubMed2001

The evolution of mycobacterial pathogenicity: clues from comparative genomics.

Comparative genomics, and related technologies, are helping to unravel the molecular basis of the pathogenesis, host range, evolution and phenotypic differences of the slow-growing mycobacteria. In the highly conserved Mycobacterium tuberculosis complex, where single-nucleotide polymorphisms are rare, insertion and deletion events (InDels) are the principal source of genome plasticity. InDels result from recombinational or insertion sequence (IS)-mediated events, expansion of repetitive DNA sequences, or replication errors based on repetitive motifs that remove blocks of genes or contract coding sequences. Comparative genomic analyses also suggest that loss of genes is part of the ongoing evolution of the slow-growing mycobacterial pathogens and might also explain how the vaccine strain BCG became attenuated.

Amino Acid Sequence↗

PubMed2004

Sockeye: a 3D environment for comparative genomics.

Comparative genomics techniques are used in bioinformatics analyses to identify the structural and functional properties of DNA sequences. As the amount of available sequence data steadily increases, the ability to perform large-scale comparative analyses has become increasingly relevant. In addition, the growing complexity of genomic feature annotation means that new approaches to genomic visualization need to be explored. We have developed a Java-based application called Sockeye that uses three-dimensional (3D) graphics technology to facilitate the visualization of annotation and conservation across multiple sequences. This software uses the Ensembl database project to import sequence and annotation information from several eukaryotic species. A user can additionally import their own custom sequence and annotation data. Individual annotation objects are displayed in Sockeye by using custom 3D models. Ensembl-derived and imported sequences can be analyzed by using a suite of multiple and pair-wise alignment algorithms. The results of these comparative analyses are also displayed in the 3D environment of Sockeye. By using the Java3D API to visualize genomic data in a 3D environment, we are able to compactly display cross-sequence comparisons. This provides the user with a novel platform for visualizing and comparing genomic feature organization.

Animals↗

PubMed1998

Background and Overview of Comparative Genomics.

Comparative genomics---the cross-referencing of information on genome organization between species---provides an additional dimension to the Human Genome Project and can derive much information from it for the benefit of animal health and animal breeding. Arrangements of genes and other DNA sequences may be determined by a variety of genetic and physical techniques, at resolutions from the gross cytological level to the level of the single base pair. Gross arrangements and rearrangements can also be charted by comparative chromosome painting. Genome organization may then be compared across mammal---and other vertebrate---species. Genetic mapping is well advanced in several livestock species as well as rodent model species, and outline maps are available for at least 30 mammal species in eight orders. At the time of this writing, maps are being rapidly constructed for chicken and fish species. Comparisons, even over vast evolutionary time scales, show that the mammal genome---indeed, the vertebrate genome---has been highly conserved. Thus, information about location and function of genes is directly transferable across species and should greatly accelerate the search for genes that specify inherited diseases in domestic mammals and humans as well as genes that specify economically important traits.

Journal Article↗

PubMed2004

Eukaryotic regulatory element conservation analysis and identification using comparative genomics.

Comparative genomics is a promising approach to the challenging problem of eukaryotic regulatory element identification, because functional noncoding sequences may be conserved across species from evolutionary constraints. We systematically analyzed known human and Saccharomyces cerevisiae regulatory elements and discovered that human regulatory elements are more conserved between human and mouse than are background sequences. Although S. cerevisiae regulatory elements do not appear to be more conserved by comparison of S. cerevisiae to Schizosaccharomyces pombe, they are more conserved when compared with multiple other yeast genomes (Saccharomyces paradoxus, Saccharomyces mikatae, and Saccharomyces bayanus). Based on these analyses, we developed a sequence-motif-finding algorithm called CompareProspector, which extends Gibbs sampling by biasing the search in regions conserved across species. Using human-mouse comparison, CompareProspector identified known motifs for transcription factors Mef2, Myf, Srf, and Sp1 from a set of human-muscle-specific genes. It also discovered the NFAT motif from genes up-regulated by CD28 stimulation in T-cells, which implies the direct involvement of NFAT in mediating the CD28 stimulatory signal. Using Caenorhabditis elegans-Caenorhabditis briggsae comparison, CompareProspector found the PHA-4 motif and the UNC-86 motif. CompareProspector outperformed many other computational motif-finding programs, demonstrating the power of comparative genomics-based biased sampling in eukaryotic regulatory element identification.

Algorithms↗

PubMed2004

SeeGH--a software tool for visualization of whole genome array comparative genomic hybridization data.

BACKGROUND: Array comparative genomic hybridization (CGH) is a technique which detects copy number differences in DNA segments. Complete sequencing of the human genome and the development of an array representing a tiling set of tens of thousands of DNA segments spanning the entire human genome has made high resolution copy number analysis throughout the genome possible. Since array CGH provides signal ratio for each DNA segment, visualization would require the reassembly of individual data points into chromosome profiles. RESULTS: We have developed a visualization tool for displaying whole genome array CGH data in the context of chromosomal location. SeeGH is an application that translates spot signal ratio data from array CGH experiments to displays of high resolution chromosome profiles. Data is imported from a simple tab delimited text file obtained from standard microarray image analysis software. SeeGH processes the signal ratio data and graphically displays it in a conventional CGH karyotype diagram with the added features of magnification and DNA segment annotation. In this process, SeeGH imports the data into a database, calculates the average ratio and standard deviation for each replicate spot, and links them to chromosome regions for graphical display. Once the data is displayed, users have the option of hiding or flagging DNA segments based on user defined criteria, and retrieve annotation information such as clone name, NCBI sequence accession number, ratio, base pair position on the chromosome, and standard deviation. CONCLUSIONS: SeeGH represents a novel software tool used to view and analyze array CGH data. The software gives users the ability to view the data in an overall genomic view as well as magnify specific chromosomal regions facilitating the precise localization of genetic alterations. SeeGH is easily installed and runs on Microsoft Windows 2000 or later environments.

Chromosome Mapping↗

PubMed2006

Whole genome computational comparative genomics: A fruitful approach for ascertaining Alu insertion polymorphisms.

Alu elements are the most active and predominant type of short interspersed elements (SINEs) in the human genome. Recently inserted polymorphic (for presence/absence) Alu elements contribute to genome diversity among different human populations, and they are useful genetic markers for population genetic studies. The objective of this study is to identify polymorphic Alu insertions through an in silico comparative genomics approach and to analyze their distribution pattern throughout the human genome. By computationally comparing the public and Celera sequence assemblies of the human genome, we identified a total of 800 polymorphic Alu elements. We used polymerase chain reaction-based assays to screen a randomly selected set of 16 of these 800 Alu insertion polymorphisms using a human diversity panel to demonstrate the efficiency of our approach. Based on sequence analysis of the 800 Alu polymorphisms, we report three new Alu subfamilies, Ya3, Ya4b, and Yb11, with Yb11 being the smallest known Alu subfamily. Analysis of retrotransposition activity revealed Yb11, Ya8, Ya5, Yb9, and Yb8 as the most active Alu subfamilies and the maintenance of a very low level of retrotransposition activity or recent gene conversion events involving S subfamilies. The 800 polymorphic Alu insertions are characterized by the presence of target site duplications (TSDs) and longer than average polyA-tail length. Their pre-integration sites largely follow an extended "NT-AARA" motif. Among chromosomes, the density of Alu insertion polymorphisms is positively correlated with the Alu-site availability and is inversely correlated with the densities of older Alu elements and genes.

Alu Elements↗

PubMed2003

Towards the delineation of the ancestral eutherian genome organization: comparative genome maps of human and the African elephant (Loxodonta africana) generated by chromosome painting.

This study presents a whole-genome comparison of human and a representative of the Afrotherian clade, the African elephant, generated by reciprocal Zoo-FISH. An analysis of Afrotheria genomes is of special interest, because recent DNA sequence comparisons identify them as the oldest placental mammalian clade. Complete sets of whole-chromosome specific painting probes for the African elephant and human were constructed by degenerate oligonucleotide-primed PCR amplification of flow-sorted chromosomes. Comparative genome maps are presented based on their hybridization patterns. These maps show that the elephant has a moderately rearranged chromosome complement when compared to humans. The human paint probes identified 53 evolutionary conserved segments on the 27 autosomal elephant chromosomes and the X chromosome. Reciprocal experiments with elephant probes delineated 68 conserved segments in the human genome. The comparison with a recent aardvark and elephant Zoo-FISH study delineates new chromosomal traits which link the two Afrotherian species phylogenetically. In the absence of any morphological evidence the chromosome painting data offer the first non-DNA sequence support for an Afrotherian clade. The comparative human and elephant genome maps provide new insights into the karyotype organization of the proto-afrotherian, the ancestor of extant placental mammals, which most probably consisted of 2n=46 chromosomes.

Animals↗

PubMed2006

Detecting copy number variation in the human genome using comparative genomic hybridization.

Among human beings, it was once estimated that our genomes were 99.9% genetically identical. While this high level of genetic similarity helps to define us as a species, it is our genetic variation that contributes to our phenotypic diversity. As genomic technologies evolve to provide genome-wide analyses at higher resolution, we are beginning to appreciate that the human genome has a lot more variation than was once thought. Array-based comparative genomic hybridization (CGH) is one of these technologies that has recently revealed a newly appreciated type of genetic variation: copy number variation, in which thousands of regions of the human genome are now known to be variable in number between individuals. Some of these copy number variable regions have already been shown to predispose to certain common diseases, and others may ultimately have a significant impact on how each of us reacts to certain foods (e.g., allergic reactions), medications (e.g., pharmacogenomics), microscopic infections (i.e., immunity), and other aspects of our ever-changing environment.

Gene Dosage↗

PubMed2002

Micropapillary serous carcinoma of the ovary has distinct patterns of chromosomal imbalances by comparative genomic hybridization compared with atypical proliferative serous tumors and serous carcinomas.

Recent studies have subdivided serous borderline tumors into 2 categories: atypical proliferative serous tumors (APSTs), which have a relatively benign course, and micropapillary serous carcinomas (MPSCs), which behave like low-grade carcinoma. This study was undertaken to determine, using comparative genomic hybridization (CGH), whether cytogenetic changes support this hypothesis. Nine cases of APST, 10 of MPSC, and 11 of invasive serous carcinoma (SC) were analyzed by CGH. Tumor DNA was extracted from frozen or paraffin-embedded tissue from the primary ovarian tumor, using either sections with at least 70% tumor cells or tissue after relative enrichment by microdissection. Chromosomal imbalances were identified in 3 of 9 APST, 6 of 10 MPSC, and 11 of 11 SC. Three or more chromosomal imbalances were found in 0 of 9 APST, 4 of 10 MPSC, and 9 of 11 SC. Recurrent copy number alterations were grouped into 4 classes correlating with the different tumor types. Class I changes were present in APST and in MPSC or SC and included +8q (7 of 11 SC, 2 of 10 MPSC, 2 of 9 APST), -9p (5 of 11 SC, 0 of 10 MPSC, 1 of 9 APST), and +12 (+12p in 3/11 SC, +12 in 2 of 10 MPSC, +12 in 1 of 9 APST). Class II changes were found only in MPSC and SC, but not in APST. The most frequent examples were +3q (10 of 11 SC, 1 of 10 MPSC), -4q (5 of 11 SC, 1 of 10 MPSC), and -17p (5 of 11 SC, 1 of 10 MPSC). Class III changes were limited to SC, like -16q (7 of 11 SC) and -18q (6 of 11 SC). Class VI changes were unique to MPSC. Gain of 16p (3 of 10 MPSC) was the only aberration in this group. This aberration was not only unique to MPSC but was also the most frequent finding in MPSC. These data support the hypothesis that noninvasive serous tumors of the ovary can be subdivided into 2 categories: APST and MPSC. The number of imbalances in MPSC is substantially higher than in APST and lower than in SC. Some changes in MPSC are shared with SC and APST and others with SC only, suggesting that a subset of MPSC may represent a stage in progression from APST to SC. Other cases of MPSC with independent genetic alterations may represent another subset of tumors that are a distinct entity from APST and SC.

Adolescent↗

PubMed2004

Identification of a novel enhancer of brain expression near the apoE gene cluster by comparative genomics.

Comparative analysis of the human and mouse genomic sequences downstream of the apolipoprotein E gene (APOE) revealed a highly conserved element with previously undefined function. In reporter gene transfection studies, this element which is located approximately 42 kb distal to APOE was found to have silencer activity in a subset of cell lines examined. Analysis of transgenic mice containing a fusion construct linking this distal 631 bp conserved element to a reporter gene comprised of the human APOE gene with its proximal promoter resulted in robust brain expression of the transgenic human apoE mRNA in three independent transgenic lines, supporting the identification of a novel brain controlling region (BCR). Further studies using immunohistochemistry revealed widespread human apoE localization throughout the brains of the BCR-apoE transgenic mice with prominent expression in the cortex and diencephalon. In addition, double-label immunofluorescence performed on brain sections and cultures of primary cortical cells localized human apoE protein to cortical neurons and microglia. These studies demonstrate that comparative sequence analysis is a successful strategy to predict candidate regulatory regions in vivo, although they do not imply that this element controls apoE expression physiologically.

Animals↗

PubMed2005

Comparative genomics using fugu: a tool for the identification of conserved vertebrate cis-regulatory elements.

With the imminent completion of the whole genome sequence of humans, increasing attention is being focused on the annotation of cis-regulatory elements in the human genome. Comparative genomics approaches based on evolutionary conservation have proved useful in the detection of conserved cis-regulatory elements. The pufferfish, Fugu rubripes, is an attractive vertebrate model for comparative genomics, by virtue of its compact genome and maximal phylogenetic distance from mammals. Fugu has lost a large proportion of nonessential DNA, and retained single orthologs for many duplicate genes that arose in the fish lineage. Non-coding sequences conserved between fugu and mammals have been shown to be functional cis-regulatory elements. Thus, fugu is a model fish genome of choice for discovering evolutionarily conserved regulatory elements in the human genome. Such evolutionarily conserved elements are likely to be shared by all vertebrates, and related to regulatory interactions fundamental to all vertebrates. The functions of these conserved vertebrate elements can be rapidly assayed in mammalian cell lines or in transgenic systems such as zebrafish/medaka and Xenopus, followed by validation of crucial elements in transgenic rodents.

Animals↗

PubMed2004

BAC libraries and comparative genomics of aquatic chordate species.

The bacterial artificial chromosome (BAC) system is useful for creating a representation of the genomes of target species. The system is advantageous in that it can accommodate exogenous inserts that are very large (>100 kilobases, kb), thereby allowing entire eukaryotic genes (including flanking regulatory regions) to be encompassed in a single clone. The interest in BACs has recently been spawned by vast improvements in high throughput genomic sequencing such that comparisons of orthologous regions from different genomes (comparative genomics) are being routinely investigated, and comprise a significant component, of all major sequencing centers. In this review, we discuss the general principles of BAC cloning, the resources that are currently available, and some of the applications of the technology. It is not intended to be an exhaustive treatise; rather our goal is to provide a primer of the BAC technology in order to make readers aware of these resources and how they may utilize them in their own research programs.

Animals↗

PubMed2003

The human genome and comparative genomics: understanding human evolution, biology, and medicine.

The entire 2.9-billion-letter sequence (nucleotide base pairs) of the human genome is available as a resource for scientific discovery. Some of the findings from the completion of the human genome were expected, confirming knowledge anticipated by many years of research and analysis in both human and comparative genetics. Other findings were not expected. In either case, the availability of the human genome is likely to have significant implications on basic research, clinical investigation, and ultimately the practice of medicine.

Biological Evolution↗

PubMed1997

Genome screening by comparative genomic hybridization.

Comparative genomic hybridization (CGH) provides a molecular cytogenetic approach for genome-wide scanning of differences in DNA sequence copy number. The technique is now attracting wide-spread interest, especially among cancer researchers. The rapidly expanding database of CGH publications already covers about 1500 tumors and is beginning to reveal genetic abnormalities that are characteristic of certain tumor types or stages of tumor progression. Six novel gene amplifications, as well as a locus for a cancer-predisposition syndrome, have been discovered based on CGH data. CGH has now been established as a first-line screening technique for cancer researchers and will serve as a basis for ongoing efforts to develop high-resolution next-generation genome scanning, such as the microarray technology.

Animals↗

PubMed2006

High throughput sequencing and comparative genomics of foot-and-mouth disease virus.

Despite a basic understanding of many aspects of FMD biology, much information regarding FMDV virulence, host range, and virus transmission remains poorly understood. Here we present how the use of high throughput sequencing for complete genome sequences of foot-and mouth disease virus (FMDV) led to a series of new insights into viral genome sequence conservation and variability, genetic diversity in nature and phylogenetic classification of isolates, including the first complete sequences of the South African Territories type 1 and 3 (SAT1 and SAT3) genomes. Comparative genomic analysis of full-length sequences of FMDV isolates did allow: (i) the identification of highly conserved regulatory or coding regions which are critical for aspects of virus biology as well as novel viral genomic motifs with likely biological relevance; (ii) characterization of the first complete sequences of the SAT1 and SAT3 genomes; (iii) identification of a novel SAT virus lineage genetically distinct from other SAT and Euro-Asiatic lineages; (iv) precise identification of strains circulating around the world for epidemiological and forensic attribution; (v) assessment of mutation and recombination processes as mechanisms equally involved in evolution; (vi) mutation rates, tolerance and constraints of genes and proteins during evolution of FMD viruses during in vivo replication and (vi) support for the hypothesis of a new evolutionary model.

Animals↗

PubMed2006

Ten years of bacterial genome sequencing: comparative-genomics-based discoveries.

It has been more than 10 years since the first bacterial genome sequence was published. Hundreds of bacterial genome sequences are now available for comparative genomics, and searching a given protein against more than a thousand genomes will soon be possible. The subject of this review will address a relatively straightforward question: "What have we learned from this vast amount of new genomic data?" Perhaps one of the most important lessons has been that genetic diversity, at the level of large-scale variation amongst even genomes of the same species, is far greater than was thought. The classical textbook view of evolution relying on the relatively slow accumulation of mutational events at the level of individual bases scattered throughout the genome has changed. One of the most obvious conclusions from examining the sequences from several hundred bacterial genomes is the enormous amount of diversity--even in different genomes from the same bacterial species. This diversity is generated by a variety of mechanisms, including mobile genetic elements and bacteriophages. An examination of the 20 Escherichia coli genomes sequenced so far dramatically illustrates this, with the genome size ranging from 4.6 to 5.5 Mbp; much of the variation appears to be of phage origin. This review also addresses mobile genetic elements, including pathogenicity islands and the structure of transposable elements. There are at least 20 different methods available to compare bacterial genomes. Metagenomics offers the chance to study genomic sequences found in ecosystems, including genomes of species that are difficult to culture. It has become clear that a genome sequence represents more than just a collection of gene sequences for an organism and that information concerning the environment and growth conditions for the organism are important for interpretation of the genomic data. The newly proposed Minimal Information about a Genome Sequence standard has been developed to obtain this information.

Bacterial Vaccines↗

PubMed2004

Use of whole genome amplification and comparative genomic hybridisation to detect chromosomal copy number alterations in cell line material and tumour tissue.

We have established that whole genome amplification (WGA), in conjunction with genomic DNA array comparative genomic hybridisation (gaCGH) allows for the identification of genome-wide copy number abnormalities (CNAs) in DNA extracted from both cell line and patient material. To determine the fidelity and reproducibility of WGA to detect copy number imbalances using gaCGH, well characterized cell line genomic DNA was analysed. The gaCGH data obtained from non-amplified DNA and amplified DNA for the neuroblastoma cell line NUB7 and a paediatric medulloblastoma patient was almost identical. In addition, laser capture microdissection (LCM) of prostate tumour cells and subsequent WGA allowed for the detection of a number of CNAs that may not have been identified if DNA had been extracted in bulk from heterogeneous tissue. The results presented here demonstrate the use of WGA for generating sufficient DNA for gaCGH analysis without the introduction of significant sequence representation bias. The combination of amplification and gaCGH using DNA extracted from archival patient material has the potential for permitting the studying of DNA from small cancerous or pre-cancerous foci, which may help to identify potential genomic markers for early diagnosis.

Cell Line↗