Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Genome evolution”

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 1,027 records · Page 57Linked to original sources
PubMed2006

Comparison of Pax1/9 locus reveals 500-Myr-old syntenic block and evolutionary conserved noncoding regions.

Identification of conserved genomic regions within and between different genomes is crucial when studying genome evolution. Here, we described regions of strong synteny conservation between vertebrate deuterostomes (tetrapods and teleosts) and invertebrate deuterostomes (amphioxus and sea urchin). The shared gene contents across phylogenetically distant species demonstrate that the conservation of the regions stemmed from an ancestral segment instead of a series of independent convergent events. Comparison of the syntenic regions allows us to postulate the primitive gene organization in the last common ancestor of deuterostomes and the evolutionary events that occurred to the 3 distinct lineages of sea urchin, amphioxus, and vertebrates after their separation. In addition, alignment of the syntenic regions led to the identification of 8 noncoding evolutionarily conserved regions shared between amphioxus and vertebrates. To our knowledge, this is the first report of conserved noncoding sequences shared by vertebrates and nonvertebrates. These noncoding sequences have high possibility of being elements that regulate neighboring genes. They are likely to be a factor in the maintenance of conserved synteny over long phylogenetic distance in different deuterostome lineages.

Amino Acid Sequence↗
PubMed1987

Translocation and amplification of an X-chromosome DNA repeat in inbred strains of mice.

A 9-kb repetitive DNA fragment (70-38) located near the centromere of the mouse X chromosome is amplified and translocated to an autosome in different inbred strains of mice. In situ hybridization and hybrid cell studies showed that probe 70-38 is located only on the X chromosome in mouse strains A/J, AKR/J, BALB/cJ, CBA/J, C3H/HeJ, C57BL/6J, DBA/2J and SWR/J. However, in four other mouse strains the DNA sequence is found near the centromere of an autosome in addition to the X chromosome. This autosome differs among the mouse strains (chromosome 11 in C57BL/10J or ScSn, chromosome 13 in NZB/B1NJ and chromosome 17 in SJL/J and PO). In those strains where the repeated sequence is located on an autosome, it has been amplified to about 100 copies. Restriction enzyme digestion patterns suggest a common structure for 70-38 sequences in the different strains. The changes in copy number, restriction enzyme digestion patterns, and chromosomal location of 70-38 reflect a rapid genomic evolution inbred mouse strains.

Animals↗
PubMed1987

Polymorphisms on the right arm of yeast chromosome III associated with Ty transposition and recombination events.

The region of Saccharomyces cerevisiae chromosome III centromere-distal to the PGK gene is the site of frequent chromosome polymorphisms. We have sequenced this region from fragments of chromosome III isolated from three different yeast strains, GRF88, CN31C and CF4-16B. The sequence analysis demonstrates that these polymorphisms are associated with the presence of Ty and delta elements and defines a region of the chromosome which is a hot-spot for transposition events (the RAHS). The three strains can be arranged into a logical evolutionary series in which successive transposition and recombination events insert Ty elements and fuse them with consequent deletions of chromosome and of transposon sequences. The influence of such events on yeast genome evolution is discussed.

Base Sequence↗
PubMed1997

IMGT, the international ImMunoGeneTics database.

IMGT, the international ImMunoGeneTics database, is an integrated database specializing in immunoglobulins, T-cell receptors (TcR) and major histocompatibility complex (MHC) of all vertebrate species, initiated and co-ordinated by Marie-Paule Lefranc, CNRS, Montpellier II University, Montpellier, France (lefranc@ligm.crbm.cnrs-mop.fr). IMGT includes two databases: LIGM-DB (for immunoglobulins and TcR) and MHC/HLA-DB. IMGT comprises expertly annotated sequences and alignment tables. LIGM-DB contains more than 19 000 immunoglobulin and TcR sequences from 78 species. MHC/HLA-DB contains class I and class II human leukocyte antigen alignment tables. An IMGT tool, DNAPLOT, developed for immunoglobulins, TcR and MHC sequence alignments, is also available. IMGT works in close collaboration with the EMBL database. IMGT goals are to establish a common data access to all immunogenetics data, including sequences, oligonucleotide primers, gene maps and other genetic data of immunoglobulins, TcR and MHC molecules, and to provide a graphical user-friendly data access. IMGT will have important implications in medical research (repertoire in autoimmune diseases, AIDS, leukemias, lymphomas), therapeutical approaches (antibody engineering), genome diversity and genome evolution studies. IMGT can be accessed at http://imgt.cnusc.fr:8104 and http://www.ebi.ac.uk/IMGT

Amino Acid Sequence↗
PubMed1998

IMGT, the International ImMunoGeneTics database.

IMGT, the international ImMunoGeneTics database, is an integrated database specialising in Immunoglobulins (Ig), T cell Receptors (TcR) and Major Histocompatibility Complex (MHC) of all vertebrate species, created by Marie-Paule Lefranc, CNRS, Montpellier II University, Montpellier, France (lefranc@ligm.crbm.cnrs-mop.fr). IMGT includes three databases: LIGM-DB (for Ig and TcR), MHC/HLA-DB and PRIMER-DB (the last two in development). IMGT comprises expertly annotated sequences and alignment tables. LIGM-DB contains more than 23 000 Immunoglobulin and T cell Receptor sequences from 78 species. MHC/HLA-DB contains Class I and Class II Human Leucocyte Antigen alignment tables. An IMGT tool, DNAPLOT, developed for Ig, TcR and MHC sequence alignments, is also available. IMGT works in close collaboration with the EMBL database. IMGT goals are to establish a common data access to all immunogenetics data, including nucleotide and protein sequences, oligonucleotide primers, gene maps and other genetic data of Ig, TcR and MHC molecules, and to provide a graphical user friendly data access. IMGT has important implications in medical research (repertoire in autoimmune diseases, AIDS, leukemias, lymphomas), therapeutical approaches (antibody engineering), genome diversity and genome evolution studies. IMGT is freely available at http://imgt.cnusc.fr:8104

Amino Acid Sequence↗
PubMed1999

IMGT, the international ImMunoGeneTics database.

IMGT, the international ImMunoGeneTics database (http://imgt.cnusc. fr:8104), is a high-quality integrated database specialising in Immunoglobulins (Ig), T cell Receptors (TcR) and Major Histocompatibility Complex (MHC) molecules of all vertebrate species, created in 1989 by Marie-Paule Lefranc, Université Montpellier II, CNRS, Montpellier, France (lefranc@ligm.igh.cnrs.fr). IMGT comprises three databases: LIGM-DB, a comprehensive database of Ig and TcR, MHC/HLA-DB, and PRIMER-DB (the last two in development); a tool, IMGT/DNAPLOT, developed for sequence analysis and alignments; and expertised data based on the IMGT scientific chart, the IMGT repertoire. By its high quality and its easy data distribution, IMGT has important implications in medical research (repertoire in autoimmune diseases, AIDS, leukemias, lymphomas), therapeutic approaches (antibody engineering), genome diversity and genome evolution studies. IMGT is freely available at http://imgt.cnusc. fr:8104

Animals↗
PubMed1999

Animal mitochondrial genomes.

Animal mitochondrial DNA is a small, extrachromosomal genome, typically approximately 16 kb in size. With few exceptions, all animal mitochondrial genomes contain the same 37 genes: two for rRNAs, 13 for proteins and 22 for tRNAs. The products of these genes, along with RNAs and proteins imported from the cytoplasm, endow mitochondria with their own systems for DNA replication, transcription, mRNA processing and translation of proteins. The study of these genomes as they function in mitochondrial systems-'mitochondrial genomics'-serves as a model for genome evolution. Furthermore, the comparison of animal mitochondrial gene arrangements has become a very powerful means for inferring ancient evolutionary relationships, since rearrangements appear to be unique, generally rare events that are unlikely to arise independently in separate evolutionary lineages. Complete mitochondrial gene arrangements have been published for 58 chordate species and 29 non-chordate species, and partial arrangements for hundreds of other taxa. This review compares and summarizes these gene arrangements and points out some of the questions that may be addressed by comparing mitochondrial systems.

Animals↗
PubMed2000

IMGT, the international ImMunoGeneTics database.

IMGT, the international ImMunoGeneTics database (http://imgt.cines. fr:8104 ), is a high-quality integrated database specialising in Immunoglobulins (Ig), T cell Receptors (TcR) and Major Histocompatibility Complex (MHC) molecules of all vertebrate species, created in 1989 by Marie-Paule Lefranc, Université Montpellier II, CNRS, Montpellier, France (lefranc@ligm.igh.cnrs.fr ). At present, IMGT includes two databases: IMGT/LIGM-DB, a comprehensive database of Ig and TcR from human and other vertebrates, with translation for fully annotated sequences, and IMGT/HLA-DB, a database of the human MHC referred to as HLA (Human Leucocyte Antigens). The IMGT server provides a common access to expertized genomic, proteomic, structural and polymorphic data of Ig and TcR molecules of all vertebrates. By its high quality and its easy data distribution, IMGT has important implications in medical research (repertoire in autoimmune diseases, AIDS, leukemias, lymphomas), therapeutic approaches (antibody engineering), genome diversity and genome evolution studies. IMGT is freely available at http://imgt.cines.fr:8104. The IMGT Index is provided at the IMGT Marie-Paule page (http://imgt.cines.fr:8104/textes/IMGTindex.html).

Amino Acid Sequence↗
PubMedDate not supplied

Gene mapping in the spider monkey (Ateles paniscus chamek).

Sixteen isozyme markers have been assigned to the chromosome complement of the neotropical primate species Ateles paniscus chamek using three somatic cell hybrid panels. Several genetic associations were found to be common between humans and this species, despite the fact that Ateles is a karyologically rearranged taxon. Conversely, several human gene clusters were disrupted, resulting in gene associations not previously found in other primates. A comparison with other primates and mammalian orders, for which gene maps are available, was carried out for a comprehensive evaluation of genome evolution in these disparate taxa.

Animals↗
PubMed2001

Shared nucleotide composition biases among species and their impact on phylogenetic reconstructions of the Drosophilidae.

Compositional changes are a major feature of genome evolution. Overlooking nucleotide composition differences among sequences can seriously mislead phylogenetic reconstructions. Large compositional variation exists among the members of the family Drosophilidae. Until now, however, base composition differences have been largely neglected in the formulations of the nucleotide substitution process used to reconstruct the phylogeny of this important group of species. The present study adopts a maximum-likelihood framework of phylogenetic inference in order to analyze five nuclear gene regions and shows that (1) the pattern of compositional variation in the Drosophilidae does not match the phylogeny of the species; (2) accounting for the heterogeneous GC content with Galtier and Gouy's nucleotide substitution model leads to a tree that differs in significant aspects from the tree inferred when the nucleotide composition differences are ignored, even though both phylogenetic hypotheses attain strong nodal support in the bootstrap analyses; and (3) the LogDet distance correction cannot completely overcome the distorting effects of the compositional variation that exists among the species of the Drosophilidae. Our analyses confidently place the Chymomyza genus as an outgroup closer than the genus Scaptodrosophila to the Drosophila genus and conclusively support the monophyly of the Sophophora subgenus.

Alcohol Dehydrogenase↗
PubMed2001

CsRn1, a novel active retrotransposon in a parasitic trematode, Clonorchis sinensis, discloses a new phylogenetic clade of Ty3/gypsy-like LTR retrotransposons.

We screened the genome of a trematode, Clonorchis sinensis, in order to identify novel retrotransposons and thereby provide additional information on retrotransposons for comprehensive phylogenetic study. Considering the vast potential of retrotransposons to generate genetically variable regions among individual genomes, randomly amplified polymorphic DNAs (RAPDs) detected by arbitrarily primed polymerase chain reactions were selected as candidates for retrotransposon-related sequences. From RAPD analysis, we isolated and characterized a novel retrotransposon in C. sinensis as the first member of uncorrupted long-terminal-repeat (LTR) retrotransposons in phylum Platyhelminthes. The retrotransposon, which was named Clonorchis sinensis Retrotransposon 1 (CsRn1), showed a genomewide distribution and had a copy number of more than 100 per haploid genome. CsRn1 encoded an uninterrupted open reading frame (ORF) of 1,304 amino acids, and the deduced ORF exhibited similarities to the pol proteins of Ty3/gypsy-like LTR retrotransposons. The mobile activity of master copies was predicted by sequence analysis and confirmed by the presence of mRNA transcripts. Phylogenetic analysis of Ty3/gypsy-like LTR retrotransposons detected a new clade comprising CsRn1, Kabuki of Bombyx mori, and an uncharacterized element of Drosophila melanogaster. With its high repetitiveness and preserved mobile activity, it is proposed that CsRn1 may play a significant role in the genomic evolution of C. sinensis.

Amino Acid Sequence↗
PubMed1999

The non-LTR retrotransposon Rex3 from the fish Xiphophorus is widespread among teleosts.

Rex3, the first reverse transcriptase (RT)-encoding retrotransposon isolated from the melanoma fish model Xiphophorus, is a non-long-terminal-repeat element related to the RTE family. The essential features of Rex3 are (1) an endonuclease and a reverse transcriptase, (2) 5' truncations of most of the copies, (3) a 3' tail consisting of tandem repeats of the sequence GATG, and (4) short target site sequence duplications of variable length. Compilation of Rex3 sequences from the pufferfish genome project suggested that, as observed for other members of the RTE family, no additional large open reading frame was present upstream of the endonuclease/reverse transcriptase open reading frame. There are about a thousand copies of Rex3 in the haploid genome of Xiphophorus, some of them probably resulting from recent retrotransposition events. Rex3 RNA was detected by RT-PCR in melanoma and in nontumorous tissues, as well as in melanoma-derived and embryonic cell lines. Rex3 is present in a broad panel of teleost species and was found in the promoter region and in introns of various genes. To our knowledge, Rex3 is the first autonomous retrotransposon described to date which is widespread in teleosts. This wide distribution and occasional association with coding sequences may confer on Rex3 a predisposition to play a role in genome evolution in teleosts.

Amino Acid Sequence↗
PubMed1996

The fibronectin gene as a model for splicing and transcription studies.

The fibronectin (FN) gene has become paradigmatic to illustrate genome evolution by exon shuffling, generation of protein diversity by alternative mRNA splicing, and topological coordination between transcription and splicing. Alternative splicing in three sites of the primary transcript gives rise to multiple FN polypeptides. This process is cell type-, development- and age-regulated. The different FN variants seem to play specific roles in FN dimer secretion, blood clotting, adhesion to lymphoid cells, skin wound healing, atherosclerosis, and liver fibrosis. This review focuses on function assignment to the alternatively spliced segments, as well as on the external signals and cis-acting sequences that control the mechanisms of alternative splicing. We also discuss FN transcriptional regulation in response to viral transformation, growth factors, and cyclic AMP in the light of promoter architecture and its interaction with specific transcription factors. The relevance of FN RNA "tracks" as assembly lines of coordinated transcription and RNA processing is also addressed.

Alternative Splicing↗
PubMed1998

A temperature cline in copy number for 412 but not roo/B104 retrotransposons in populations of Drosophila simulans.

The copy number of the retrotransposable element 412 of Drosophila simulans from populations collected worldwide shows a negative correlation with minimum temperature. No association was detected for the roo/B104 element. The possibility that selective pressures might regulate the 412 copy number in these natural populations is supported by detection of selection against the detrimental effects of 412 insertions (estimated by the proportion of insertions on the X chromosome in comparison with the autosomes) but not roo/B104. These data reveal different spatial patterns for two element families, and strongly suggest that some factors in the environment, such as temperature, may interfere with the control of retrotransposition, thus affecting important aspects of genomic evolution.

Animals↗
PubMed2025

Adaptation in a keystone grazer under novel predation pressure.

Understanding how species adapt to environmental change is necessary to protect biodiversity and ecosystem services. Growing evidence suggests species can adapt rapidly to novel selection pressures like predation from invasive species, but the repeatability and predictability of selection remain poorly understood in wild populations. We tested how a keystone aquatic herbivore, Daphnia pulicaria, evolved in response to predation pressure by the introduced zooplanktivore Bythotrephes longimanus. Using high-resolution 210Pb-dated sediment cores from 12 lakes in Ontario (Canada), which primarily differed in invasion status by Bythotrephes, we compared Daphnia population genetic structure over time using whole-genome sequencing of individual resting embryos. We found strong genetic differentiation between populations approximately 70 years before versus 30 years after reported Bythotrephes invasion, with no difference over this period in uninvaded lakes. Compared with uninvaded lakes, we identified, on average, 64 times more loci were putatively under selection in the invaded lakes. Differentiated loci were mainly associated with known reproductive and stress responses, and mean body size consistently increased by 14.1% over time in invaded lakes. These results suggest Daphnia populations were repeatedly acquiring heritable genetic adaptations to escape gape-limited predation. More generally, our results suggest some aspects of environmental change predictably shape genome evolution.

Animals↗
PubMed2006

Patterns and mechanisms of genetic and phenotypic differentiation in marine microbes.

Microbes in the ocean dominate biogeochemical processes and are far more diverse than anticipated. Thus, in order to understand the ocean system, we need to delineate microbial populations with predictable ecological functions. Recent observations suggest that ocean communities comprise diverse groups of bacteria organized into genotypic (and phenotypic) clusters of closely related organisms. Although such patterns are similar to metazoan communities, the underlying mechanisms for microbial communities may differ substantially. Indeed, the potential among ocean microbes for vast population sizes, extensive migration and both homologous and illegitimate genetic recombinations, which are uncoupled from reproduction, challenges classical population models primarily developed for sexually reproducing animals. We examine possible mechanisms leading to the formation of genotypic clusters and consider alternative population genetic models for differentiation at individual loci as well as gene content at the level of whole genomes. We further suggest that ocean bacteria follow at least two different adaptive strategies, which constrain rates and bounds of evolutionary processes: the 'opportunitroph', exploiting spatially and temporally variable resources; and the passive oligotroph, efficiently using low nutrient concentrations. These ecological lifestyle differences may represent a fundamental divide with major consequences for growth and predation rates, genome evolution and population diversity, as emergent properties driving the division of labour within microbial communities.

Adaptation, Biological↗
PubMed1998

The pnk/pnl gene (ORF 86) of Autographa californica nucleopolyhedrovirus is a non-essential, immediate early gene.

Autographa californica nucleopolyhedrovirus (AcMNPV) ORF 86, located within the HindIII C fragment, potentially encodes a protein which shares sequence similarity with two T4 bacteriophage gene products, RNA ligase and polynucleotide kinase. This AcMNPV gene has been designated pnk/pnl but has yet to be assigned a function in virus replication. It has been classified as an immediate early virus gene, since the promoter was active in uninfected insect cells and mRNA transcripts were detectable from 4 to 48 h post-infection and in the presence of cycloheximide or aphidicolin in virus-infected cells. The extremities of the transcript have been mapped by primer extension and 3' RACE-PCR to positions -18 from the translational start codon and +15 downstream of the stop codon. The function of pnk/pnl was investigated by producing a recombinant virus (Acdel86lacZ) with the coding region replaced with that of lacZ. This virus replicated normally in Spodoptera frugiperda (Sf 21) cells, indicating that pnk/pnl is not essential for propagation in these cells. Virus protein production in Acdel86lacZ-infected Sf 21 cells also appeared to be unaffected, with normal synthesis of the IE-1, GP64, VP39 and polyhedrin proteins. Shut-down of host protein synthesis was not abolished in recombinant infection. When other baculovirus genomes were examined for the presence of pnk/pnl by restriction enzyme digestion and PCR, a deletion was found in AcMNPV 1.2, Galleria mellonella NPV (GmMNPV) and Bombyx mori NPV (BmNPV), suggesting that in many isolates this gene has either never been acquired or has been lost during genome evolution. This is one of the first baculovirus immediate early genes that appears to be nonessential for virus survival.

Amino Acid Sequence↗
PubMed1999

Dynamics of rabies virus quasispecies during serial passages in heterologous hosts.

To understand the mutations and genetic rearrangements that allow rabies virus infections of new hosts and adaptation in nature, the quasispecies structure of the nucleoprotein and glycoprotein genes as well as two noncoding sequences of a rabies virus genome were determined. Gene sequences were obtained from the brain and from the salivary glands of the original host, a naturally infected European fox, and after serial passages in mice, dogs, cats and cell culture. A relative genetic stasis of the consensus sequences confirmed previous results about the stability of rabies virus. At the quasispecies level, the mutation frequency varies, in the following order: glycoprotein region (21.9 x 10(-4) mutations per bp), noncoding sequence nucleoprotein-phosphoprotein region (7.2-7.9 x 10(-4) mutations per bp) and nucleoprotein gene region (2.9-3.7 x 10(-4) mutations per bp). These frequencies varied according to the number, type of heterologous passages and the genomic region considered. The shape of the quasispecies structure was dramatically modified by passages in mice, in which the mutation frequencies increased by 12-31 x 10(-4) mutations per bp, depending on the region considered. Non-synonymous mutations were preponderant particularly in the glycoprotein gene, stressing the importance of positive selection in the maintenance and fixation of substitutions. Two mechanisms of genomic evolution of the rabies virus quasispecies, while adapting to environmental changes, have been identified: a limited accumulation of mutations with no replacement of the original master sequence and a less frequent but rapid selective overgrowth of favoured variants.

Animals↗