Biomedical subjects

Jane Carlton

Publications and source records attributed to Jane Carlton.

8 recordsLinked to original sources

PubMed2005

Comparative genomics of malaria parasites.

In the past few years, the area of comparative genomics of malaria parasites has begun to come of age, with the completion of genome sequencing projects of four Plasmodium species, and several functional genomics studies. A picture is emerging of a parasite genome that is highly adapted to its mammalian and vector hosts, and which uses post-transcriptional gene-silencing as one method for the control of gene expression. The genome is compartmentalized into a core of conserved housekeeping genes, sandwiched between subtelomerically located genes encoding surface antigens. Species-specific gene families shape the preference of the parasite for host cells, in addition to determining interactions with the host immune-system. Recent research has led to the description of a motif that is conserved across Plasmodium species and which plays a central role in protein export into the host cell.

Animals↗

PubMed2005

Host switch leads to emergence of Plasmodium vivax malaria in humans.

The geographical origin of Plasmodium vivax, the most widespread human malaria parasite, is controversial. Although genetic closeness to Asian primate malarias has been confirmed by phylogenetic analyses, genetic similarities between P. vivax and Plasmodium simium, a New World primate malaria, suggest that humans may have acquired P. vivax from New World monkeys or vice versa. Additionally, the near fixation of the Duffy-negative blood type (FY x B(null)/FY x B(null)) in West and Central Africa, consistent with directional selection, and the association of Duffy negativity with complete resistance to vivax malaria suggest a prolonged period of host-parasite coevolution in Africa. Here we use Bayesian and likelihood methods in conjunction with cophylogeny mapping to reconstruct the genetic and coevolutionary history of P. vivax from the complete mitochondrial genome of 176 isolates as well as several closely related Plasmodium species. Taken together, a haplotype network, parasite migration patterns, demographic history, and cophylogeny mapping support an Asian origin via a host switch from macaque monkeys.

Animals↗

PubMed2005

The genome of model malaria parasites, and comparative genomics.

The field of comparative genomics of malaria parasites has recently come of age with the completion of the whole genome sequences of the human malaria parasite Plasmodium falciparum and a rodent malaria model, Plasmodium yoelii yoelii. With several other genome sequencing projects of different model and human malaria parasite species underway, comparing genomes from multiple species has necessitated the development of improved informatics tools and analyses. Results from initial comparative analyses reveal striking conservation of gene synteny between malaria species within conserved chromosome cores, in contrast to reduced homology within subtelomeric regions, in line with previous findings on a smaller scale. Genes that elicit a host immune response are frequently found to be species-specific, although a large variant multigene family is common to many rodent malaria species and Plasmodium vivax. Sequence alignment of syntenic regions from multiple species has revealed the similarity between species in coding regions to be high relative to non-coding regions, and phylogenetic footprinting studies promise to reveal conserved motifs in the latter. Comparison of non-synonymous substitution rates between orthologous genes is proving a powerful technique for identifying genes under selection pressure, and may be useful for vaccine design. This is a stimulating time for comparative genomics of model and human malaria parasites, which promises to produce useful results for the development of antimalarial drugs and vaccines.

Animals↗

PubMed2004

Genome sequence of Silicibacter pomeroyi reveals adaptations to the marine environment.

Since the recognition of prokaryotes as essential components of the oceanic food web, bacterioplankton have been acknowledged as catalysts of most major biogeochemical processes in the sea. Studying heterotrophic bacterioplankton has been challenging, however, as most major clades have never been cultured or have only been grown to low densities in sea water. Here we describe the genome sequence of Silicibacter pomeroyi, a member of the marine Roseobacter clade (Fig. 1), the relatives of which comprise approximately 10-20% of coastal and oceanic mixed-layer bacterioplankton. This first genome sequence from any major heterotrophic clade consists of a chromosome (4,109,442 base pairs) and megaplasmid (491,611 base pairs). Genome analysis indicates that this organism relies upon a lithoheterotrophic strategy that uses inorganic compounds (carbon monoxide and sulphide) to supplement heterotrophy. Silicibacter pomeroyi also has genes advantageous for associations with plankton and suspended particles, including genes for uptake of algal-derived compounds, use of metabolites from reducing microzones, rapid growth and cell-density-dependent regulation. This bacterium has a physiology distinct from that of marine oligotrophs, adding a new strategy to the recognized repertoire for coping with a nutrient-poor ocean.

Adaptation, Physiological↗

PubMed2004

Gene synteny and chloroquine resistance in Plasmodium chabaudi.

Chloroquine resistance in the rodent malaria parasite Plasmodium chabaudi has been shown to be caused by a gene on chromosome 11, and is not linked to orthologues of the Plasmodium falciparum chloroquine resistance transporter (pfcrt) or Pgh-1 (pfmdr1) genes. In the current work, the progeny of crosses between chloroquine-resistant and sensitive clones of P. chabaudi have been analysed for the inheritance of 658 AFLP markers. Markers linked to the chloroquine responses of the progeny, including two which are completely linked, have been genetically mapped, sequenced and their homologues, or closely linked loci, identified in P. falciparum. The chromosome 11 markers most closely linked to chloroquine resistance in P. chabaudi map to loci which are also closely linked in P. falciparum, although in two linkage groups on chromosomes 6 and 13 of this species. The P. falciparum orthologue of the gene conferring chloroquine resistance in P. chabaudi is predicted to lie within a 250 kb region of P. falciparum chromosome 6, containing approximately 50 genes. The genetic order of the markers in P. chabaudi is co-linear with the physical linkage represented in the P. falciparum genome database. The findings provide evidence for extensive conservation of synteny between the two species.

Animals↗

PubMed2003

The Plasmodium vivax genome sequencing project.

With the successful completion of the project to sequence the Plasmodium falciparum genome, researchers are now turning their attention to other malaria parasite species. Here, an update on the Plasmodium vivax genome sequencing project is presented, as part of the Trends in Parasitology series of reviews expanding on various aspects of P. vivax research.

Animals↗

PubMed2002

Fast algorithms for large-scale genome alignment and comparison.

We describe a suffix-tree algorithm that can align the entire genome sequences of eukaryotic and prokaryotic organisms with minimal use of computer time and memory. The new system, MUMmer 2, runs three times faster while using one-third as much memory as the original MUMmer system. It has been used successfully to align the entire human and mouse genomes to each other, and to align numerous smaller eukaryotic and prokaryotic genomes. A new module permits the alignment of multiple DNA sequence fragments, which has proven valuable in the comparison of incomplete genome sequences. We also describe a method to align more distantly related genomes by detecting protein sequence homology. This extension to MUMmer aligns two genomes after translating the sequence in all six reading frames, extracts all matching protein sequences and then clusters together matches. This method has been applied to both incomplete and complete genome sequences in order to detect regions of conserved synteny, in which multiple proteins from one organism are found in the same order and orientation in another. The system code is being made freely available by the authors.

Algorithms↗

PubMed2002

The shikimate pathway and its branches in apicomplexan parasites.

The shikimate pathway is essential for production of a plethora of aromatic compounds in plants, bacteria, and fungi. Seven enzymes of the shikimate pathway catalyze sequential conversion of erythrose 4-phosphate and phosphoenol pyruvate to chorismate. Chorismate is then used as a substrate for other pathways that culminate in production of folates, ubiquinone, napthoquinones, and the aromatic amino acids tryptophan, phenylalanine, and tyrosine. The shikimate pathway is absent from animals and present in the apicomplexan parasites Toxoplasma gondii, Plasmodium falciparum, and Cryptosporidium parvum. Inhibition of the pathway by glyphosate is effective in controlling growth of these parasites. These findings emphasize the potential benefits of developing additional effective inhibitors of the shikimate pathway. Such inhibitors may function as broad-spectrum antimicrobial agents that are effective against bacterial and fungal pathogens and apicomplexan parasites.

Amino Acid Sequence↗