Mark Blaxter

The University of Edinburgh, Edinburgh, Scotland, United Kingdom

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Publications (231)1540.67 Total impact

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    Ben M Sadd, Seth M Barribeau, Guy Bloch, Dirk C de Graaf, Peter Dearden, Christine G Elsik, Jürgen Gadau, Cornelis JP Grimmelikhuijzen, Martin Hasselmann, Jeffrey D Lozier, [......], Daniela Puiu, Jiaxin Qu, Steven L Salzberg, Steven E Scherer, Donna M Muzny, Stephen Richards, Gene E Robinson, Richard A Gibbs, Paul Schmid-Hempel, Kim C Worley
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    Ben M Sadd, Seth M Barribeau, Guy Bloch, Dirk C de Graaf, Peter Dearden, Christine G Elsik, Jürgen Gadau, Cornelis JP Grimmelikhuijzen, Martin Hasselmann, Jeffrey D Lozier, [......], Daniela Puiu, Jiaxin Qu, Steven L Salzberg, Steven E Scherer, Donna M Muzny, Stephen Richards, Gene E Robinson, Richard A Gibbs, Paul Schmid-Hempel, Kim C Worley
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    Ben M Sadd, Seth M Barribeau, Guy Bloch, Dirk C de Graaf, Peter Dearden, Christine G Elsik, Jürgen Gadau, Cornelis JP Grimmelikhuijzen, Martin Hasselmann, Jeffrey D Lozier, [......], Daniela Puiu, Jiaxin Qu, Steven L Salzberg, Steven E Scherer, Donna M Muzny, Stephen Richards, Gene E Robinson, Richard A Gibbs, Paul Schmid-Hempel, Kim C Worley
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    Ben M Sadd, Seth M Barribeau, Guy Bloch, Dirk C de Graaf, Peter Dearden, Christine G Elsik, Jürgen Gadau, Cornelis JP Grimmelikhuijzen, Martin Hasselmann, Jeffrey D Lozier, [......], Daniela Puiu, Jiaxin Qu, Steven L Salzberg, Steven E Scherer, Donna M Muzny, Stephen Richards, Gene E Robinson, Richard A Gibbs, Paul Schmid-Hempel, Kim C Worley
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    B. M. Sadd, S. M. Barribeau, G. Bloch, D. C. de Graaf, P. Dearden, C. G. Elsik, J. Gadau, C. J. Grimmelikhuijzen, M. Hasselmann, J. D. Lozier, [......], D. Puiu, J. Qu, S. L. Salzberg, S. E. Scherer, D. M. Muzny, S. Richards, G. E. Robinson, R. A. Gibbs, P. Schmid-Hempel, K. C. Worley
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    ABSTRACT: Abstract Background The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some species. High- quality genomic data will inform key aspects of bumblebee biology, including susceptibility to implicated population viability threats. Results We report the high quality draft genome sequences of Bombus terrestris and Bombus impatiens, two ecologically dominant bumblebees and widely utilized study species. Comparing these new genomes to those of the highly eusocial honeybee Apis mellifera and other Hymenoptera, we identify deeply conserved similarities, as well as novelties key to the biology of these organisms. Some honeybee genome features thought to underpin advanced eusociality are also present in bumblebees, indicating an earlier evolution in the bee lineage. Xenobiotic detoxification and immune genes are similarly depauperate in bumblebees and honeybees, and multiple categories of genes linked to social organization, including development and behavior, show high conservation. Key differences identified include a bias in bumblebee chemoreception towards gustation from olfaction, and striking differences in microRNAs, potentially responsible for gene regulation underlying social and other traits. Conclusions These two bumblebee genomes provide a foundation for post-genomic research on these key pollinators and insect societies. Overall, gene repertoires suggest that the route to advanced eusociality in bees was mediated by many small changes in many genes and processes, and not by notable expansion or depauperation.
    Genome Biology 04/2015; 16(76). · 10.30 Impact Factor
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    Ben M Sadd, Seth M Barribeau, Guy Bloch, Dirk C de Graaf, Peter Dearden, Christine G Elsik, Jürgen Gadau, Cornelis JP Grimmelikhuijzen, Martin Hasselmann, Jeffrey D Lozier, [......], Daniela Puiu, Jiaxin Qu, Steven L Salzberg, Steven E Scherer, Donna M Muzny, Stephen Richards, Gene E Robinson, Richard A Gibbs, Paul Schmid-Hempel, Kim C Worley
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    ABSTRACT: The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some species. Highquality genomic data will inform key aspects of bumblebee biology, including susceptibility to implicated population viability threats. We report the high quality draft genome sequences of Bombus terrestris and Bombus impatiens, two ecologically dominant bumblebees and widely utilized study species. Comparing these new genomes to those of the highly eusocial honeybee Apis mellifera and other Hymenoptera, we identify deeply conserved similarities, as well as novelties key to the biology of these organisms. Some honeybee genome features thought to underpin advanced eusociality are also present in bumblebees, indicating an earlier evolution in the bee lineage. Xenobiotic detoxification and immune genes are similarly depauperate in bumblebees and honeybees, and multiple categories of genes linked to social organization, including development and behavior, show high conservation. Key differences identified include a bias in bumblebee chemoreception towards gustation from olfaction, and striking differences in microRNAs, potentially responsible for gene regulation underlying social and other traits. These two bumblebee genomes provide a foundation for post-genomic research on these key pollinators and insect societies. Overall, gene repertoires suggest that the route to advanced eusociality in bees was mediated by many small changes in many genes and processes, and not by notable expansion or depauperation.
    Genome Biology 04/2015; 16:76. DOI:10.1186/s13059-015-0623-3 · 10.30 Impact Factor
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    ABSTRACT: Small RNA pathways act at the front line of defence against transposable elements across the Eukaryota. In animals, Piwi interacting small RNAs (piRNAs) are a crucial arm of this defence. However, the evolutionary relationships among piRNAs and other small RNA pathways targeting transposable elements are poorly resolved. To address this question we sequenced small RNAs from multiple, diverse nematode species, producing the first phylum-wide analysis of how small RNA pathways evolve. Surprisingly, despite their prominence in Caenorhabditis elegans and closely related nematodes, piRNAs are absent in all other nematode lineages. We found that there are at least two evolutionarily distinct mechanisms that compensate for the absence of piRNAs, both involving RNA-dependent RNA polymerases (RdRPs). Whilst one pathway is unique to nematodes, the second involves Dicer-dependent RNA-directed DNA methylation, hitherto unknown in animals, and bears striking similarity to transposon-control mechanisms in fungi and plants. Our results highlight the rapid, context-dependent evolution of small RNA pathways and suggest piRNAs in animals may have replaced an ancient eukaryotic RNA-dependent RNA polymerase pathway to control transposable elements.
    PLoS Biology 02/2015; 13(2):e1002061. DOI:10.1371/journal.pbio.1002061 · 11.77 Impact Factor
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    ABSTRACT: Anguillicola crassus is a swim bladder nematode of eels. The parasite is native to the Asian eel Anguilla japonica, but was introduced to Europe and the European eel Anguilla anguilla in the early 1980s. A Taiwanese source has been proposed for this introduction. In the new host in the recipient area, the parasite appears to be more pathogenic. As a reason for these differences, genetically fixed differences in infectivity and development between Taiwanese and European A.crassus have been described and disentangled from plasticity induced by different host environments. To explore whether transcriptional regulation is involved in these lifecycle differences, we have analysed a "common garden", cross infection experiment, using deep-sequencing transcriptomics. Surprisingly, in the face of clear phenotypic differences in life history traits, we identified no significant differences in gene expression between parasite populations or between experimental host species. From 120,000 SNPs identified in the transcriptome data we found that European A. crassus were not a genetic subset of the Taiwanese nematodes sampled. The loci that have the major contribution to the European-Taiwanese population differentiation show an enrichment of synonymous and non-coding polymorphism. This argues against positive selection in population differentiation. However, genes involved in protein processing in the endoplasmatic reticulum membrane and genes bearing secretion signal sequences were enriched in the set of genes most differentiated between European and Taiwanese A. crassus. These genes could be a source for the phenotypically visible genetically fixed differences between European and Taiwanese A. crassus.
    11/2014; 2:e684. DOI:10.7717/peerj.684
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    ABSTRACT: In mammalian systems RNA can move between cells via vesicles. Here we demonstrate that the gastrointestinal nematode Heligmosomoides polygyrus, which infects mice, secretes vesi-cles containing microRNAs (miRNAs) and Y RNAs as well as a nematode Argonaute protein. These vesicles are of intestinal origin and are enriched for homologues of mammalian exo-some proteins. Administration of the nematode exosomes to mice suppresses Type 2 innate responses and eosinophilia induced by the allergen Alternaria. Microarray analysis of mouse cells incubated with nematode exosomes in vitro identifies Il33r and Dusp1 as suppressed genes, and Dusp1 can be repressed by nematode miRNAs based on a reporter assay. We further identify miRNAs from the filarial nematode Litomosoides sigmodontis in the serum of infected mice, suggesting that miRNA secretion into host tissues is conserved among parasitic nematodes. These results reveal exosomes as another mechanism by which helminths manipulate their hosts and provide a mechanistic framework for RNA transfer between animal species.
    Nature Communications 11/2014; 5(5488). DOI:10.1038/ncomms6488 · 10.74 Impact Factor
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    ABSTRACT: The Oxford Nanopore MinION device represents a unique sequencing technology. As a mobile sequencing device powered by the USB port of a laptop, the MinION has huge potential applications. To enable these applications, the bioinformatics community will need to design and build a suite of tools specifically for MinION data.
    Bioinformatics 08/2014; DOI:10.1093/bioinformatics/btu590 · 4.62 Impact Factor
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    Mark Blaxter, Georgios Koutsovoulos
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    ABSTRACT: SUMMARY Nematodes are abundant and diverse, and include many parasitic species. Molecular phylogenetic analyses have shown that parasitism of plants and animals has arisen at least 15 times independently. Extant nematode species also display lifestyles that are proposed to be on the evolutionary trajectory to parasitism. Recent advances have permitted the determination of the genomes and transcriptomes of many nematode species. These new data can be used to further resolve the phylogeny of Nematoda, and identify possible genetic patterns associated with parasitism. Plant-parasitic nematode genomes show evidence of horizontal gene transfer from other members of the rhizosphere, and these genes play important roles in the parasite-host interface. Similar horizontal transfer is not evident in animal parasitic groups. Many nematodes have bacterial symbionts that can be essential for survival. Horizontal transfer from symbionts to the nematode is also common, but its biological importance is unclear. Over 100 nematode species are currently targeted for sequencing, and these data will yield important insights into the biology and evolutionary history of parasitism. It is important that these new technologies are also applied to free-living taxa, so that the pre-parasitic ground state can be inferred, and the novelties associated with parasitism isolated.
    Parasitology 06/2014; 142(S1):1-14. DOI:10.1017/S0031182014000791 · 2.35 Impact Factor
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    ABSTRACT: Filarial nematodes (superfamily Filarioidea) are responsible for an annual global health burden of approximately 6.3 million disability-adjusted life-years, which represents the greatest single component of morbidity attributable to helminths affecting humans. No vaccine exists for the major filarial diseases, lymphatic filariasis and onchocerciasis; in part because research on protective immunity against filariae has been constrained by the inability of the human parasitic species to complete their lifecycles in laboratory mice. However, the rodent filaria Litomosoides sigmodontis has become a popular experimental model, as BALB/c mice are fully permissive for its development and reproduction. Here, we provide a comprehensive analysis of excretory-secretory products from L. sigmodontis across five lifecycle stages and identifications of host proteins associated with first-stage larvae (microfilariae) in the blood. Applying intensity-based quantification, we determined the abundance of 302 unique excretory-secretory proteins, of which 64.6% were present in quantifiable amounts only from gravid adult female nematodes. This lifecycle stage, together with immature microfilariae, released four proteins that have not previously been evaluated as vaccine candidates: a predicted 28.5 kDa filaria-specific protein, a zonadhesin and SCO-spondin-like protein, a vitellogenin, and a protein containing six metridin-like ShK toxin domains. Female nematodes also released two proteins derived from the obligate Wolbachia symbiont. Notably, excretory-secretory products from all parasite stages contained several uncharacterised members of the transthyretin-like protein family. Furthermore, biotin labelling revealed that redox proteins and enzymes involved in purinergic signalling were enriched on the adult nematode cuticle. Comparison of the L. sigmodontis adult secretome with that of the human-infective filarial nematode Brugia malayi (reported previously in three independent published studies) identified differences that suggest a considerable underlying diversity of potential immunomodulators. The molecules identified in L. sigmodontis excretory-secretory products show promise not only for vaccination against filarial infections, but for the amelioration of allergy and autoimmune diseases.
    Molecular &amp Cellular Proteomics 06/2014; 13:2527–2544. DOI:10.1074/mcp.M114.038539 · 7.25 Impact Factor
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    ABSTRACT: Wolbachia are common endosymbionts of terrestrial arthropods, and are also found in nematodes: the animal-parasitic filaria, and the plant-parasite Radopholus similis. Lateral transfer of Wolbachia DNA to the host genome is common. We generated a draft genome sequence for the strongyloidean nematode parasite Dictyocaulus viviparus, the cattle lungworm. In the assembly, we identified nearly 1 Mb of sequence with similarity to Wolbachia. The fragments were unlikely to derive from a live Wolbachia infection: most were short, and the genes were disabled through inactivating mutations. Many fragments were co-assembled with definitively nematode-derived sequence. We found limited evidence of expression of the Wolbachia-derived genes. The D. viviparus Wolbachia genes were most similar to filarial strains and strains from the host-promiscuous clade F. We conclude that D. viviparus was infected by Wolbachia in the past, and that clade F-like symbionts may have been the source of filarial Wolbachia infections.
    PLoS Genetics 06/2014; 10(6):e1004397. DOI:10.1371/journal.pgen.1004397 · 8.17 Impact Factor
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    ABSTRACT: Transposable elements can be categorised into DNA and RNA elements based on their mechanism of transposition. Tyrosine recombinase elements (YREs) are relatively rare and poorly understood, despite sharing characteristics with both DNA and RNA elements. Previously, the Nematoda have been reported to have a substantially different diversity of YREs compared to other animal phyla: the Dirs1-like YRE retrotransposon was encountered in most animal phyla but not in Nematoda, and a unique Pat1-like YRE retrotransposon has only been recorded from Nematoda. We explored the diversity of YREs in Nematoda by sampling broadly across the phylum and including 34 genomes representing the three classes within Nematoda. We developed a method to isolate and classify YREs based on both feature organization and phylogenetic relationships in an open and reproducible workflow. We also ensured that our phylogenetic approach to YRE classification identified truncated and degenerate elements, informatively increasing the number of elements sampled. We identified Dirs1-like elements (thought to be absent from Nematoda) in the nematode classes Enoplia and Dorylaimia indicating that nematode model species do not adequately represent the diversity of transposable elements in the phylum. Nematode Pat1-like elements were found to be a derived form of another PAT element that is present more widely in animals. Several sequence features used widely for the classification of YREs were found to be homoplasious, highlighting the need for a phylogenetically-based classification scheme. Nematode model species do not represent the diversity of transposable elements in the phylum.
    PLoS ONE 04/2014; 9(9). DOI:10.1371/journal.pone.0106630 · 3.53 Impact Factor
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    Proceedings of the Royal Society B: Biological Sciences 03/2014; 281(1783):20133076. DOI:10.1098/rspb.2013.3076 · 5.29 Impact Factor
  • Mark Blaxter
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    ABSTRACT: The handover from maternal to zygotic control has to be carefully orchestrated. In most animal embryos, maternal products drive early embryogenesis, and the genome of the zygote is only switched on later. However, in the nematode Ascaris the zygotic genome is never silent, and the maternal products are rapidly eliminated.
    Current biology: CB 01/2014; 24(2):R72-5. DOI:10.1016/j.cub.2013.11.051 · 9.92 Impact Factor
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    ABSTRACT: The early animal embryo is entirely reliant on maternal gene products for a 'jump-start' that transforms a transcriptionally inactive embryo into a fully functioning zygote. Despite extensive work on model species, it has not been possible to perform a comprehensive comparison of maternally-provisioned transcripts across the Bilateria because of the absence of a suitable dataset from the Lophotrochozoa. As part of an ongoing effort to identify the maternal gene that determines left-right asymmetry in snails, we have generated transcriptome data from 1 to 2-cell and ~32-cell pond snail (Lymnaea stagnalis) embryos. Here, we compare these data to maternal transcript datasets from other bilaterian metazoan groups, including representatives of the Ecydysozoa and Deuterostomia. We found that between 5 and 10% of all L. stagnalis maternal transcripts (~300-400 genes) are also present in the equivalent arthropod (Drosophila melanogaster), nematode (Caenorhabditis elegans), urochordate (Ciona intestinalis) and chordate (Homo sapiens, Mus musculus, Danio rerio) datasets. While the majority of these conserved maternal transcripts ("COMATs") have housekeeping gene functions, they are a non-random subset of all housekeeping genes, with an overrepresentation of functions associated with nucleotide binding, protein degradation and activities associated with the cell cycle. We conclude that a conserved set of maternal transcripts and their associated functions may be a necessary starting point of early development in the Bilateria. For the wider community interested in discovering conservation of gene expression in early bilaterian development, the list of putative COMATs may be useful resource.
    The International Journal of Developmental Biology 01/2014; 58(6-7-8). DOI:10.1387/ijdb.140121ad · 2.57 Impact Factor
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    ABSTRACT: Next-generation sequencing (NGS) technologies have dramatically expanded the breadth of genomics. Genome-scale data, once restricted to a small number of biomedical model organisms, can now be generated for virtually any species at remarkable speed and low cost. Yet non-model organisms often lack a suitable reference to map sequence reads against, making alignment-based quality control (QC) of NGS data more challenging than cases where a well-assembled genome is already available. Here we show that by generating a rapid, non-optimized draft assembly of raw reads, it is possible to obtain reliable and informative QC metrics, thus removing the need for a high quality reference. We use benchmark datasets generated from control samples across a range of genome sizes to illustrate that QC inferences made using draft assemblies are broadly equivalent to those made using a well-established reference, and describe QC tools routinely used in our production facility to assess the quality of NGS data from non-model organisms.
    Frontiers in Genetics 01/2014; 5:111. DOI:10.3389/fgene.2014.00111

Publication Stats

11k Citations
1,540.67 Total Impact Points

Institutions

  • 1996–2015
    • The University of Edinburgh
      • • Institute of Evolutionary Biology
      • • School of Biological Sciences
      • • Ashworth Laboratory
      • • Institute of Cell Biology
      Edinburgh, Scotland, United Kingdom
  • 2012
    • University of Liverpool
      • Institute of Integrative Biology
      Liverpool, England, United Kingdom
    • University College London
      • Department of Genetics, Evolution and Environment (GEE)
      London, ENG, United Kingdom
  • 2011
    • University of Manitoba
      Winnipeg, Manitoba, Canada
    • University of Cologne
      • Zoological Institute
      Köln, North Rhine-Westphalia, Germany
  • 2000–2010
    • University of Nottingham
      • • Centre for Sports Medicine
      • • School of Life Sciences
      Nottingham, ENG, United Kingdom
    • Simon Fraser University
      • Department of Biological Sciences
      Burnaby, British Columbia, Canada
  • 2009
    • SickKids
      • Program in Molecular Structure and Function
      Toronto, Ontario, Canada
    • University of Leicester
      • Department of Biochemistry
      Leicester, ENG, United Kingdom
  • 2006
    • University of California, Riverside
      Riverside, California, United States
  • 2005
    • University of Toronto
      • Hospital for Sick Children
      Toronto, Ontario, Canada
  • 1996–1999
    • University of Antwerp
      Antwerpen, Flanders, Belgium
  • 1990–1995
    • Imperial College London
      • Division of Cell and Molecular Biology
      Londinium, England, United Kingdom
  • 1994
    • University of Otago
      • Department of Biochemistry
      Taieri, Otago, New Zealand