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Chris Secombes

Publications and source records attributed to Chris Secombes.

9 recordsLinked to original sources
PubMed2006

Discovery of multiple beta-defensin like homologues in teleost fish.

Using a database mining approach, multiple defensin like genes have been discovered for the first time in fish, in species including zebrafish Danio rerio and the pufferfish, Takifugu rubripes and Tetraodon nigroviridis. They share the common features of vertebrate defensins, including small size, net cationic charge, and six conserved cysteines in the mature region. Based on their cysteine arrangement, the identified fish defensin like peptides resemble beta-defensin family members in birds and mammals. Computing modelling detected three beta-strands in all three zebrafish defensins and an extra N-terminal alpha-helix in one of the peptides. The coding regions of the fish genes contain three exons and two introns, the same as avian defensin genes. In zebrafish and tetraodon, two defensin genes identified are located in the same chromosome. An additional locus containing a third defensin gene has also been found in a different chromosome in zebrafish, demonstrating that multiple defensin loci may be present in fish. Comparative studies suggest that beta-defensins may represent the primitive form of the defensin family, which expanded during evolution by gene or genome duplication. In healthy zebrafish, constitutive expression of defensins was detected by RT-PCR in gill, gonad, gut, kidney, muscle, skin and spleen but the levels and patterns varied for individual defensin genes.

Amino Acid Sequence↗
PubMed2006

Molecular and expression analysis of an interferon-gamma-inducible guanylate-binding protein from rainbow trout (Oncorhynchus mykiss).

Guanylate-binding proteins (GBPs) are some of the most abundant proteins accumulating in mammalian cells in response to interferon-gamma (IFN-gamma). GBPs have been suggested to function in antiviral activity, macrophage activation, fibroblast proliferation and inhibition of endothelial cell proliferation and invasiveness. Here we confirm that IFN-gamma-inducible GBP also exist in fish. A 2 kb GBP cDNA was cloned from head kidney of rainbow trout treated with an IFN-inducing compound. The open reading frame predicts a 635 amino acid protein (rbtGBP) of 72.7 kDa possessing a tripartite GTP binding motif and a secondary structure similar to human GBP1. Like most mammalian GBPs, rbtGBP possesses an isoprenylation motif at the C-terminal end. The overall amino acid sequence identity between rbtGBP and mammalian GBPs is only 41-47%, however. The rainbow trout macrophage cell line RTS11 showed a dose-dependent increase in rbtGBP transcripts in response to IFN-gamma after 6h of stimulation, with rbtGBP being undetectable in non-treated RTS11 cells. Moreover, polyinosinic polycytidylic acid (poly I:C) induced increased GBP transcript levels in RTS11 and RTG2 cells after 4-6 h of stimulation, and in head kidney and liver of live fish after 24 h. These studies suggest that rbtGBP is an early response gene in rainbow trout, which may have similar functions in IFN-gamma mediated responses as mammalian GBPs.

Amino Acid Sequence↗
PubMed2005

Identification and bioactivities of IFN-gamma in rainbow trout Oncorhynchus mykiss: the first Th1-type cytokine characterized functionally in fish.

IFN-gamma is one of the key cytokines in defining Th1 immune responses. In this study, an IFN-gamma homologue has been identified in rainbow trout Oncorhynchus mykiss, and its biological activities have been characterized. The trout IFN-gamma cDNA is 1034 bp in length and translates into a 180-aa protein. The first intron of the trout IFN-gamma gene contains highly polymorphic GACA minisatellites and 44-bp DNA repeats, giving rise to at least six alleles. IFN-gamma is structurally conserved among vertebrates, and a signature motif has been identified. A nuclear localization sequence known to be crucial for IFN-gamma biological activities is also present in the C-terminal region of the trout IFN-gamma. The IFN-gamma expression was induced in head kidney leukocytes by stimulation with PHA or poly(I:C) and in kidney and spleen of fish injected with poly(I:C). rIFN-gamma produced in Escherichia coli significantly stimulated gene expression of IFN-gamma-inducible protein 10 (gammaIP-10), MHC class II beta-chain, and STAT1, and enhanced respiratory burst activity in macrophages. Deletion of 29-aa residues from the C terminus containing the nuclear localization sequence motif resulted in loss of activity with respect to induction of gammaIP-10 in RTS-11 cells. Moreover, IFN-gamma-induced gammaIP-10 expression was completely abolished by the protein kinase C inhibitor staurosporine, and partially reduced by U0126, a specific inhibitor for ERKs. Taken together, the present study has demonstrated for the first time a functional IFN-gamma homologue in a fish species, strongly suggesting a conserved Th1 immune response is most likely present in lower vertebrates.

Amino Acid Sequence↗
PubMed2005

Characterisation and expression analysis of an interleukin 6 homologue in the Japanese pufferfish, Fugu rubripes.

The first IL-6 sequence in fish has been determined in Fugu rubripes by exploiting the synteny that is found between some regions of the human and Fugu genomes. The predicted 227 aa IL-6 homologue contains the IL-6/G-CSF/MGF motif, has a predicted secondary structure of four alpha-helixes but only contains two of the four cysteines important in disulphide bond formation. It shows low amino acid identities (20-29%) with known IL-6 sequences, although phylogenetic analysis groups the Fugu molecule with the other IL-6 molecules. The gene organisation of Fugu IL-6 and the level of synteny between the human and Fugu genomes has been well conserved during evolution with the order and orientation of the genes matching exactly to human chromosome 7. PHA stimulation of Fugu kidney cells resulted in a large increase in the Fugu IL-6 transcript, whereas LPS and Poly I:C resulted in a significant increase within spleen cells. The discovery of IL-6 in fish will now allow more detailed investigations of local inflammatory responses.

Amino Acid Sequence↗
PubMed2004

Characterisation and expression analysis of interleukin 2 (IL-2) and IL-21 homologues in the Japanese pufferfish, Fugu rubripes, following their discovery by synteny.

This investigation provides the first conclusive evidence for the existence of the interleukin 2 (IL-2) and IL-21 genes in bony fish. The IL-2 and IL-21 sequences have been determined in Fugu rubripes by exploiting the conservation of synteny that is found between regions of the human and Fugu genomes. The predicted 149-amino acid IL-2 homologue contains the IL-2 family signature, has a predicted secondary structure of three alpha helixes and has the two cysteines important in disulphide-bond formation. It shows low amino acid identities (24-34%) with other known IL-2 sequences. The predicted 155-amino acid IL-21 homologue has a predicted secondary structure of four alpha helixes and has the four cysteines important in disulphide-bond formation. It shows low amino acid identities (29-31%) with other known IL-21 sequences. The gene organisation of Fugu IL-2 and IL-21 and the level of synteny between the human and Fugu genomes has been well conserved during evolution, with the order and orientation of the genes matching exactly to human Chromosome 4. Phytohaemagglutinin stimulation of Fugu kidney cells resulted in a large increase in the Fugu IL-2 and IL-21 transcripts. In vivo stimulation of Fugu with LPS and poly I:C showed IL-21 expression to be localised within mucosal tissues. The discovery of IL-2 and IL-21 in fish will now allow more detailed investigations into T-helper cell responses.

Amino Acid Sequence↗
PubMed2004

Identification and expression analysis of an IL-18 homologue and its alternatively spliced form in rainbow trout (Oncorhynchus mykiss).

A homologue of interleukin 18 has been identified from rainbow trout, Oncorhynchus mykiss. The trout IL-18 gene spans 3.7 kb and consists of six exons and five introns, sharing the same gene organization with its human counterpart. The putative translated protein is 199 amino acids in length with no predicted signal peptide. Analysis of the multiple sequence alignment reveals a conserved ICE cut site, resulting in a mature peptide of 162 amino acids. The trout IL-18 shares 41-45% similarity with known IL-18 molecules and contains an IL-1 family signature motif. It is constitutively expressed in a wide range of tissues including brain, gill, gut, heart, kidney, liver, muscle, skin and spleen. Transcription is not modulated by lipopolysaccharide, poly(I:C) or trout recombinant IL-1beta in primary head kidney leucocyte cultures and RTS-11 cells, a macrophage cell line. However, expression is downregulated by lipopolysaccharide and rIL-1beta in RTG-2 cells, a fibroblast-like cell line. An alternatively spliced form of IL-18 mRNA has also been found and translates into a 182 amino acid protein with a 17 amino acid deletion in the precursor region of the authentic form. This alternatively spliced form is also widely expressed although much lower than the authentic form. Interestingly, its expression is upregulated by lipopolysaccharide and poly(I:C), but is not affected by rIL-1beta in RTG-2 cells. The present study suggests that alternative splicing may play an important role in regulating IL-18 activities in rainbow trout.

Alternative Splicing↗