Biomedical subjects

Eva Bengten

Publications and source records attributed to Eva Bengten.

3 recordsLinked to original sources

PubMed2006

Identification and expression analysis of interferon gamma genes in channel catfish.

Multiple species of type I interferon (IFN) were recently identified in catfish (CF) (Ictalurus punctatus). Herein we extend these studies and report the existence of two distinct type II IFN genes in channel CF. As with zebrafish and the green spotted pufferfish, the two CF IFN-gamma genes are dissimilar in sequence but closely linked on the same chromosome. One of the genes (IFN-gamma2) encodes two distinct messages that likely arose via alternative splicing at two closely spaced splice donor sites within the first intron. Sequence analysis indicates that CF IFN-gamma genes contain the hallmarks of authentic IFN-gamma including: (1) a conserved nuclear localization site at the C terminus (CF IFN-gamma2 only), (2) an IFN-gamma signature sequence, (3) six putative helical regions within the mature protein, (4) one or more potential glycosylation sites, and (5) multiple mRNA instability motifs within the 3' untranslated region. Moreover, well-characterized CF T and NK cell clones were shown to synthesize IFN-gamma transcripts. This is the first unequivocal demonstration in any lower vertebrate species that NK and T cells synthesize IFN-gamma and is consistent with results in mammalian systems where T cells and NK cells are the major sources of type II IFN production. Collectively, these studies indicate that Siluriformes possess two evolutionarily conserved IFN-gamma genes and demonstrate that CF possess three key elements of the innate immune response: NK cells and types I and II IFN.

Amino Acid Sequence↗

PubMed2006

Identification and expression analysis of cDNAs encoding channel catfish type I interferons.

Previously a cDNA encoding a putative interferon gene, designated CF IFN-1, was identified from a catfish EST library. However, its constitutive expression, absence of a signal peptide, and apparently low level of biological activity suggested that this cDNA likely encoded an expressed pseudogene. Since Southern blot analysis suggested the presence of two to three IFN genes, additional cDNAs were generated from catfish fibroblast and lymphoid cell lines using primers designed to conserved regions of zebrafish and catfish interferon. Using this approach, three novel CF IFN genes, two of which likely encode functional interferon molecules, were identified. At the amino acid level, similarity among CF IFNs ranged from 71% to 82%, whereas similarity to other fish IFNs ranged from 15% to 35%. Although CF IFN-3, like CF IFN-1, lacks a signal peptide, CF IFN-2 and -4 appear to encode full-length, signal sequence-bearing genes. Consistent with their putative identification as functional genes, CF IFN-2 and -4 were not expressed in unstimulated cell lines, and CF IFN-2 was rapidly upregulated in CCO cells in response to virus infection or treatment with dsRNA. Moreover, as with salmon, fugu, and zebrafish interferon genes, CF IFN-1 contained four introns whose locations were conserved not only with respect to other fish IFNs, but also with respect to mammalian IFN-lambda. While it is likely that CF IFNs represent Type I IFNs, several characteristics preclude assigning these cytokines to any particular subfamily.

Amino Acid Sequence↗

PubMed2004

Identification of a cDNA encoding channel catfish interferon.

Despite considerable advances in our understanding of teleost immunity, relatively few cytokine genes, including those for interferon (IFN), have been identified at the molecular level. In contrast, numerous studies have shown that following virus infection or exposure to double-stranded RNA, fish or fish cells produce a soluble factor that is functionally similar to mammalian IFN. A putative catfish (CF) IFN cDNA was identified by BLASTX screening of a catfish EST library generated from a mixed lymphocyte culture enriched for NK-like cells. Consistent with its designation as a putative cytokine cDNA, the 3' non-translated region contained multiple copies of an RNA instability motif. Analysis of the deduced amino acid sequence of CF IFN showed low levels of identity/similarity to a panel of mammalian and avian IFN proteins, and markedly higher similarity to a recently identified zebrafish IFN. To determine if the identified cDNA encoded CF IFN, expression was monitored following infection of channel catfish ovary (CCO) cells with UV-inactivated catfish reovirus or exposure to double-stranded RNA, treatments which induce IFN or IFN-like activity in catfish and other species. In both cases, upregulation of putative CF IFN mRNA was detected. Moreover, upregulation of CF IFN mRNA was accompanied by the appearance of an antiviral factor in the culture medium. To confirm these results, recombinant CF IFN was synthesized in COS-7 cells and shown to have antiviral activity in CCO cells. Collectively, these results argue strongly that the identified catfish cDNA is an IFN homolog.

Amino Acid Sequence↗