Showing papers by "Zhanjiang Liu published in 2005"

Catfish hepcidin gene is expressed in a wide range of tissues and exhibits tissue-specific upregulation after bacterial infection

Abstract: Antimicrobial peptides (AMPs) are important components of the host innate immune response against microbial invasion. The cysteine-rich AMPs such as defensin and hepcidin have been extensively studied from various organisms, but their role in disease defense in catfish is unknown. As a first step, we sequenced a hepcidin cDNA from both channel catfish and blue catfish, and characterized the channel catfish hepcidin gene. The channel catfish hepcidin gene consists of two introns and three exons that encode a peptide of 96 amino acids. The amino acid sequences and gene organization were conserved between catfish and other organisms. In contrast to its almost exclusive expression in the liver in humans, the channel catfish hepcidin gene was expressed in a wide range of tissues except brain. Its expression was detected early during embryonic and larval development, and induced after bacterial infection with Edwardsiella ictaluri, the causative agent of enteric septicemia of catfish (ESC) in a tissue-specific manner. The upregulation was observed in the spleen and head kidney, but not in the liver. The expression of hepcidin was upregulated 1--3 days after challenge, but returned to normal levels at 7 days after challenge. The expression profile of the catfish hepcidin gene during the course of bacterial infection mirrors those of inflammatory proteins such as chemokines, suggesting an important role for hepcidin during inflammatory responses.

Analysis of a catfish gene resembling interleukin-8: cDNA cloning, gene structure, and expression after infection with Edwardsiella ictaluri.

Abstract: Chemokines are important mediators for innate immunity involved in recruitment, activation and adhesion of a variety of leukocyte types to inflammatory foci. While almost all chemokines have been identified from mammals, only a handful of fish chemokines have been identified. Here we report molecular cloning, sequence analysis, and expression of a channel catfish gene resembling interleukin-8 (IL-8). The gene has two alternatively spliced transcripts encoding 114 and 111 amino acids, respectively. The gene has four exons and three introns, typical of the CXC chemokine gene organization. In spite of the structural conservation through evolution, the piscine IL-8 genes showed a much greater sequence divergence than their counterparts among mammals. RT-PCR indicated that both spliced forms were expressed. Expression of the IL-8 like gene was up-regulated 3-5-fold in channel catfish and blue catfish after infection with pathogenic bacteria Edwardsiella ictaluri.

Characterization and expression analysis of bactericidal permeability-increasing protein (BPI) antimicrobial peptide gene from channel catfish Ictalurus punctatus.

Abstract: Antimicrobial peptides are important components of host defenses against microbial invasions. Bactericidal permeability-increasing protein (BPI) is an antimicrobial peptide belonging to the lipid transfer/LPS-binding protein family. It serves important roles in defending against Gram-negative bacteria in the innate immune system. Here we report cloning of complete BPI cDNA from channel catfish (Ictalurus punctatus) by 5' RACE after obtaining the partial BPI cDNA sequence from EST analysis. The channel catfish BPI cDNA is 1640 bp in length with a 1428-bp open reading frame that encodes a protein of 475 amino acids. Catfish BPI gene shows high similarity with the BPI/LBP gene isolated from other teleost fish. As part of ongoing efforts in comparative genome analysis, we have assigned the catfish BPI gene to bacterial artificial chromosome (BAC) clones. Southern blot analysis on multiple BPI BAC clones indicated the presence of a single copy of the BPI gene in the catfish genome. Reverse transcription-polymerase chain reaction (RT-PCR) analysis on healthy tissues showed that BPI was expressed in a wide range of tissues including head kidney, gill, skin, trunk kidney, brain, intestine, liver, muscle, ovary, spleen and stomach. The BPI gene was not developmentally expressed until 48 h after fertilization. Quantitative real time PCR (QRT-PCR) analysis indicated that the BPI gene expression was induced after challenge with Edwardsiella ictaluri, the causative agent of enteric septicemia of catfish (ESC). BPI upregulation peaked 3 days after challenge, mirroring the expression pattern of inflammatory chemokines in catfish, suggesting that it plays a role in the innate defense response.

In silico identification and expression analysis of 12 novel CC chemokines in catfish.

Abstract: Chemokines, a superfamily of chemotactic cytokines involved in recruitment, activation, and adhesion of a variety of leukocyte types to inflammatory foci, are a crucial component of the immune system of Sarcopterygiian vertebrates. Although all mammalian chemokines are believed to have been found, the status of these molecules in Actinopterygii was unknown until recently. The identification of chemokines in fish species has been complicated by low sequence conservation and confusion over expected numbers. Earlier discoveries of single fish chemokines coupled with rapidly expanding genetic resources in these species have recently provided a foundation for large-scale in silico discoveries of these important immune regulators. We report here the identification and expression analysis of 12 new CC chemokine sequences from catfish. When added to our previous report of 14 catfish CC chemokines, the number of CC chemokines in catfish now stands at 26, two more than known from humans. Establishing orthologous relationships among the majority of catfish CC chemokines, a newly available set of chicken CC chemokines, and their mammalian counterparts remain difficult, suggesting high levels of duplication and divergence within individual species.