Submitted to: Fish and Shellfish Immunology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/1/2005
Publication Date: 1/1/2006
Citation: Li, R.W., Waldbieser, G.C. 2006. Genomic organization and expression of the natural killer cell enhancing factor (nkef) gene in channel catfish, ictalurus punctatus (rafinesque). Fish and Shellfish Immunology 20:72-82. Interpretive Summary: Disease losses significantly reduce the efficiency of channel catfish production, and the industry would benefit from catfish lines that are more disease resistant. In order to better understand the molecular basis of response to bacterial pathogens, a gene was identified in catfish that has been shown in other species to enhance the action of immune cells. The Natural Killer Cell Enhancing Factor (NKEF) gene was cloned, the gene demonstrated expression in multiple tissues, and gene expression was slightly increased after exposure of fish to components of the bacterial cell wall. The gene was placed on the catfish genetic linkage map for future comparative studies with other species. This research provided new molecular tools useful for examining cellular responses to pathogen invasion, and eventual identification and selection of catfish with higher resistance to disease.
Technical Abstract: The gene encoding Natural Killer Cell Enhancing Factor (NKEF) was identified in clones from a gynogenetic channel catfish BAC library. NKEF gene sequence (5.2 kb) was obtained by direct sequencing of BAC clones. The catfish NKEF gene contains one non-coding exon, five coding exons and five introns. A putative TATA box and other transcription factor binding sites were identified in the promoter region. The NKEF amino acid sequence is highly conserved between fish and mammals. Gene expression, measure by real-time quantitative PCR, was detected in all major tissues with the highest level of expression in stomach and heart and lowest levels in gonad and pituitary gland. Catfish NKEF mRNA levels were slightly upregulated 8 and 24 hours after injection of lipopolysaccharide. A TAA-repeat microsatellite was identified in a BAC clone containing the NKEF gene, and this locus contained at least 12 alleles in a random-bred catfish population. Multipoint linkage analysis in two reference families placed the NKEF gene on linkage group U18, 5.1 cM from locus IpCG0177 (r = 0.05; LOD = 45.8), 6.0 cM from a novel immune type receptor, syntenic (40cM) with T-cell receptor ', and not linked with MHC loci.