Submitted to: Animal Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2005
Publication Date: 10/20/2005
Citation: Li, R.W., Silverstein, P.S., Waldbieser, G.C. 2005. Genomic characterization and expression analysis of the baculoviral iap repeat containing 2 (birc2) gene in channel catfish, ictalurus punctatus. Animal Genetics 36:537-539. Interpretive Summary: Apoptosis is a fundamental biological process that serves many functions including the prevention of uncontrolled cell proliferation and the elimination of damaged or infected cells. To date, there is little knowledge of the genetic control of apoptosis in fish. Toward that goal, we used genomic technologies to identify the gene encoding baculoviral IAP repeat containing 2 (BIRC2) in channel catfish. Catfish BIRC2 was similar in gene structure and amino acid sequence to mammalian counterparts, and expression of the catfish BIRC2 gene was reduced, as expected, when cells were induced to undergo apoptosis. The gene was also placed on the genetic map to provide a conserved gene marker for comparisons between the genomes of catfish and other vertebrates. Identification of the catfish BIRC2 gene will help researchers understand the genetic pathways controlling catfish development, cell differentiation, and host defense against infection by pathogens.
Technical Abstract: Clones containing the gene for baculoviral IAP repeat containing 2 (BIRC2) were identified by PCR screening of a gynogenetic channel catfish (Ictalurus punctatus) BAC library. Directed sequencing of ~9.5 kb of the BAC clones revealed eight exons and seven introns in the catfish BIRC2 gene. Expression of BIRC2 was detected in blood, anterior kidney and spleen, and was down-regulated 3-fold in actinomycin D-induced apoptotic leukocytes compared to normal leukocytes. A polymorphic microsatellite locus (TAA20CAA9) was identified from the BAC clone containing BIRC2, and genotype analysis revealed 16 alleles in 37 random-bred channel catfish from commercial farms. The 255bp and 264bp alleles were most frequent and made up 34% of the total number of alleles in this population. Mendelian inheritance of alleles permitted placement of the IAP1 locus on the catfish genetic linkage map. The BIRC2 locus was completely linked to marker IpCG0092 in the middle of linkage group U12 on the basis of 70 informative meioses.