Multiple CC chemokines in channel catfish and blue catfish as revealed by analysis of expressed sequence tags

Chemokines represent a superfamily of chemotactic cytokines involved in recruitment, activation and adhesion of a variety of leukocyte types to inflammatory foci, as well as in the organization and maintenance of lymphoid organ architecture and in normal developmental processes. Nearly all chemokines have been identified in human and mouse, but only a handful of fish chemokines have been identified. Here we describe 14 distinct chemokines from channel catfish and blue catfish identified by analysis of 30,000 expressed sequence tags. Based on sequence analysis, sequence similarity, and the arrangement of the conserved cysteine residues, all 14 chemokines were identified as members of the CC subfamily. Phylogenetic analysis did not reveal clear evidence of orthology of the catfish and human or mouse chemokines. Similarity analysis indicated that nine of the 14 CC chemokines were identified for the first time in fish. The availability of this pool of catfish CC chemokines should facilitate rapid identification and phylogenetic analysis of CC chemokines from other fish and related species.