CC chemokines in zebrafish: evidence for extensive intrachromosomal gene duplications

Chemokines are a family of structurally related chemotactic cytokines that regulate the migration of leukocytes. CC chemokines represent the largest subfamily of chemokines, with 28 genes in mammals. In recent studies in channel catfish, Ictalurus punctatus, we identified 26 distinct CC chemokine transcripts and obtained the genomic sequences and structures of 23 CC chemokine genes. However, without the availability of similar sets of CC chemokines in closely related species or a sequenced genome in catfish, it was difficult to make inferences as to the origins and modes of duplication of these molecules or to analyze conserved synteny between teleost and mammalian CC chemokines. Here, we have identified as many as 46 loci in the zebrafish genome that encode putative CC chemokines. The zebrafish CC chemokines are highly clustered on several chromosomes and show evidence of extensive, species-specific intrachromosomal duplications.