COMPARATIVE GENOMICS OF ZEBRAFISH

Institute of Neuroscience, 1254 University of Oregon, Eugene, OR 97403, U.S.A.

Do teleost fishes have specialized genome characteristics relevant to aquaculture? To investigate genomic issues in teleost fishes we have constructed genetic maps for the zebrafish Danio rerio and compared the maps to those of humans and other vertebrates. The maps show extensive regions of conserved syntenies between zebrafish and human genomes. For example, LG03 of zebrafish has 20 loci with orthologues widely distributed on human chromosome 17 (Hsa17). Furthermore, the zebrafish frequently has two copies of many human chromosomes. For example, LG12 of zebrafish has 10 loci whose orthologues are on Hsa17. Four of those loci have duplicate copies on LG03 and LG12 (hoxba/hoxbb, rara2a/rara2b, dlx7/dlx8, and sox9a/sox9b), both of which are orthologous to an Hsa17 gene (HOXB, RARA, DLX7,and SOX9). Because other chromosomes have similar duplicated regions, we conclude that there was a genome duplication in the lineage leading to zebrafish after it split with the lineage leading to human. We suggest that there may have been a genome duplication after the divergence of ray finned fishes and lobe finned fishes, but before the teleost radiation. Thus, most teleosts may share an ancient common genome duplication event. This extra gene specialization in teleosts may provide specialized functions that might be relevant to the aquaculture of teleost fishes.