Mapping of Zebrafish Expressed Sequences and the Evolution of the Vertebrate Genome

John Postlethwait
Institute of Neuroscience
University of Oregon
Eugene OR 97403 USA
telephone: 541-346-4538
fax: 541-346-4538 or 541-346-4548
email: jpostle@oregon.uoregon.edu
prestype: Platform
presenter: John H. Postlethwait

John H. Postlethwait
Institute of Neuroscience, University of Oregon, Eugene, OR 97403

Comparative mapping of zebrafish and mammalian genomes reveals large regions of conserved synteny, sometimes about as long as individual mammalian chromosomes. For example, for example results suggest that most of the loci on human chromosome 17 have remained syntenic for the last 450 million years, since the divergence of ray-fin and lobe-fin fish. Within conserved regions, however, frequent intrachromosomal rearrangements have altered gene order. Duplicated chromosome segments suggest that a genome duplication occurred in the lineage leading to zebrafish. Comparison with other teleosts suggest this event may have occurred deep in the ancestry of teleost fish. Genetic maps show that about 30% of zebrafish genes may be retained from this event. Analysis of expression patterns of duplicated genes derived from this event suggest that duplicated gene pairs have frequently partitioned ancestral functions between the two copies. Despite this genome duplication event, teleost fish and mammals have about the same number of chromosomes. Mapping data were analyzed to test the hypotheses that current chromosome numbers are due to either an excess of chromosome fissions in the human lineage or an excess of chromosome fusions in the fish lineage, and the latter seems more likely. These investigations will help improve connectivities between mammalian and fish genomes, and thus speed our understanding of gene function in both groups of animals.



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