When you think of research into human conditions, most people would not consider fish to be good test subjects. They don't have arms or legs, they breathe under water and they aren't even mammals. They can't respond to surveys or tell researchers about side effects of a medication or be sorted into groups based on family history of certain diseases. What good are fish, when other animals like chimpanzees are so much closer to humans?
As it turns out, there is a species of fish that has featured very prominently in research into human health. The zebrafish, or danio rerio, has been used extensively in cellular biology research studies and scientists are learning quite about from this little fish. Researchers at the Wellcome Trust Sanger Institute and the Genome Analysis Center, both in the UK, have demonstrated that 70 per cent of protein-coding human genes are related to genes found in the zebrafish and that 84 per cent of genes known to be associated with human disease have a zebrafish counterpart. Their study highlights the importance of zebrafish as a model organism for human disease research.
The team developed a high-quality annotated zebrafish genome sequence to compare with the human reference genome. Only two other large genomes have been sequenced to this high standard: the human genome and the mouse genome. The completed zebrafish genome will be an essential resource that drives the study of gene function and disease in people.
The zebrafish genome also has some unique features, not seen in other vertebrates. They have the highest repeat content in their genome sequences so far reported in any vertebrate species: almost twice as much as seen in their closest relative, the common carp. The team also identified chromosomal regions that influence sex determination and these regions are unique to the zebrafish.
There are some differences, of course, in the zebrafish genome compared to the human genome. The zebrafish genome contains few pseudogenes - genes thought to have lost their function through evolution - compared to the human genome. The team identified 154 pseudogenes in the zebrafish genome, a fraction of the 13,000 or so pseudogenes found in the human genome.
Zebrafish research has already led to advances in cancer and heart disease research, and is furthering the understanding of muscle and organ development. Researchers are hopeful that the sequencing completed in this project will lead to additional advances in the treatment of many more human diseases.
"The vast majority of human genes have counterparts in the zebrafish, especially genes related to human disease," says Professor Jane Rogers, senior author formerly at The Genome Analysis Centre. "This high quality genome is testament to the many scientists who worked on this project and will spur biological research for years to come.
For a tiny little fish, barely two inches long and normally found in home aquariums, the benefits to medical science could be far reaching. Not bad for a little a striper.
