Deadly Japanese fish gets inside man's genes

Unlikely similaritiies between people and the Japanese puffer fish have uncovered almost 1,000 previously unknown human genes.

Unlikely similaritiies between people and the Japanese puffer fish have uncovered almost 1,000 previously unknown human genes.

An international consortium of scientists said yesterday that it had completed a draft blueprint of the genetic make-up of the puffer fish, Fugu rubripes. The sequence contains roughly the same number of genes as the much larger human genome, but they are much more densely packed.

By comparing human and puffer fish genomes, the scientists were able to predict the existence of almost 1,000 unidentified human genes.

Most of these genes, yet to be located in the human genome, have functions that are unknown, the researchers reported in the journal Science.

Dr Samuel Aparicio, of the Wellcome Trust Centre for Molecular Mechanisms in Disease at Cambridge University, said: "For the first time we are seeing the overall differences as well as the similarities in the protein parts that make up fish and man.

"When we matched the predicted Fugu proteins directly against the human genome sequence, for 961 cases we found that there was a match in humans that didn't overlap an already predicted or known human gene.

"This flags up for human geneticists the position of potentially novel human genes. In addition, direct comparisons of the fish DNA with the human DNA show that more human genes will be found by comparing fish with man.

"The puffer fish sequence is helping to find previously undiscovered features of the human genome – a process compared with the decipherment of the Rosetta stone."

The puffer fish lacks much of the non-coding "junk" DNA that litters 97 per cent of the human genome. As a result genes that may otherwise have been obscured can be spotted.

Three-quarters of human genes appear to have identifiable counterparts in the puffer fish, highlighting the physiology common to all vertebrates.

Daniel Rokhsar, the associate director for computational genomics at the US Joint Genome Institute, said: "These similarities are recognisable in the two genome sequences despite the 400 million years since the two species diverged from their common ancestor."

The puffer fish, which blows itself up when threatened, has a unique place in Japanese culinary tradition, where it is a prized but potentially deadly delicacy. Diners pay hundreds of pounds to experience its unusual bittersweet taste, knowing it could kill them.

The fish contains a lethal poison, tetrodotoxin, which is concentrated in certain organs and can kill within four hours of being swallowed.

Japanese chefs have to take extreme care to clean the fish and separate the tissues carrying the highest concentrations of poison.