The Japanese pufferfish
This fish has been used in medical research for many years. It produces a fatal neurotoxin, which has been fundamental to our understanding of how nerves function. The pufferfish toxin, TTX, irreversibly blocks sodium channels in the membranes of nerve cells, disrupting the electro-chemical forces which the cells need to function. The toxin shuts down the nervous system and these properties render the toxin fatal within minutes allow researchers to shut down particular aspects of the nervous system and understand its firing patterns more clearly.
More recently the Japanese pufferfish has been found to possess another unique property: its genome is just 400 million base-pairs long – the shortest of any vertebrate. This is 25% of the length of the zebrafish genome, and only around 10% of the length of the human genome. The organisation of pufferfish genes is different to those of humans and zebrafish, with less ‘spacer’ DNA between the genes, and almost no repetitive sequences of DNA.
Because the pufferfish genome is compact it is easier to analyse the genome and identify genes. Its genome sequence was published in 2002, and over 30,000 genes were found. As with the mouse and zebrafish, many genes found in pufferfish have conter-parts in humans, and the sequencing of the pufferfish genome helped reveal over 1000 previously unrecognized human genes.
- Aparicio, S. et al. (2002) Whole-genome shotgun assembly and analysis of the genome of Fugu rubripes, Science 297 (5585): 1301-1310