Findings on Fugu gene splicing could help scientists develop pufferfish transgenes for mammalian cells, say researchers at Massachusetts Institute of Technology. The Fugu genome contains all the alternative promoters and splice exons and introns present in mammalian genomes, but because the introns are so much smaller, genes are about an eighth the size, says MIT's Christopher Burge. This makes the Fugu genome a potentially powerful tool for functional gene analysis, he says, but scientists have until now been frustrated in their attempts to use them because mammalian cells do not correctly splice the fish genes.