Identification of novel exons from rat-mouse comparisons.

Exon shuffling, a major mechanism of gene evolution, scrambles existing sequences to create new genes. However, is it possible for an exon to be created from scratch? Here we conduct a survey of rat and mouse genomes and identify 2302 putative rodent-specific exons absent from the human genome. Analysis of rodent transcripts supporting these exons indicates that over half appear to be alternatively spliced in genes orthologous between rodents and human. This study demonstrates the importance of sequencing genomes from multiple species to accurately document the evolution of gene structure.