Predominant patterns of splicing evolution on human, chimpanzee and macaque evolutionary lineages.

Although splicing is widespread and evolves rapidly among species, the mechanisms driving this evolution, as well as its functional implications, are not yet fully understood. We analyzed the evolution of splicing patterns based on transcriptome data from five tissues of humans, chimpanzees, rhesus macaques and mice. In total, 1526 exons and exon sets from 1236 genes showed significant splicing differences among primates. More than 60% of these differences represent constitutive-to-alternative exon transitions while an additional 25% represent changes in exon inclusion frequency. These two dominant evolutionary patterns have contrasting conservation, regulation and functional features. The sum of these features indicates that, despite their prevalence, constitutive-to-alternative exon transitions do not substantially contribute to long-term functional transcriptome changes. Conversely, changes in exon inclusion frequency appear to be functionally relevant, especially for changes taking place in the brain on the human evolutionary lineage.