Evolutionary and ontogenetic changes in RNA editing in human, chimpanzee, and macaque brains.

Adenosine-to-inosine (A-to-I) substitutions are the most common type of RNA editing in mammals. A-to-I RNA editing is particularly widespread in the brain and is known to play important roles in neuronal functions. In this study we investigated RNA-editing changes during human brain development and maturation, as well as evolutionary conservation of RNA-editing patterns across primates. We used high-throughput transcriptome sequencing (RNA-seq) to quantify the RNA-editing levels and assess ontogenetic dynamics of RNA editing at more than 8000 previously annotated exonic A-to-I RNA-editing sites in two brain regions--prefrontal cortex and cerebellum--of humans, chimpanzees, and rhesus macaques. We observed substantial conservation of RNA-editing levels between the brain regions, as well as among the three primate species. Evolutionary changes in RNA editing were nonetheless evident, with 40% of the annotated editing sites studied showing divergent editing levels among the three species and 16.5% of sites displaying statistically significant human-specific editing patterns. Across lifespan, we observed an increase of the RNA-editing level with advanced age in both brain regions of all three primate species.