Although half of the human genome is derived from retrotransposons, mobilization of these elements is normally suppressed in somatic cells. By applying their newly developed, high-throughput method for detecting retrotransposon insertion sites (called retrotransposon capture sequencing (RC-seq)), Baillie and colleagues now show that L1, Alu and SVA elements are active in the germline and also in the brain. Somatic mobilization of these elements in the brain occurs preferentially in active brain genes, suggesting that insertion mosaicism contributes to normal and abnormal brain functions. Zhang and colleagues examined a different type of genetic landscape: the evolution of human-specific genes that are expressed in the brain. They compared recently evolved genes in humans and mice (those that are specific to the primate or rodent lineages, respectively) and found that young genes in humans are more likely to be expressed during early brain development. Some young genes in humans are also more likely than old genes to be upregulated in newly evolved brain regions, such as the neocortex. The suggestion is that positive selection in newly evolving brain regions has driven accelerated gene origination in the human brain.
ORIGINAL RESEARCH PAPERS
Baillie, J. K. et al. Somatic retrotransposition alters the genetic landscape of the human brain. Nature 30 Oct 2011 (doi:10.1038/nature10531)
Zhang, Y. E. et al. Accelerated recruitment of new brain development genes into the human genome. PLoS Biol. 9, e1001179 (2011)
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Casci, T. Altering the genetic landscape of the brain. Nat Rev Genet 12, 805 (2011). https://doi.org/10.1038/nrg3122