title: Recent adaptive events in human brain revealed by meta-analysis of positively selected genes.
abstract: OBJECTIVE
  Analysis of positively-selected genes can help us understand how human evolved, especially the evolution of highly developed cognitive functions. However, previous works have reached conflicting conclusions regarding whether human neuronal genes are over-represented among genes under positive selection.
  
  
  RESULTS
  We divided positively-selected genes into four groups according to the identification approaches, compiling a comprehensive list from 27 previous studies. We showed that genes that are highly expressed in the central nervous system are enriched in recent positive selection events in human history identified by intra-species genomic scan, especially in brain regions related to cognitive functions. This pattern holds when different datasets, parameters and analysis pipelines were used. Functional category enrichment analysis supported these findings, showing that synapse-related functions are enriched in genes under recent positive selection. In contrast, immune-related functions, for instance, are enriched in genes under ancient positive selection revealed by inter-species coding region comparison. We further demonstrated that most of these patterns still hold even after controlling for genomic characteristics that might bias genome-wide identification of positively-selected genes including gene length, gene density, GC composition, and intensity of negative selection.
  
  
  CONCLUSIONS
  Our rigorous analysis resolved previous conflicting conclusions and revealed recent adaptation of human brain functions.
authors.affiliation: Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, People's Republic of China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Huang
authors.forename: Chen
authors.initials: C
authors.lastname: Xie
authors.forename: Adam Y
authors.initials: AY
authors.lastname: Ye
authors.forename: Chuan-Yun
authors.initials: CY
authors.lastname: Li
authors.forename: Ge
authors.initials: G
authors.lastname: Gao
authors.forename: Liping
authors.initials: L
authors.lastname: Wei
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D001921:Brain / Q000502:physiology*; D019295:Computational Biology; D030561:Databases, Nucleic Acid; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D023281:Genomics; D006801:Humans; D058977:Molecular Sequence Annotation; D009928:Organ Specificity / Q000235:genetics; D012641:Selection, Genetic