title: Origin of primate orphan genes: a comparative genomics approach.
abstract: Genomes contain a large number of genes that do not have recognizable homologues in other species and that are likely to be involved in important species-specific adaptive processes. The origin of many such "orphan" genes remains unknown. Here we present the first systematic study of the characteristics and mechanisms of formation of primate-specific orphan genes. We determine that codon usage values for most orphan genes fall within the bulk of the codon usage distribution of bona fide human proteins, supporting their current protein-coding annotation. We also show that primate orphan genes display distinctive features in relation to genes of wider phylogenetic distribution: higher tissue specificity, more rapid evolution, and shorter peptide size. We estimate that around 24% are highly divergent members of mammalian protein families. Interestingly, around 53% of the orphan genes contain sequences derived from transposable elements (TEs) and are mostly located in primate-specific genomic regions. This indicates frequent recruitment of TEs as part of novel genes. Finally, we also obtain evidence that a small fraction of primate orphan genes, around 5.5%, might have originated de novo from mammalian noncoding genomic regions.
authors.affiliation: Evolutionary Genomics Group, Biomedical Informatics Research Programme, Fundació Institut Municipal d'Investigació Mèdica, Barcelona, Spain.
authors.forename: Macarena
authors.initials: M
authors.lastname: Toll-Riera
authors.forename: Nina
authors.initials: N
authors.lastname: Bosch
authors.forename: Nicolás
authors.initials: N
authors.lastname: Bellora
authors.forename: Robert
authors.initials: R
authors.lastname: Castelo
authors.forename: Lluis
authors.initials: L
authors.lastname: Armengol
authors.forename: Xavier
authors.initials: X
authors.lastname: Estivill
authors.forename: M Mar
authors.initials: MM
authors.lastname: Albà
mesh_terms: D000818:Animals; D003062:Codon; D004251:DNA Transposable Elements; D019143:Evolution, Molecular; D016678:Genome; D023281:Genomics / Q000379:methods*; D006801:Humans; D010455:Peptides; D011323:Primates / Q000235:genetics*; D014018:Tissue Distribution
chemical_list: D003062:Codon; D004251:DNA Transposable Elements; D010455:Peptides