title: Novel microRNA families expanded in the human genome.
abstract: BACKGROUND
  Most studies on the origin and evolution of microRNA in the human genome have been focused on its relationship with repetitive elements and segmental duplications. However, duplication events at a smaller scale (<1 kb) could also contribute to microRNA expansion, as demonstrated in this study.
  
  
  RESULTS
  Using comparative genome analysis and bioinformatics methods, we found nine novel expanded microRNA families enriched in short duplicated sequences in the human genome. Furthermore, novel genomic regions were found to contain microRNA paralogs for microRNA families previously analyzed to be related to segmental duplications. We found that for microRNA families expanded in the human genome, 14 families are specific to the primate lineage, and nine are non-specific, respectively. Two microRNA families (hsa-mir-1233 and hsa-mir-622) appear to be further expanded in the human genome, and were confirmed by fluorescence in situ hybridization. These novel microRNA families expanded in the human genome were mostly embedded in or close to proteins with conserved functions. Furthermore, besides the Alu element, L1 elements could also contribute to the origination of microRNA paralog families.
  
  
  CONCLUSIONS
  Together, we found that small duplication events could also contribute to microRNA expansion, which could provide us novel insights on the evolution of human genome structure and function.
authors: Department of Animal Science and Center for Integrated Animal Genomics, Iowa State University, 2255 Kildee Hall, Ames, IA 50011, USA. zhqdu@iastate.edu
authors: Zhi-Qiang
authors: ZQ
authors: Du
authors: Cai-Xia
authors: CX
authors: Yang
authors: Max F
authors: MF
authors: Rothschild
authors: Jason W
authors: JW
authors: Ross
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D015894:Genome, Human; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D020071:Interspersed Repetitive Sequences / Q000235:genetics*; D035683:MicroRNAs / Q000235:genetics*; D010802:Phylogeny; D011323:Primates; D056916:Segmental Duplications, Genomic
chemical_list: D035683:MicroRNAs
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