MicroRNA-9: functional evolution of a conserved small regulatory RNA

RNA Biol. Jul-Aug 2011;8(4):557-64. doi: 10.4161/rna.8.4.16019. Epub 2011 Jul 1.


The functional significance of microRNA-9 (miR-9) during evolution is evidenced by its conservation at the nucleotide level from flies to humans but not its diverse expression patterns. Recent studies in several model systems reveal that miR-9 can regulate neurogenesis through its actions in neural or non-neural cell lineages. In vertebrates, miR-9 exerts diverse cell-autonomous effects on the proliferation, migration, and differentiation of neural progenitor cells by modulating different mRNA targets. In some developmental contexts, miR-9 suppresses apoptosis and is misregulated in several types of cancer cells, influencing proliferation or metastasis formation. Moreover, downregulation of miR-9 in postmitotic neurons is also implicated in some neurodegenerative diseases. Thus, miR-9 is emerging as an important regulator in development and disease through its ability to modulate different targets in a manner dependent on the developmental stage and the cellular context.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Animals
  • Apoptosis / genetics
  • Biological Evolution*
  • Cell Differentiation / genetics
  • Cell Movement / genetics
  • Cell Proliferation
  • Humans
  • MicroRNAs* / biosynthesis
  • MicroRNAs* / genetics
  • MicroRNAs* / metabolism
  • Neoplasm Metastasis / genetics
  • Neoplasms / genetics*
  • Neurogenesis / genetics*


  • MIRN92 microRNA, human
  • MicroRNAs