Analysis of Medaka sox9 Orthologue Reveals a Conserved Role in Germ Cell Maintenance

PLoS One. 2012;7(1):e29982. doi: 10.1371/journal.pone.0029982. Epub 2012 Jan 12.


The sex determining gene is divergent among different animal species. However, sox9 is up-regulated in the male gonads in a number of species in which it is the essential regulator of testis determination. It is therefore often discussed that the sex determining gene-sox9 axis functions in several vertebrates. In our current study, we show that sox9b in the medaka (Oryzias latipes) is one of the orthologues of mammalian Sox9 at syntenic and expression levels. Medaka sox9b affects the organization of extracellular matrices, which represents a conserved role of sox9, but does not directly regulate testis determination. We made this determination via gene expression and phenotype analyses of medaka with different copy numbers of sox9b. Sox9b is involved in promoting cellular associations and is indispensible for the proper proliferation and survival of germ cells in both female and male medaka gonads. Medaka mutants that lack sox9b function exhibit a seemingly paradoxical phenotype of sex reversal to male. This is explained by a reduction in the germ cell number associated with aberrant extracellular matrices. Together with its identified roles in other vertebrate gonads, a testis-determining role for Sox9 in mammals is likely to have been neofunctionalized and appended to its conserved role in germ cell maintenance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Animals
  • Apoptosis / genetics
  • Base Sequence
  • Cell Count
  • Cell Proliferation
  • Cell Survival
  • Conserved Sequence*
  • Extracellular Matrix / metabolism
  • Female
  • Gene Expression Regulation
  • Germ Cells / cytology*
  • Germ Cells / metabolism*
  • Heterozygote
  • Male
  • Molecular Sequence Data
  • Mutation / genetics
  • Oryzias / genetics
  • Oryzias / metabolism*
  • Phenotype
  • SOX9 Transcription Factor / chemistry*
  • SOX9 Transcription Factor / genetics
  • SOX9 Transcription Factor / metabolism*
  • Sequence Homology, Amino Acid
  • Sex Determination Processes / genetics
  • Sex Differentiation / genetics
  • Synteny / genetics
  • Testis / cytology
  • Testis / metabolism


  • SOX9 Transcription Factor