The process of a Y-loss event in an XO/XO mammal, the Ryukyu spiny rat

Chromosoma. 2010 Oct;119(5):519-26. doi: 10.1007/s00412-010-0275-8. Epub 2010 May 5.


The Ryukyu spiny rat, Tokudaia osimensis, has an XO/XO sex chromosome constitution, lacking a Y chromosome and the mammalian sex-determining gene SRY. To investigate the Y-loss event, we traced three proto-Y-linked genes, RBMY1A1, EIF2S3Y, and KDM5D, in the genome. The original Y-linked RBMY1A1 was lost as well as SRY, and the remaining RBMY1A1 was a processed pseudogene on autosome. In contrast, EIF2S3Y and KDM5D were conserved in genomes of both sexes as a result of their translocation from the Y chromosome to the X chromosome and/or autosomes. Furthermore, these genes were expressed in gonads and brains of both sexes. Our study indicated a loss of Y-linked genes with important male functions to be necessary for the Y chromosome to disappear. These functions might have been retained through the acquisition of new genes, and therefore, the Y-loss has had no harmful effect on the maintenance of this species.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Chromosome Mapping
  • Cytogenetic Analysis
  • DNA-Binding Proteins / genetics
  • Female
  • Gene Expression
  • Genes, X-Linked
  • Genes, Y-Linked*
  • Genes, sry
  • Humans
  • In Situ Hybridization, Fluorescence
  • Male
  • Meiosis
  • Mice
  • Murinae / genetics*
  • Nuclear Proteins / genetics
  • Pseudogenes
  • Sex Chromosome Aberrations
  • Sex-Determining Region Y Protein / genetics
  • Spermatogenesis
  • Translocation, Genetic*
  • X Chromosome / genetics
  • Y Chromosome / genetics*
  • Y Chromosome / ultrastructure


  • DNA-Binding Proteins
  • Nuclear Proteins
  • Sex-Determining Region Y Protein
  • Sry protein, mouse