The effect of interspecific oocytes on demethylation of sperm DNA

Proc Natl Acad Sci U S A. 2004 May 18;101(20):7636-40. doi: 10.1073/pnas.0400730101. Epub 2004 May 10.


In contrast to mice, in sheep no genome-wide demethylation of the paternal genome occurs within the first postfertilization cell cycle. This difference could be due either to an absence of a sheep demethylase activity that is present in mouse ooplasm or to an increased protection of methylated cytosine residues in sheep sperm. Here, we use interspecies intracytoplasmic sperm injection to demonstrate that sheep sperm DNA can be demethylated in mouse oocytes. Surprisingly, mouse sperm can also be demethylated to a limited extent in sheep oocytes. Our results suggest that the murine demethylation process is facilitated either by a sperm-derived factor or by male pronuclear chromatin composition.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • DNA / metabolism*
  • DNA Methylation*
  • Female
  • Gene Expression Regulation, Developmental / physiology
  • Male
  • Mice
  • Microscopy, Confocal
  • Oocytes / metabolism*
  • Sheep / genetics*
  • Sperm Injections, Intracytoplasmic
  • Spermatozoa / metabolism*


  • DNA