Heritable epigenetic control of gene expression is essential for the early development of most organisms. One protein involved in this process is enhancer of zeste 2 (Ezh2), which is maternally inherited, contains a conserved SET domain and is involved in methylating lysine residues on histone tails. To investigate the role of Ezh2 in early mouse development, Erhardt et al. used a conditional Ezh2 allele to deplete oocytes of maternal Ezh2 (see ). Even though embryonic transcription of Ezh2 occurred as early as the four-cell stage, loss of maternal Ezh2 resulted in severely retarded foetal and neonatal growth. The authors attribute this effect to the disruption of the asymmetry in histone methylation that is normally established in the zygote by maternal Ezh2. They also report that maternal Ezh2 is required for crucial epigenetic changes in trophectoderm and epiblast cells.
