Patterns of DNA methylation are laid out during early embryogenesis via the interplay of at least three active DNA methyltransferases, DNMT1, DNMT3A, and DNMT3B, and targeted deletions of these genes in the mouse have demonstrated that the enzymes are essential for normal development.

DNMT3A and DNMT3B are de novo methyltransferases important for establishing methylation patterns during embryogenesis, and they associate with the replication fork in late S-phase during the replication of constitutive heterochromatin.

Pathology

 germline mutations of DNMT3B in ICF syndrome (immunodeficiency syndrome, chromosome instability, facial anomalies syndrome) (MIM.242860)

References

Xu, G.-L.; Bestor, T. H.; Bourc'his, D.; Hsieh, C.-L.; Tommerup, N.; Bugge, M.; Hulten, M.; Qu, X.; Russo, J. J.; Viegas-Pequignot, E. : Chromosome instability and immunodeficiency syndrome caused by mutations in a DNA methyltransferase gene. Nature 402: 187-191, 1999. PubMed ID : 10647011