Table 1.

Phenotypes of initial Dnmt knockout mouse models.

Genotype	Phenotype	Reference
Dnmt1 null	Homozygous knockout Dnmt1 were stunted, delayed in development, and did not survive past midgestation	Li et al., 1992
Dnmt3a null	Knockout mice developed to term and appeared to be normal at birth but most of homozygous mutant mice became runted and died at about 4 weeks of age	Okano et al., 1999
Dnmt3b null	No viable Dnmt3b knockout mice were recovered at birth	Okano et al., 1999
Dnmt2 null	Mice homozygous for this Trdmt1 (formerly Dnmt2) knock-out have abnormal RNA methylation while genomic DNA methylation patterns are not detectably altered	Goll et al., 2006
Dnmt3l null	Disruption of Dnmt3l caused azoospermia in homozygous males and heterozygous progeny of homozygous female died before midgestation	Bourc’his et al., 2001