This mouse is heterozygous for Dnmt1 mutation. It's cryopreserved at Jackson Lab.
"Mice homozygous for this mutation die at mid-gestation. The embryos are stunted and show a delayed development. DNA from these mice shows a reduction in the level of m5C to about 1/3 that seen in cells from normal wild type siblings."
(http://jaxmice.jax.org/strain/002123.html)