[Cryopreservation of transgenic mouse embryos by ultrarapid freezing]

Two transgenic mice lines were produced by introducing the rat GH antisense transgene and the chicken beta-actin promoter/firefly luciferase hybrid gene in our laboratory. We cryopreserved the transgenic embryos, obtained by fertilization in vitro with the sperm of hemizygous males for the transgene, by the ultrarapid freezing. The survival rates of cryopreserved 2-cell embryos were high (> 70%) at thawing in both lines and 53% and 16% of cryopreserved 2-cell embryos, respectively, developed to live young after transferring to oviducts of recipients. Each transgene was detected at about 40% of the live young from two transgenic lines. These results indicated that the cryopreservation of embryos by ultrarapid freezing was valuable for sustaining transgenic mouse lines without genetic contaminations.