Embryo Cryopreservation for Transgenic Mouse Lines

Embryo cryopreservation can greatly assist in the management of transgenic mice by providing a low cost means of storing mouse lines or strains while they are not needed (3 ,12 ,13 ,19 ,27 ,31 ). There are several cryopreservation protocols which are very effective for mouse embryos. The cryopreservation protocol described in this paper is a vitrification method which requires no specialised equipment other than a liquid nitrogen tank for long term storage and the plastic straws in which the embryos are cryopreserved (8 ,9 ). It is one of the simplest and most effective protocols for mouse morulae. It only takes 1 min before the embryos can be placed in liquid nitrogen for long term storage. Cryopreserved mouse lines can be reestablished as required by warming the embryos and transferring them to recipient mice (see Note 1 ). Transfers can be carried out as little as 10 min after removing the embryos from liquid nitrogen. While the embryos are in storage, they are cheap to maintain (cost of liquid nitrogen), do not display genetic drift, and cannot be lost due to infection or disease (12 ,31 ).