Mouse Embryo Cryopreservation

Due to the inherent value of genetically altered mouse strains, we offer cryopreservation of individual mouse strains housed at Yale University. Strains will be cryopreserved in the order in which requests are submitted. Please read the following information carefully to understand the benefits and limitations of cryopreservation.

Provision of Animals

Investigators should contact the cryopreservation service once they have ascertained that they have sufficient numbers (see below) of fertile male and, if needed, female mice. A minimum of five males aged 2 to 5 months should be provided by the investigator. Depending on strain background requirements, females aged 3-4 weeks may be supplied by the investigator or purchased from an approved SPF vendor. All mice remain on the census of the investigator during the cryopreservation process. Females will be superovulated by the AGS and mated with males, and embryos will be harvested on e2.5 and cryopreserved. This procedure will be repeated until a sufficient number of embryos are cryopreserved.


Gestational day 2.5 embryos are isolated and cryopreserved in straws and stored in liquid N2. The first and last straw are subsequently thawed and transferred to foster females to demonstrate viability of the line with the assumption that all embryos frozen between the first and last straw will behave similarly. If homozygous embryos are preserved, we recommend the storage of at least 150 embryos, in addition to those frozen and thawed to ascertain viability. If heterozygous embryos are preserved, we recommend the storage of approximately twice that number. If viable progeny are not observed, a second embryo transfer will be performed.

Other Considerations

The success and cost of cryopreservation is dependent upon the fertility of the animals used and the response of the females to superovulatory hormones. The most efficient strategy is to use 3-4-week old B6SJLF1 females supplied by a commercial vendor. However, it is appreciated that in many instances investigators must work within strain background constraints that preclude this option. In those instances, we will cryopreserve embryos on the appropriate genetic background, if it is possible to do so, realizing that more attempts and more mice (and hence higher costs) will likely be required.

There will be a yearly liquid N2 fee to maintain the embryos in two separate liquid N2 tanks in our facility.