Mouse and Rat Embryo Freezing and Recovery by Vitrification v1

We provide a detailed vitrification protocol for freezing and thawing embryos that can contribute to efficient mouse line management. Cryopreservation of mouse lines is essential for the efficient management of mouse lines. When mouse lines are placed in a cryo-archive it is no longer necessary to maintain breeding pairs or mice in the vivarium, thus contributing to a reduction in animal use. When a mouse line is shared with another laboratory cryogenic vials of embryos can be shipped to a receiving institution where they can be recovered as live mice. Shipping embryos in place of live mice circumvents the need to establish mice in quarantine before they are mated to produce cohorts of mice for research. A large number of mice can be produced for a cohort of similarly aged mice for a research project by transferring a large number of embryos on the same day. This approach can accelerate research and prevent the need to set up breeding cages. Placing cryopreserved embryos in several locations can protect mouse lines from environmental disasters that can affect vivariums. Cryopreserved embryos can protect against viral or bacterial pathogen contamination; against accidental genetic contamination, against phenotypic drift in due to backcrossing complex genetic makeups into defined genetic backgrounds. For a description of the role of cryopreserved embryos in the management of mouse colonies see Chapter 8 ofThe Jackson Laboratory Handbook on Genetically Standardized Mice.In summary, cryo-archives provide biosecurity for valuable genetically engineered mouse lines and facilitate the sharing of irreplaceable research resources.