The sophisticated mouse: protecting a precious reagent

Definable, genetically and environmentally, the humble mouse has become a reagent with which to probe the human condition. The information thus gained is leading to a greater understanding of inter-individual variation in drug responses and disease processes and is forming the basis for personalized medicine. Inbred mice are the tool of choice as each strain is essentially clonal in nature creating a defined, uniform setting where the effects of genetic background and modifications can be evaluated coherently. However, the creation and characterization of novel mouse strains remain expensive and time consuming. Further, the continual maintenance of these valuable animals as live colonies is financially draining and carries continual potential risks, including disastrous loss due to fire, flood, disease, etc. There are also other more insidious disasters including genetic contamination and genetic drift, either of which can go undiscovered until their effects ruin experiments. With this in mind, we strongly recommend that all mouse strains be cryopreserved as a matter of standard mouse management. Cryopreservation is a powerful colony management tool, assuring strains are available upon demand, for example, for regulatory requirements, re-initiation of projects, collaborations, re-evaluation of data etc. However, it is essential that any cryopreservation approach be cost-effective for both strain closure and strain recovery. In this chapter, we describe the variables which can afflict an inbred mouse's genetic background (and hence phenotype), options to consider for strain archiving, and describe how to economically store and recover strains by sperm cryopreservation.