Rederivation of mouse strains to achieve pathogen-free status
The Core can assist in rederivation experiments by performing embryo transfer surgeries, or caesarian section. Rederivation must be coordinated with Vet staff. To plan and arrange for preservation experiments, contact the TG Core Supervisor, and the BRC vet staff.
Rederivation is used to establish Specific Pathogen Free (SPF) mice. We transfer preimplantation embryos into SPF pseudopregnant recipient females. This procedure is more reliable than caesarian delivery for removal of pathogens. All strains of mice can be rederived, but the efficiency of the procedure depends on the robustness and fecundity of the strain. Inbred strains require larger starting numbers of mice for a reasonable chance of success. The number of mice/breeding pairs required depends on the Investigator's needs. To maximize chances of successful rederivation, the stud males must be proven breeders that are older than 2 months of age, and less than a year old. Males should be housed individually for at least one week prior to mating. If it has been some time since they have mated or if it is their first time, a female should be placed with the male 2 weeks before mating for rederivation, and then removed one week before use for rederivation. Superovulation works best on sexually immature females in a narrow window of 3-4 weeks of age, and on sexually mature young females. Thus, for best results females should be either 3-4 weeks old or 6-8 weeks old. Rederivation includes the breeding of males with superovulated females, collection of pre-implantation stage embryos, washing/culturing of embryos, and the transfer of embryos into recipient females. The Core will provide the hormones for superovulation, perform the hormone injections and mating of the mice to be rederived, provide pseudopregnant recipient females, transfer the embryos to recipients, and house the resultant mice until weaning (3-4 weeks after mating). The recipient females will be housed in quarantine until serology tests can be performed to ensure the SPF status. Serology testing is performed upon weaning of the pups, at 3 weeks of age. The cost of the serology testing is paid for by the requesting Investigator.