Cryopreservation

Information about embryo and sperm cryopreservation services

Reasons to consider cryopreservation

Maintenance of rodent colonies can be expensive and time consuming. Cryopreservation using sperm or embryos offers an alternative to maintenance breeding to preserve a rodent line that is not currently in use.
Back-up to preserve the line in the event that the colony becomes pathogen compromised, has a fertility issue or background/genotype is compromised.
Transport of cryopreserved material can be the most straight-forward way of sharing lines with collaborators.

CTC offers both sperm and embryo cryopreservation services depending on researchers needs. When deciding to cryopreserve a line, the researcher will need to choose if embryo or sperm freezing is the best option for them.

Situation	Best Approach	Minimal Approach	Comment
Single genetic modification (on congenic background)	Sperm	Sperm	Fast, economical (free service under the BVS contingency programme), only needs 2 male donors. Rederivation for certain strains doesn't work well by IVF; If you use a strain different from C57BL/6, C57BL/6 x CBA F1 or CD1, please get in touch to see if rederivation by IVF is an option for your strain.
2 or more genetic modifications	Embryo	Sperm	Additional breeding upon cryorecovery required when sperm cryopreservation is chosen.
Genetic background needs to be maintained (if not congenic)	Embryo	Embryo	Embryo cryopreservation is the only way a non-congenic background can be maintained.
Line is on an unusual background	Embryo	Embryo	Embryo cryopreservation is the only way an unusual background can be maintained.
X-linked mutation	Embryo	Sperm	Sperm cryopreservation is possible, but 50% of sperm won't carry the allele.
Y-linked mutation	Sperm	Sperm	Embryo cryopreservation is possible, however not recommended (as none of the female embryos will carry the allele).
Rat	Embryo	Embryo	Rat sperm can be frozen, however rat IVF or ICSI are not currently available at CTC.

Archiving your strain

If you anticipate a high demand for your strains from collaborators, or you'd like to archive your strain at an independent location, you should consider the free-of-charge (shipping costs only) archiving services offered by the European Mouse Mutant Archive (EMMA).