Cryopreservation of Mouse strains by sperm freezing and embryo freezing
- Our basic strategy is to freeze SPERM of each mouse line.
- At least for strains generated in-house, we test fertility by thawing sperm and performing a test-IVF (in-vitro fertilization) and culture to the blastocyst stage.
- Additionally, we freeze embryos (2-cell stage) for strains that were generated in-house and are homozygous or compound.
What do we need for sperm freezing?
We need 2 males (and maybe a third as backup), best between 3-8 month old, and proven breeders are preferred.
We need information about the background strain and the mutations (kind, genotype).
If you know the MGI-ID (Mouse Genome Informatics) of the mutation(s) it would also help a lot.
We freeze ~20 semen straws for each strain.
What do we need for embryo freezing?
Depending on their age we need 4-8 females to freeze homozygous embryos. Females at 3-4 weeks old respond best to hormones, but older ones can also be used.
We use IVF (in-vitro fertilization) to produce embryos for freezing. We use frozen/thawed sperm for the IVF. By this we can also see if the sperm survived freezing.
Depending on the strain and background the survival rate of frozen/thawed IVF-embryos can vary to a very large degree. Therefore we cannot guarantee that we can rederivate embryos from each single strain we freeze.
Since 2017 we use media from CosmoBio for freezing (FERTIUP®) and IVF(CARD®).