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). We culture until 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 (but even older ones may be OK), 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®).