Fig 1

Cryopreservation: Preferred are early embryonic stages or spermatozoa (reprinted from Schenkel, Transgene Tiere 2. edition 2006, ISBN-10 3-540-28267-X, with friendly permit of Springer-Verlag, Heidelberg)

Transgenic mice exhibit an enormous scientific potential. The number of transgenic mice is increasing rapidly. Small populations, continued danger of loss, often a small success in breeding, the need to keep these mutants in stock and frequent interchange of transgenic mice between different facilities are some of the major problems when dealing with these unique mutants. This results in the need to keep also those lines alive which are out of current use. To handle these topics cryopreservation of early embryonic stages or of spermatozoa is a valuable tool. Both techniques keep some advantages and some disadvantages. Cryopreserved samples can be stored at -196°C unlimited. After a sufficient cryopreservation animals of a transgenic line must not be kept in stock.

What qualifies for cryopreservation?

  • Embryos in the 2-to 8-cell stage (oviduct stages): An embryo-transfer is needed following revitalisation leading in addition to rederivation. Higher stages are to be preferred since they bring a higher chance to receive living animals. Sometimes it needs much effort to obtain a sufficient number of embryos. Blastocysts can be cryopreserved, too, but are not protected against all infections. The animals obtained following revitalisation are genetically the same as the embryos cryopreserved.

  • Spermatozoa: Mature spermatozoa are available in most cases without limit, only a few donor animals are needed. However, following revitalisation an in-vitro-fertilisation (IVF) is required, a difficult technique not available for all genetic backgrounds. Here, the animals obtained following revitalisation are genetically depending on the thawed spermatozoa and on the oocytes subjected to IVF.

The cryopreservation technique to be used is to be chosen individually.

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