Delivery of microinjected eggs to surrogate mothers by oviduct transfer.

Following the microinjection procedure, the eggs must be transferred to pseudopregnant (0.5 d pc) recipient mothers. Embryos from the one-cell through the morula stage (0.5-2.5 d pc) are transferred into the ampullae by a procedure called an oviduct transfer, described herein. The oviduct transfer is preferably performed on the same day as the microinjections or, alternatively, on the following day. The latter timing will allow the. experimenter to observe whether injected eggs have developed to the two-cell stage, although it is preferable to minimize the time in culture. The number of eggs transferred to recipients should be targeted to produce a litter size of five to ten. In practice, the number of eggs required to achieve this number will depend on the competence of the experimenter and other factors, such as the quality of the DNA preparation (see Chapter 11). A suitable number of eggs delivered to each recipient mouse is 30. Oviduct transfer is not an easy technique, and novice experimenters are advised to practice first on cadavers, until they are happy with the procedure. A convenient dye may be used in place of eggs to visualize correct delivery of the pipet contents into the ampulla.