Mating Mice

Abstract

In the process of creating and analyzing transgenic mice, matings between male and female animals are required for the following reasons:

• 1. To produce fertilized one-cell eggs for microinjection. Natural matings between mature females (over 6–7 wk of age) and stud males (over 7–8 wk of age) can be used to supply the one-cell eggs. Such matings can provide around 10 F2 eggs/mouse (from matings between CBA/J × C57B1/6 or C57B1/10 F1 male and female mice). However, it is preferable to mate the stud males with superovulated immature females. Such regimes can increase the yield of eggs per animal three- to fivefold, depending on the strain of mouse used.

• 2. To prepare 0.5-d postcoitum (pc) pseudopregnant recipient females to act as surrogate recipient mothers for microinjected one-cell eggs.

• 3. To maintain stocks of normal and transgenic animals. It is beyond the scope of this chapter to describe the animal husbandry techniques required to maintain a large breeding colony of normal or transgenic mice. Suffice to say that in most circumstances, colonies are expanded by the encouragement and meticulous monitoring of natural matings. However, it should be noted that an unusually large number of transgenic strains have reproductive defects. This can be a consequence of a variety of lesions, ranging from gross gonadal dysfunction to behavioral problems. It is sometimes neccessary to intervene in order to maintain and expand a transgenic line. Such intervention might entail either superovulation of a female transgenic mouse or in vitro fertilization using either or both transgenic eggs and sperm (Chapter 22).