FIGURE 2.

Impaired sperm migration from the uterus into the oviduct in Calr3^−/− mice. A, pregnancy rate (pregnancy/vaginal plug formation) presented as a percentage. Calr3^−/− males copulated normally but failed to induce pregnancy. Four males were examined in each group. The total number of plugs observed is indicated in parentheses. B–D, sperm migration assay. The oviduct with the uterus was removed 2 h after coitus, and frozen sections containing the uterotubal junction (red dashed line in B) were prepared. Although wild-type sperm were observed in the uterine part and the uterotubal junction, Calr3^−/− sperm were observed only in the uterine part and not in the uterotubal junction (C and D). The boxes in C are magnified in D. Arrows indicate sperm. The sections were stained with hematoxylin and eosin.