FIG. 2.

A) Severe reduction in fertility in Usp2 −/− males. Male Usp2 −/− mice or their HT or +/+ littermates were mated with CD1 females starting at age 6 wk for either 5 mo (one +/+ and one −/− male studied) or 6 wk (two +/+, one HT, and three −/− males studied). The female mouse was changed each week. Indicated are the number of litters sired and the average litter sizes. Shown are means ± SEM. Similar defect also seen with C57BL/6 females (data not shown). B) Reduction in fertility is not due to inability to inseminate. Male Usp2 −/− or +/+ mice were mated with CD1 females who were examined for the presence of a vaginal plug each day. Although percentage of plugging is similar with Usp2 +/+ or −/−, litter number and size are severely reduced in Usp2 −/−. C) Fertilization rate tested using superovulated females. Male Usp2 −/− or +/+ mice were each mated with two CD1 females who had been hormonally superovulated. The next day, females were killed, the eggs were harvested and cultured, and the number of fertilized eggs was counted. Usp2 −/− males yielded only 12% of the number of fertilized eggs obtained with Usp2 +/+ males. D) Usp2 −/− females have normal fertility. Usp2 +/+ or −/− females (both mixed sv129/C57BL6) were mated with Usp2 +/+ CD1 males. Litters were readily obtained with each genotype. Indicated are mean litter sizes.