Fig. 6.

Effect of myeloid-selective Usp2 knockout on the efficiency of in vitro fertilization. Frozen–thawed 4 × 10⁴ live sperm, which were isolated from myeloid-selective Usp2 knockout mice (mKO) and Usp2^fl/fl mice (fl/fl), were subjected to in vitro fertilization (IVF) using the ova of C57BL/6 mice. Approximately, 60 ova were used for an IVF series. a Dispersion of cumulus cells. Ova surrounded with cumulus cells were incubated with sperm from the mice for 0, 20, and 40 min. b Ova after 8 h incubation with sperm. Arrows and arrowheads represent polar bodies and pronuclei, respectively. c, d Incidence of polar bodies (c) or pronuclei (d) in ova after incubation with sperm. Representative images of seven IVF series are shown (a, b). Scale bars represent 50 (a), or 20 (b) μm. Data are shown as means ± SD of seven male mice (c, d). *P < 0.05 vs Usp2^fl/fl mice (d). P value is also shown (c)