Fig. 4.
Effect of myeloid-selective Usp2 knockout on the motility, hyperactivation, and capacitation of frozen–thawed sperm. Sperm of myeloid-selective Usp2 knockout mice (mKO) and Usp2fl/fl mice (fl/fl) were subjected to the freeze–thaw process. a The morphology of the epididymal sperm. Scale bars represent 50 µm. Representative microscopic images were obtained from five mice. b The viability of the epididymal sperm. c Sperm motility assessed by CASA. Total motility, progressive motility, straight-line velocity (VSL), curvilinear velocity (VCL), amplitude of lateral head displacement (ALH), and beat-cross frequency (BCF) of sperm were evaluated. d The proportion of hyperactivated sperm. K-means clustering was used to analyze the CASA data. Hyperactive sperm belonged to the cluster with high VCL and low linearity, as shown in Supplementary Fig. 8. e The proportion of capacitated sperm. Capacitation was determined by CTC staining. Approximately 200 (b, e), 300 (c), 340 (d, mKO), or 420 (d, fl/fl) sperm from each mouse was used for analysis. Data are shown as means ± SD of five (b, e) or six (c, d) mice. *P < 0.05 vs. Usp2fl/fl mice (c–e). The P values are also shown in the graphs (b, c)