Effects of MKlp2 disruption on polar body extrusion in mouse oocytes. (A) Oocytes failed to extrude polar bodies after MKlp2 disruption by paprotrain treatment, whereas after rescue, oocytes developed to the MII stage. Circles in control and rescued oocytes show oocytes that reached the MII stage, whereas circles in treated oocytes show that they were arrested at an earlier stage. (B) Rates of polar body extrusion after MKlp2 disruption. *significantly different (p < 0.05). (C) Rates of oocytes remaining at the TI and MII stage after MKlp2 disruption and after rescue. *significantly different (p < 0.05). (D) Time-lapse microscopy of maturing oocytes after MKlp2 disruption. For controls, oocytes extruded polar bodies; whereas treated oocytes were arrested at the MI stage.