FIG. 4.

Impaired meiotic progression in Ubb^−/− mouse oocytes in vitro. (A) Delayed and impaired GVBD (left) and absent polar body extrusion (right) in oocytes isolated from Ubb^−/− mice and allowed to undergo spontaneous maturation in vitro (n = 3 to 4/genotype). (B) Spindle morphologies of in vitro-matured oocytes. Oocytes were labeled with antibody to α-tubulin (green) and with DAPI (blue). Out of 19 oocytes examined, 2 formed a normal-appearing spindle, 7 formed aberrant spindles, and 10 failed to form any spindle.