BubR1-depletion impairs kinetochore-microtubule attachments. (A to C) At 8 h post-GVB D, control oocytes (A) and BubR1-depleted oocytes (B and C) were immunostained for tubulin, DNA and Mad2. (D to F) Control oocytes were cold-treated(9) and immunostained at 4 h post-GVBD (D) and 8 h post-GVBD (E). Note the change in spindle morphology afte r cold-treatment (compare A and E). BubR1-depleted oocytes were cold-treated and immunostained at 8 h post-GVBD (F) (n ≥ 20 oocytes per group). Note that chromosomes are extended although kinetochore-microtubule attachments are lacking (B and C), implicating direct contacts between microtubules and chromatin as demonstrated previously(15). Conversely, chromosomes become compacted when microtubules are lacking (F, white arrow).