Pre-anaphase centromere dynamics during meiosis I in mrc1 and moa1 mutants.
(A) Pre-anaphase dynamics of the spindle pole and centromere (cen2) at meiosis I, and changes in the distance between the spindle pole and the centromere and between the two spindle poles in mrc1, moa1, and rec8 mutants. Note that only one of the homologous centromeres is visualized in mrc1 rec12 and rec8 mutant cells. Horizontal bar: 50 s. Vertical bar: 2 µm. (B) Average centromere dissociation frequencies in mrc1, moa1, and rec8 mutant cells. The number of centromeres examined is shown in parentheses. +: no rec12 mutation. ND: not determined. Asterisks indicate dissociation frequencies that are statistically different from the frequency of wild type. * p<0.005; ** p<0.01. (C) Observation frequencies of centromeres at distinct positions in the spindle during the pre-anaphase stage. The positions of centromeres are shown based on their relative distance from the spindle center (d), as determined in Figure 4B. The number of examined positions is shown in parentheses. (D) Bipolar attachment of sister chromatids and expected observation frequencies of centromeres at distinct positions in the spindle. (E) Distance between homologous centromeres. The distance between homologous centromeres was measured at every time point in each strain, and an average distance is shown. When centromeres were dissociated, the distance between the nearest homologous pair of centromeres was measured. The asterisk indicates a distance statistically different from that of wild type (p<5×10−125). The number of distances examined is shown in parentheses. Right illustrations show models for spindle attachment of chromosomes and the resultant distance between the centromeres in wild-type, mrc1, and moa1 mutant cells. White arrows in all illustrations indicate forces exerted on chromosomes. Error bars in all graphs indicate standard deviations.