![Paternal chromosomes are spatially separated from maternal chromosomes during zygote meiosis.(A) Live imaging of chromosomes in an egg expressing mCherry-MBD-NLS during the fertilization process. Maximum-intensity Z projection of the chromosome signal is shown. Time is relative to anaphase onset. A time-lapse video is shown in Video 2. The zona pellucida was softened by treatment with glutathione (A–D and F). (B) Left: Angle between maternal chromosomes and sperm fusion site. Middle: Parameters and assumptions for the simulation in which sperm fuse randomly on the egg surface. Right: Comparison between experimental data and a simulation where sperm fuse randomly anywhere on the egg surface. Data include zygotes that were polyspermy (polyspermy rate was 40% of the fertilized eggs). Fisher’s exact tests were used to obtain P values, and Holm correction was used for the correction of multiple comparisons (P value of 0–30° is < 8 × 10−3. P values of other areas are >0.05 [ns]). The rate of fusion events was corrected by the surface area after the statistical test. (C) Trajectories of chromosomes during the fertilization process. Paternal chromosomes move along the periphery of the zygote. Right: Trajectory of paternal chromosomes, which fuse within 30 µm of maternal chromosomes. The values of the position of chromosomes were normalized by the length between the sperm fusion site and the center of the egg. Data include only zygotes that were monospermic (C–E). Arrowhead shows when paternal chromosomes rapidly moved out of the 30-µm region (C and E). (D) Displacement of paternal chromosomes from the sperm fusion site. (E) Distance between paternal and maternal chromosomes, which were closer after anaphase onset. (F) Left: Angle × time model in which the angular displacement has a correlation with the position of paternal chromosomes and the time from sperm fusion, with negative interactions of these variables. The time from sperm fusion is shown in the color scale. Right: Angular displacement of paternal chromosomes toward maternal chromosomes in the minute during sperm fusion to 20 and 40–80 min after anaphase onset. Welch’s t test was used to obtain the P value (P value of fusion to 20 min is <0.001). **, P < 0.01; ***, P < 0.001.](https://cdn.rupress.org/rup/content_public/journal/jcb/220/10/10.1083_jcb.202012001/4/jcb_202012001_fig1.png?Expires=1770885952&Signature=tySThYHYmMksyQ9Cyy59214YN9fFl4cUfyMI95tqwApzJpNt9TQ6qZl9YM4XETZcRnTXlrRJxLPqbXNH5xgw-BZRLGoFPVWyYaX-hR8y-ktZ1UfEt~900sjZUJ32etdOFxj4WurMIB1LCjAZghXE1kRcOgaqQ7txEGMlvYY~3-jQqqDKTBvk95yxF5kPwSNIRI-XX~n80VJf0zA2nVyvQkZ6UoP7JniLDmvFsOPoxiDtN8E-0Nn9YLeS15D4H0UdI1MlzpLTI8FbVd5GitLdS3LDyryRZma6kXLhW67-iTz1QRHev42Fwgxu1aYTtGN11VyUlfFxmR8MIjz9VIwPWw__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Paternal chromosomes are spatially separated from maternal chromosomes during zygote meiosis. (A) Live imaging of chromosomes in an egg expressing mCherry-MBD-NLS during the fertilization process. Maximum-intensity Z projection of the chromosome signal is shown. Time is relative to anaphase onset. A time-lapse video is shown in Video 2. The zona pellucida was softened by treatment with glutathione (A–D and F). (B) Left: Angle between maternal chromosomes and sperm fusion site. Middle: Parameters and assumptions for the simulation in which sperm fuse randomly on the egg surface. Right: Comparison between experimental data and a simulation where sperm fuse randomly anywhere on the egg surface. Data include zygotes that were polyspermy (polyspermy rate was 40% of the fertilized eggs). Fisher’s exact tests were used to obtain P values, and Holm correction was used for the correction of multiple comparisons (P value of 0–30° is < 8 × 10−3. P values of other areas are >0.05 [ns]). The rate of fusion events was corrected by the surface area after the statistical test. (C) Trajectories of chromosomes during the fertilization process. Paternal chromosomes move along the periphery of the zygote. Right: Trajectory of paternal chromosomes, which fuse within 30 µm of maternal chromosomes. The values of the position of chromosomes were normalized by the length between the sperm fusion site and the center of the egg. Data include only zygotes that were monospermic (C–E). Arrowhead shows when paternal chromosomes rapidly moved out of the 30-µm region (C and E). (D) Displacement of paternal chromosomes from the sperm fusion site. (E) Distance between paternal and maternal chromosomes, which were closer after anaphase onset. (F) Left: Angle × time model in which the angular displacement has a correlation with the position of paternal chromosomes and the time from sperm fusion, with negative interactions of these variables. The time from sperm fusion is shown in the color scale. Right: Angular displacement of paternal chromosomes toward maternal chromosomes in the minute during sperm fusion to 20 and 40–80 min after anaphase onset. Welch’s t test was used to obtain the P value (P value of fusion to 20 min is <0.001). **, P < 0.01; ***, P < 0.001.
