F-actin keeps paternal chromosomes away from maternal chromosomes following egg–sperm fusion. (A) Live imaging of F-actin and chromosomes using 3mEGFP_UtrCH and mCherry-MBD-NLS during the fertilization process. Maximum-intensity Z projection of F-actin and chromosome signals are shown. Time is relative to anaphase onset. A time-lapse video is shown in Video 7. A hole was made in the zona pellucida using a piezo-driven pipette without glutathione treatment (A–C). (B) Live imaging of chromosomes (mCherry-MBD-NLS) following treatment with DMSO or LatB. Time is relative to anaphase onset. A time-lapse video is shown in Video 8. (C) Distance between paternal chromosomes and maternal chromosomes, which are closer after anaphase onset following treatment with DMSO or LatB. Paternal chromosomes are frequently captured by maternal chromosomes when a sperm fuses to a site within the 30-µm region surrounding maternal chromosomes. (D) Distance between paternal chromosomes and maternal chromosomes in eggs in which sperm heads were injected underneath the NA region following treatment with DMSO or LatB. A time-lapse video is shown in Video 9.