Fig. 1: Sperm represses histone mobility in both parental PNs.

a, b Changes in histone mobility during the early and mid-stages of ICSI and parthenogenetically activated zygotes. zFRAP analysis was performed at 4, 6, and 8 hpi or hpa. A recovery curve indicating the average fluorescence recovery rate is shown (a). The average mobile fraction (MF) is shown as a gray bar (b). Single dots indicate the MF score of each male and female pronuclei (mPN, fPN), respectively. Blue, mPN; pink, fPN-4h; orange, fPN-6h; and red, fPN-8h. For parthenogenetic (partheno)-zygotes with 2PN, the average MF score is shown. Error bar indicates the standard error (SE). The examined number of embryos (n) = 34, 36, 35, 28, 29, 28, respectively. c mPN was enucleated at 4 hpi/hpa from ICSI- and ROSI-zygotes. Two PN partheno-zygotes were prepared as controls. The remaining fPN was subjected to zFRAP analysis at 8 hpi/hpa. n = 24, 37, 30, respectively. d Illustration of the preparation of 1PN-zygotes. e Fluorescence images of each single PN: sperm-derived mPN (sp-mPN), spindle transfer-derived fPN (spt-fPN), and round spermatid-derived mPN (rs-mPN). f Average MF scores of 1PN-ICSI, -ROSI, and -spt-partheno. n = 64, 45, 45, respectively. g Two sperm were injected into enucleated MII oocytes (upper-left). Sperm (sp) were stained with Hoechst 33342. Fluorescence images of PNs: 1♂ (2sp) and 2♂ (2sp) indicate the one and two male PN-zygotes injected with two sperm (2sp), respectively (upper right and lower left). Two sperm injected into un-enucleated MII oocytes (2♂ + 1♀; lower right). h Average MF scores of the zygotes shown in g. As a control, one sperm was injected into enucleated MII- (same as 1PN-ICSI in f; 1♂(1sp)) and normal ICSI-zygotes (1♂ + 1♀). Blue and red dots indicated mPN and fPN, respectively. n = 33, 28, 14, 12, 49, respectively. i Recovery curve of ROSI-, ELSI-, tICSI-, ICSI-, and iICSI-zygotes. n = 42,39, 34, 97, 47, respectively. j Recovery curve of androgenic zygotes prepared by co-injection of sperm and round spermatid. n = 17, 17, respectively. The error bar indicates SE.