Onset of the first S-phase is determined by a paternal effect during the G1-phase in bovine zygotes.
The aim of this study was to characterize the respective influences of the paternal and the maternal components on the timing of the first S-phase in the bovine zygote. In vitro-matured oocytes were fertilized in vitro with sperm conferring a high blastocyst rate (embryos of group 1) or a low blastocyst rate (embryos of group 2). Resulting zygotes were either allowed to develop in vitro to the blastocyst stage or exposed to 5'-bromo-2'-deoxyuridine in order to characterize the timing of their first S-phases. Timing of pronuclear formation was similar in the two groups, but the onset of S-phase and the first cleavage occurred earlier in group 1 than in group 2. We also showed that the length of the S-phase represented 30% of the first cell cycle in group 1 and 20% in group 2. Differences in times of onset of the first S-phase observed between embryo groups concerned both male and female pronuclei in a similar manner and were not dependent on the maternal component of the zygote. Our data demonstrated that the precocity of the onset of the first S-phase stemmed from a paternal control exerted during a transient period of the G1-phase.
Comizzoli
P
P
Muséum National d'Histoire Naturelle, Laboratoire de Conservation des Espèces Animales, 75012 Paris, France.
Marquant-Le Guienne
B
B
Heyman
Y
Y
Renard
J P
JP
D000818:Animals; D016590:Aphidicolin / Q000494:pharmacology; D001755:Blastocyst / Q000502:physiology; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002417:Cattle; D002467:Cell Nucleus; D004256:DNA Polymerase I / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005307:Fertilization in Vitro; D016193:G1 Phase; D008297:Male; D009865:Oocytes / Q000502:physiology; D016196:S Phase; D013997:Time Factors; D015053:Zygote / Q000166:cytology*
D004791:Enzyme Inhibitors; D016590:Aphidicolin; D004256:DNA Polymerase I; D001973:Bromodeoxyuridine