Early morphological nuclear events and developmental capacity of embryos reconstructed with fetal fibroblasts at the M or G1 phase after intracytoplasmic nuclear injection in cattle.
We examined morphological nuclear events during the first cell cycle of bovine embryos reconstructed with somatic cells at the M and G1 phases (M-embryos and G1-embryos, respectively) by intracytoplasmic nuclear injection, and the subsequent development of these embryos in vitro and in vivo. Bovine fetal fibroblasts (BFFs) at the M or G1 phase were directly injected into enucleated oocytes, and activated immediately. Only half (48%) of the M-embryos extruded polar body-like cells (PBCs) at 6 h post injection (hpi). At 15 to 19 hpi, 54% of the M-embryos formed a single pronucleus-like nucleus. Nuclear envelope-breakdown, premature chromosome condensation and single nuclear clusters were observed in most of the G1-embryos (88%) within 30 min following the nuclear injection. At 15 to 19 hpi, single pronucleus-like nuclei were formed in most G1-embryos (83%). The potential of G1-embryos to develop to blastocysts was significantly higher than that of M-embryos (31% vs 16%). Three of five recipients following transfer of blastocysts derived from the G1-embryos became pregnant on Day 30, and one recipient delivered a calf. Our results indicate that almost a half of the M-embryos failed to extrude PBCs and that the G1-embryos developed to blastocysts at a higher rate than the M-embryos.
Ideta
Atsushi
A
ZEN-NOH Embryo Transfer Center, Kamishihoro, Hokkaido, Japan. ideta@zk.zennoh.or.jp
Urakawa
Manami
M
Aoyagi
Yoshito
Y
Saeki
Kazuhiro
K
D000818:Animals; D002417:Cattle; D002455:Cell Division / Q000502:physiology; D002467:Cell Nucleus / Q000502:physiology; D019976:Cloning, Organism / Q000379:methods* / Q000662:veterinary*; D047108:Embryonic Development / Q000502:physiology*; D005260:Female; D005347:Fibroblasts / Q000166:cytology*; D016193:G1 Phase / Q000502:physiology; D053652:Nuclear Transfer Techniques; D009865:Oocytes / Q000166:cytology / Q000502:physiology; D011247:Pregnancy; D011256:Pregnancy Outcome