The present study investigated the nuclear remodeling, development potential with telomerase activity and transcription level of X-linked genes (ANT3, HPRT, MeCP2, RPS4X, XIAP, XIST and ZFX) in the bovine somatic cell nuclear transfer (SCNT) embryos using two different fusion and activation methods. Female adult fibroblasts were injected into perivitelline space of in vitro matured oocytes. The oocyte-nucleus complexes were fused and followed by immediately either activated (Group 1), or activated at 1 h post-fusion (hpf) (Group 2), respectively. The incidence of normal premature chromosome condensation (PCC) at 1 hpf was slightly increased in the Group 2, compared to those of Group 1, but there was no significant (p<0.05) difference. The incidence of normal pronucleus (PN) and chromosome spread at 5 and 18 hpf were significantly (p<0.05) higher in the Group 2 than those of Group 1. The cleavage rate to 2-cell stage, developmental rate to blastocyst stage, and the mean number of total and ICM cell numbers were significantly (p<0.05) higher in the Group 2, compared to those of Group 1. Level of telomerase activity was significantly (p<0.05) higher in the SCNT blastocysts of Group 2, compared to those of Group 1. Transcript levels of HPRT, MeCP2 and XIST were not significantly (p<0.05) different between blastocysts of Group 1 and 2. However, transcript level of ANT3, RPS4X, XIAP and ZFX were significantly (p<0.05) up-regulated in the SCNT blastocysts of Group 2, compared to those of Group 1. Taken together, it is concluded that oocyte activation at 1 hpf induces the enhanced developmental potential by efficient nuclear remodeling and subsequent facilitation of the nuclear reprogramming of bovine SCNT embryos.

ABSTRACT   INTRODUCTION   MATERIALS AND METHODS    Media and Chemicals    Preparation of Donor Cells    Preparation of Recipient Cytoplasms    Nuclear Transfer and Oocyte Activation    In Vitro Culture of Embryos    Immunofluorescent Staining of Embryos    Absolutely Quantitative Analysis of Transcripts by RealTime RT-PCR    Relative-quantitative Telomerase Repeat AmplificationProtocol (RQ-TRAP)    Statistical Analysis   RESULTS    Developmental Potential of SCNT Embryos    Relative Telomerase Activity (RTA) of SCNT Embryos    Transcript Levels of X-linked Genes in SCNT Embryos   DISCUSSION   ACKNOWLEDGEMENTS   REFERENCES

• Byeong-Gyun Jeon(OBS/Theriogenology and Biotechnology, College of Veterinary Medicine, Institute of Animal Medicine)
• Gyu-Jin Rho(OBS/Theriogenology and Biotechnology, College of Veterinary Medicine, Research Institute of Life Science, Gyeongsang National University, Jinju 660-701, Korea) Corresponding author