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​Effect of activation time on the nuclear remodeling and in vitro development of nuclear transfer embryos derived from bovine somatic cells. CHOI, JONG-YEOB​ 

Korea J. Animal Reprod. 춘계학술대회 Proceedings: 6, 2002. 6. 14-16

Effect of activation time on the nuclear remodeling and in vitro 

development of nuclear transfer embryos derived from

bovine somatic cells

CHOI, JONG-YEOB

Department of Animal Science

Graduate School, Kangwon National University

Abstract

This study was conducted to investigate the effect of recipient activation 

time on the nuclear remodeling, chromatin structure, pronuclear formation 

and in vitro development of bovine nuclear transfer embryos derived from 

adult ear skin cells. Somatic cells were transferred to enucleated oocytes 

after quiescent treatments by serum starvation or growth to confluency. 

Nuclear transfer embryos were activated with a combination of Ca++-

ionophore and cycloheximide at 1, 1.5, 2, 2.5, 3, and 5 h after 

electrofusion. After fusion, number of embyos with condensed chromsomes of 

Ⅰ(early PCC) and Ⅱ(full PCC) types increased in embryos activated within 

2 h, while Ⅲ(elongated PCC) and Ⅳ(scattered PCC) types increased in 

embryos activated after 2.5 h. The proportion of embryos with single 

chromatin clump (40.6-56.7%) was significantly increased when nuclear 

transfer embryos were activated within 2.5 h after fusion compared to that 

of embryos were activated at 3 (22.3%) and 5 h(0.0%) after fusion(P<0.05). 

Developmental rate to the blastocyst stage significantly higher in embryos 

activated within 2 h after fusion(17.3-21.7%) compared to that of embryos 

activated at 2.5 to 5 h after fusion(P<0.05). Proportion of embryos with 

normal chromosome constitutions decreased with prolongation of activation 

time. In nuclear transfer embryos at 5 h after fusion, pronuclear membrane 

formation was restricted and polar body extrusion was increased. From the 

present result, it is suggested that activation time after fusion can 

affect nuclear remodeling, chromatin structure, chromosome constitution 

and in vitro development of bovine nuclear transfer embryos. Activation 

within 2 h after fusion can enhance the in vitro development of nuclear 

transfer embryos derived from bovine adult ear skin cells.