This study was carried out to examine the effect of postactivation treatment with latrunculin A (LatA), an actin polymerisation inhibitor, on in vitro and in vivo development of somatic cell nuclear transfer (SCNT) embryos derived from gene-modified Clawn miniature pig cells. After the fusion and activation, SCNT embryos were treated with or without a cytoskeletal inhibitor [LatA or 10.4 microM cytochalasin B (CB) for 2 h]. The cleavage rate was significantly higher (p < 0.05) in embryos exposed to 0.5 microM LatA than those in embryos exposed to CB and without a cytoskeletal inhibitor. Moreover, the blastocyst formation rate was significantly higher (p < 0.05) in embryos exposed to 0.5 or 1 microM LatA than those in embryos exposed to CB and without a cytoskeletal inhibitor. In addition, five fetuses were obtained from recipient uteri after transfer of embryos treated with 0.5 muM LatA. The results of this study show for the first time that postactivation treatment with LatA is effective to improve in vitro developmental capacity of gene-modified cloned miniature pig embryos and embryos treated with LatA have the ability to develop into fetuses.