Abstract
Transgenic mouse embryos at the 2-cell stage were vitrified by the method described by Nakagata with slight modifications [J Mamm Ova Res 1989; 6: 23-26 (in Japanese)]. In vivo cryosurvival was examined by transferring the vitrified-warmed transgenic embryos into recipi-ents. A total of 107 embryos out of 118 (90.7%) were recovered normally after warming; 45.8% of the normal embryos developed to full term. When the integration pattern of the transgene into the host genome and its expression level were compared between offspring derived from vitrified and unvitrified (control) transgenic embryos, there was no significant alteration with respect to each parameter. From these results, it was indicated that the vitrification procedure we employed does not affect the expression level of the transgene or its integration pattern in chromosomal DNA.