The developmental potential of the inner cell mass of blastocysts that were derived from mouse ES cells using nuclear transfer technology.

The present study examined the causes of the low developmental potential of enucleated oocytes that have received ES cells and consequent postnatal death of the young. The inner cell masses (ICM) of nuclear-transferred blastocysts or diploid blastocysts were injected into tetraploid blastocysts (group B) or nuclear-transferred tetraploid blastocysts (group C), respectively. The developmental potential of these groups was compared with tetraploid blastocysts injected with ICM of diploid blastocysts (group A). The potential of reconstituted blastocysts to develop into live young in group B increased slightly (5%) but was significantly lower than that in group A (45%). The rate of postnatal death of young in group B did not decrease. The implantation rate of reconstituted blastocysts in group C was very low and no live fetuses were obtained. The results of the present study indicate that the inferior potential of both ICM and trophectoderm cells of nuclear-transferred blastocysts underlies the low developmental rate of nuclear-transferred oocytes receiving ES cells and the higher rate of postnatal death of ES cell-derived young.