Comparison of gene transcription in cloned bovine embryos produced by different nuclear transfer techniques.

The efficiency of animal production using cloning technology is still relatively low and research to determine a more efficient nuclear transfer procedure is ongoing. One approach which may be informative in assessing the viability of nuclear transfer embryos is the analysis of embryonic gene expression. Using RT-PCR techniques we have previously detected the aberrant expression of FGF4, FGFr2 and IL6 in a significant proportion of bovine granulosa cell-derived nuclear transfer embryos, which correlated with a limited developmental potential in vivo. In order to analyse the effect of different donor cell nuclei on embryonic gene expression we have now analysed the expression of these genes in nuclear transfer embryos reconstructed with fetal epithelial cell nuclei. In addition, we have compared the expression of these genes in bovine nuclear transfer embryos produced by cell fusion or direct injection with variations in the timing of oocyte activation. In all nuclear transfer embryos analysed, FGFr2 and IL6 transcripts were detected at a similar rate to that in IVF embryos. However, the absence of FGF4 transcripts was again evident in a large proportion of nuclear transfer embryos and most significantly in those embryos whose development was activated almost immediately following the transfer of the donor nucleus. The results demonstrate the effects that different donor cell lines and different nuclear transfer procedures may have on the expression of developmentally important genes in nuclear transfer embryos. Copyright 2001 Wiley-Liss, Inc.