Abnormal gene expression in extraembryonic tissue from cloned porcine embryos.

The birth rate of cloned animals following somatic cell nuclear transfer (SCNT) is very low and the surviving animals have various developmental defects. We compared the morphology and transcriptional profile of extraembryonic tissue from three 26-d old SCNT pig fetuses with that from control fetuses. Transcriptional profiling using long-oligonucleotide microarray technology revealed 34 genes that were differentially expressed between the three groups. The differential expression of several genes involved in translational regulation was confirmed by real-time quantitative PCR and Western blot analysis. Interestingly, the expression of a translational inhibition-related gene encoding a eukaryotic translation initiation factor 4E-binding protein was significantly elevated in the SCNT samples. We concluded that the low birth rate of cloned animals could be related to abnormal expression of translational regulators in extraembryonic tissue during early pregnancy.