Changes in the mRNA transcripts of insulin-like growth factor ligand, receptors and binding proteins in bovine blastocysts and elongated embryos derived from somatic cell nuclear transfer.

The objective of this study was to determine changes in the transcription of insulin-like growth factor (IGF)-related genes in blastocyst (BC)- and elongated (EL)-stage embryos produced by nuclear transfer using somatic cells (NT-SC). Bovine BC (day 7)- and EL (day 15)-stage embryos were obtained from NT-SC or in vivo production (Vivo). The relative abundance of mRNA was examined by RT- real-time PCR. The transcript of IGF-II was only detected at the EL stage in both the NT-SC and Vivo embryos. The level of transcription of the IGF-I receptor (r) in the NT-SC embryos was decreased at the EL stage and was significantly (P<0.05) lower than at the BC stage. In contrast, the IGF-IIr levels did not differ significantly between the NT-SC and Vivo embryos, regardless of the developmental stage. IGF-binding protein (IGFBP)-2 levels were markedly decreased in the NT-SC and Vivo embryos at the EL stage (P<0.05). The IGFBP-3 level in Vivo was significantly (P<0.05) increased at the EL stage compared with at the BC stage. However, the IGFBP-3 levels in NT-SC embryos were unchanged and lower (P<0.05) than in the Vivo embryos at the EL stage. These results suggest that there are differences in the levels and changes in the transcription of IGF-related genes in bovine embryos produced by NT-SC compared with those produced by Vivo.