Analysis of mRNA transcripts for insulin-like growth factor receptors and binding proteins in bovine embryos derived from somatic cell nuclear transfer.

The low efficiency of animal production using somatic cell nuclear transfer procedures is considered to be the result of an incomplete reprogramming of donor cell nucleus, which leads to abnormal expression of developmentally important genes. The objective of this study was to determine the abundance of gene transcripts of insulin-like growth factor (IGF)-related genes in cloned bovine embryos reconstructed with somatic cells. Single embryos derived from nuclear transfer reconstructed with somatic cells (NT-SC) or embryo blastomeres (NTEM), in vitro fertilization (IVF), in vivo production (Vivo), and parthenogenetic treatment (PA) were analyzed. The relative abundance of mRNA was examined by real-time PCR. Transcripts of the IGF-1 receptor (r) and IGF binding protein (BP)-2 were detected in all embryos, regardless of origin. IGF-IIr and IGFBP-3 transcripts signals in NT-SC embryos were detected with significantly lower frequencies of 25 and 50%, respectively. Although IGF-Ir and IGFIIr transcript levels were not significantly different in NT-SC, NT-EM, IVF, Vivo, and PA embryos, the relative abundance in individual embryos indicated large variation in NT-SC. IGFBP-2 and IGFBP-3 levels were high in the Vivo embryos compared with NT-SC, NT-EM, IVF, or PA embryos. These results suggest differences in levels of transcripts of IGF-related genes in the bovine embryos produced by NT compared with IVF, Vivo, and PA.