Expression of growth factor ligand and receptor genes in preimplantation stage water buffalo (Bubalus bubalis) embryos and oviduct epithelial cells

The temporal pattern of expression of genes for several growth factor ligan ds and receptors was examined in preimplantation water buffalo embryos and oviduct epithelial cells using RT-PCR. The identity of the resulting PCR pr oducts was confirmed by their expected size, restriction analysis, Southern blot hybridization and nucleotide sequence analysis. Preimplantation stage embryos from the one-cell to the blastocyst stage were derived after matur ation, fertilization and culture of oocytes in vitro. Expression of members of the insulin-like growth factor (IGF) family was observed predominantly in preimplantation stage embryos and oviduct epithelial cells. Similarly, t ranscripts encoding insulin and IGF-I receptors were detected at each stage of embryonic development. The mRNA transcript of the IGF-I receptor was no t detected in oviduct epithelial cells, but a prominent band corresponding to the insulin receptor was observed. Insulin and IGF-II mRNA were expresse d as maternal transcripts that were not detected at the two- to four-cell s tage but were present as zygotic transcripts at the eight-cell stage. Trans cripts encoding IGF-I were detected in oviduct epithelial cells, but were n ot observed in any of the preimplantation stage embryos. Transforming growt h factor (TGF) alpha and beta and epidermal growth factor mRNA transcripts were not detected in any of the preimplantation stage embryos. These result s indicate that IGF-I acts via a paracrine mechanism to promote growth and development of preimplantation water buffalo embryos. Similarly, IGF-II app ears to act through a heterologous autocrine mechanism via the IGF-I or the insulin receptor. Furthermore, the presence of TGF-alpha in oviduct epithe lial cells indicates that it may have a critical role during development.