A GROWTH-FACTOR PHENOTYPE MAP FOR OVINE PREIMPLANTATION DEVELOPMENT

The reverse transcription-polymerase chain reaction (RT-PCR) was used to determine the patterns of expression for several growth factor liga nd and receptor genes during ovine preimplantation development. Transc ripts for insulin-like growth factor (IGF)-I, IGF-II, and the receptor s for insulin and IGF-I were detected throughout ovine preimplantation development from the 1-cell to the blastocyst stage. Transforming gro wth factor alpha (TGFalpha) transcripts were also detected throughout ovine preimplantation development. The mRNAs encoding basic fibroblast growth factor (bFGF) were detected in all stages of the ovine preimpl antation embryo, although the relative abundance of this transcript co nsistently decreased from the 1-cell to the blastocyst stage, suggesti ng that it may represent a maternal transcript in early sheep embryos. Transcripts encoding ovine trophoblast protein (oTP) were detected on ly within blastocyst-stage embryos. Primary ovine oviduct cell culture s express the transcripts for IGF-II, IGF-I, TGFalpha, bFGF, TGFbeta1, and the receptors for insulin and IGF-I, suggesting that paracrine gr owth factor circuits may exist between the oviduct epithelium and the early ovine embryo. Transcripts for insulin, epidermal growth factor ( EGF), and nerve growth factor (NGF) were not detected in any stage of the ovine preimplantation embryo or within the oviduct cell preparatio ns. The expression of growth factor transcripts very early in mammalia n development would predict that these molecules fulfil a necessary ro le(s) in supporting the progression of early embryos through the preim plantation interval. Our future efforts will be directed to understand ing the nature of these putative regulatory pathways.