Transforming growth factors-α and -β expression in fertilized and parthenogenetic pre-implantation mouse embryos: RNA detection with fluorescent in situ hybridization.

Transforming growth factor (TGF)-α and -β are expressed in pre-implantation embryos and could play an important role in development. Usually, gene expression is studied using reverse transcription-polymerase chain reaction (RT-PCR) but here, we developed a fluorescent in situ hybridization (FISH) procedure applied on whole embryos that were spread and fixed on slides after hypotonic shock. This procedure allowed a rapid and specific detection of mRNA. For the first time, this technique was applied successfully to TGF-α, TGF-β1 and TGF-β2 on parthenogenetic embryos (maternal genome only) and fertilized controls (maternal and paternal genomes). TGF-β1 and β2 mRNA both appeared at the late 8-cell stage and increased in morulae and blastocysts. TGF-α expression increased from the 2-cell stage to the blastocyst stage. Patterns of expression were similar in parthenogenetic and caryogamic embryos, suggesting that no maternal imprinting exists for these three genes.