Differential mRNA expression in rabbit in vivo pre-implantatory embryos

To study genes involved in embryo developmental competence and implantation in rabbits, the expression of a panel of genes related to pluripotency, angiogenesis, proliferation, apoptosis and differentiation were evaluated in late rabbit blastocysts. Thirty nulliparous does were used to obtain a total of 184 in vivo-derived blastocysts on days 4, 5 and 6 of development. The relative transcript abundance of vascular endothelial growth factor (VEGF), epidermal growth factor receptor 3 (erbB3), transforming growth factor β2 (TGF β2) and transcription factor OCT-4 were analysed from eight pools of each stage of development, using quantitative real-time reverse transcriptase-polymerase chain reaction (qrtRT-PCR). mRNA expression was detected for all genes in 4-, 5- and 6-day-old blastocysts, according to blastocyst growth and implantation proximity. Significant differences in OCT-4, VEGF and TGF β2 expression were observed between days of development. Results show a down-regulation of OCT-4 from the 4th day, contrasting with the up-regulation of VEGF and TGF β2 at 6-day-old blastocyst. These findings corroborate the importance of VEGF and TGF β2 in rabbit embryo development and implantation and suggest a possible regulator role of OCT-4 in embryonic angiogenetic factors. On the other hand, no differences were found for erbB3 expression. Therefore, the study of specific gene transcripts in rabbit blastocyst could provide novel embryo developmental competence markers and might be used as a new tool for further studies of embryo quality and in vitro development.