Expression Profile of Developmentally Important Genes in preand peri-Implantation Goat Embryos Produced In Vitro

Little is understood about the regulation of gene expression during early goat embryo development. This study investigated the expression profile of 19 genes, known to be critical for early embryo development in mouse and human, at five different stages of goat in vitro embryo development (oocyte, 8-16 cell, morula, day-7 blastocyst, and day 14 blastocyst).

In this experimental study, stage-specific profiling using real time-quantitative polymerase chain reaction (RT-qPCR) revealed robust and dynamic patterns of stage-specific gene activity that fall into four major clusters depending on their respective mRNA profiles.

The gradual pattern of reduction in the maternally stored transcripts without renewal thereafter (cluster-1: Lifr1, Bmpr1, Alk4, Id3, Ctnnb, Akt, Oct4, Rex1, Erk1, Smad1 and 5) implies that their protein products are essential during early cleavages when the goat embryo is silent and reliant to the maternal legacy of mRNA. The potential importance of transcription augment at day-3 (cluster-2: Fzd, c-Myc, Cdc25a, Sox2) or day- 14 (cluster-3: Fgfr4, Nanog) suggests that they are nascent embryonic mRNAs which intimately involved in the overriding of MET or regulation of blastocyst formation, respectively. The observation of two expression peaks at both day-3 and day-14 (cluster-4: Gata4, Cdx2) would imply their potential importance during these two critical stages of preand periimplantation development.

Evolutionary comparison revealed that the selected subset of genes has been rewired in goat and human/goat similarity is greater than the mouse/goat or bovine/goat similarities. The developed profiles provide a resource for comprehensive understanding of goat preimplantation development and pluripotent stem cell engineering as well.