The transcription factors, including OCT4, NANOG, and SOX2, played crucial roles in the maintenance of self-renewal and pluripotency in embryonic stem cells (ESCs). They expressed in preimplantation mammalian development with spatio- temporal pattern and took part in regulation of development. However, their expression and roles in goat had not been reported. In the present study, the expression of OCT4, NANOG, and SOX2 in goat preimplantation embryos both in vivo and in vitro were detected by real-time RCR and immunofluorescence. For in vivo fertilized embryos, the transcripts of OCT4, NANOG, and SOX2 could be detected from oocytes to blastocyst stage, their expression in morula and blastocyst stages was much higher than other stage. OCT4 protein was detected from oocyte to blastocyst, but the fluorescence was more located-intensive with nuclei from 8-cell stage, its expression present in both inner cell mass (ICM) and trophoblast cells (TE) at blastocyse stage. NANOG protein was similar to OCT4, the signaling of fluorescence completely focused on cell nuclei, while the SOX2 firstly showed nuclei location in morula. Comparing to in vivo fertilized embryo, the mRNA of these three transcription factors could be detected at 8-cell stage in parthenogenetic embryos (in vitro). Thereafter, the expressional level rose gradually along with embryo development. The locations of OCT4 and NANOG proteins were similar to in vivo fertilized embryos, and they located in cell nuclei from morula to blastocyst stage, while SOX2 protein firstly could be detected in cell nuclei at 8-cell stage. These differences suggested that OCT4, NANOG, and SOX2 played different function in regulating development of goat preimplantation embryos. These results may provide a novel insight to goat embryo development and be useful for goat ESCs isolation.

Nanog, Oct4 and Sox2 are important transcription factors that are expressed in embryonic stem (ES) cells or embryoniccarcinoma (EC) cells, but in most cases they are absent in somatic cells. These factors play a key role to maintain embryonic stemcell self-renew and pluripotency. Down-regulation of Nanog and Sox2 gene expression can change multiple gene expressionpatterns and signal transduction pathways, and will initiate ES cell differentiation. This study was designed to select theefficient small interfering RNA (siRNA) fragments that inhibit Nanog and Sox2 gene expression in mouse J1 ES cells and P19 ECcells. Among synthesized siRNAs we screened out the siRNA N301 for Nanog and siRNA S720 for Sox2, which not only downregulatedof Nanog and Sox2 gene expression, but also interfered embryoid bodies formation. Our study provided the definedsiRNA fragments that could be used to investigate the epigenetic function of Nanog and Sox2 genes.