Expression Pattern of Oct-4 in Preimplantation Embryos of Different Species

Abstract

POU transcription factors are involved in transcriptional regulation during early embryonic development and cell differentiation. Oct-4, a member of this family, has been shown to be under strict regulation during murine development. The expression of Oct-4 correlates with the undifferentiated cell phenotype of the mouse preimplantation embryo. In this study, expression of a gene construct consisting of selected parts of the region upstream from the murine Oct-4 gene as promoter/enhancer, enhanced green fluorescent protein (EGFP) as reporter and the five exons of the murine Oct-4 gene (GOF18-delta PE EGFP) was evaluated in murine, porcine, and bovine preimplantation embryos. For comparison, expression of the endogenous Oct-4 gene was also analyzed in all three species by immunocytochemistry. The transgene construct was microinjected into zygotes cultured in vitro to various developmental stages. The EGFP fluorescence was visualized in developing embryos by excitation with blue light at different days following microinjection and showed similar expression patterns in all three species. Most embryos displayed a mosaic pattern of transgene expression. The EGFP fluorescence was not restricted to the inner cell mass (ICM) but was also seen in trophoblastic cells. An affinity-purified polyclonal antibody specific to Oct-4 was used for immunocytochemical analysis of in vivo- and in vitro-derived bovine and porcine blastocysts and also of in vivo-derived murine blastocysts. In the in vivo-derived murine embryos, Oct-4 protein was detectable in the ICM but not the trophectoderm, whereas in porcine and bovine blastocysts, derived in vivo or in vitro, Oct-4 protein was detected in both the ICM and the trophectoderm. Thus, in the two large animal species, Oct-4 expression from the endogenous gene was clearly not restricted to the pluripotent cells of the early embryo. These results show that Oct-4 regulation differs between these species and that the presence of Oct-4 protein may not be sufficient for selection of undifferentiated cell lines in domestic animals.

Cheetah interspecific SCNT followed by embryo aggregation improves in vitro development but not pluripotent gene expression

“…In the mouse model, the OCT4 protein is down regulated in the TE of blastocysts and is expressed mainly in the ICM. On the other hand, bovine, porcine and primate blastocysts do not possess this distinctive pattern and also stain positive for OCT4 protein in TE (Kirchhof et al 2000, Harvey et al 2009). These differences in OCT4 distribution may be related to interspecies variations in the placenta and embryonic development.…”

“…In species other than the mouse, there are differences in genes regulating pluripotency and early differentiation, which may reflect differences in embryonic development (Kirchhof et al 2000, Kuijk et al 2008. Therefore, each species must be studied in order to understand the mechanism of maintaining pluripotency and differentiation in pre-implantation embryos, which may be useful to improve embryo development or establish stable embryonic stem cells lines in different species (Kirchhof et al 2000, Kuijk et al 2008.…”

Epigenetic regulation of gene expression in porcine epiblast, hypoblast, trophectoderm and epiblast-derived neural progenitor cells

“…Embryonic stem cells are in vitro cells derived from either the epiblast (in the human), [1][2][3] or ICM (in the mouse). 4 Several key genes are reported to be associated with the pluripotency of the ICM/epiblast, such as Oct4, [5][6][7][8][9][10][11] Sox2 12,13 and…”

Constraints to Progress in Embryonic Stem Cells from Domestic Species

“…However, in cattle and pig blastocysts, Oct-4 expresses both in the inner cell mass and in the trophectoderm, which suggests that the specification of the ICM and the trophectoderm compartments has to be accomplished by an alternative mechanism to that described in mice (i.e. lost of Oct-4 expression) [14]. Moreover, in porcine, the commitment of the epiblast and the primitive endoderm can not rely on a differential expression of NANOG and GATA-6, as the former has not been detected in porcine blastocysts [13].…”