Knockdown of gene expression by antisense morpholino oligos in preimplantation mouse embryos cultured in vitro.

Knockdown of gene expression by antisense morpholino oligos (MOs) is a simple and effective method for analyzing the roles of genes in mammalian cells. Here, we demonstrate the efficient delivery of MOs by Endo-Porter (EP), a special transfection reagent for MOs, into preimplantation mouse embryos cultured in vitro. A fluorescein-labeled control MO was applied for monitoring the incorporation of MOs into developing 2-cell embryos in the presence of varying amounts of EP and bovine serum albumin. In optimized conditions, fluorescence was detected in 2-cell embryos within a 3-h incubation period. In order to analyze the validity of the optimized conditions, an antisense Oct4 MO was applied for knockdown of the synthesis of OCT4 protein in developing embryos from the 2-cell stage. In blastocysts, the antisense Oct4 MO induced a decrease in the amount in OCT4 protein to less than half. An almost complete absence of OCT4-positive cells and nearly complete disappearance of the inner cell mass in the outgrowths of blastocysts were also noted. These phenotypes corresponded with those of Oct4-deficient mouse embryos. Overall, we suggest that the delivery of MOs using EP is useful for the knockdown of gene expression in preimplantation mouse embryos cultured in vitro.

Exogenous expression of homeoprotein EGAM1N prevents in vitro cardiomyogenesis by impairing expression of T and Nkx2.5, but not Mef2c, in mouse embryonic stem cells.

Generation of multiple cell types from embryonic stem (ES) cells and induced pluripotent stem cells is crucial to provide materials for regenerative medicine. EGAM1N has been found in preimplantation mouse embryos and mouse ES cells as a functionally unclassified homeoprotein. Recently, we reported that expression of EGAM1N suppressed the in vitro differentiation of ES cells into progenitor cells that arise in early embryogenesis. To clarify the effect of EGAM1N on terminal differentiation, embryoid bodies (EBs) were prepared from ES cells expressing exogenous Egam1n. In EBs expressing Egam1n, cardiomyogenesis was inhibited by impairing the expression of crucial transcription factors Brachyury T and Nkx2.5 in the generation of mesoderm and cardiomyocytes, respectively. Expression levels of Mef2c, another crucial gene for cardiomyogenesis, were unaffected. Conversely, the expression levels of Gata6 and Plat, markers for the primitive endoderm lineage, and Cdx2, a marker for the trophectoderm lineage, were increased. These results suggested that certain cell populations in EBs expressing Egam1n preferentially differentiated to such cell lineages. Our results suggest that EGAM1N not only affects the generation of progenitor cells during early embryogenesis, but also the progression of terminal differentiation, such as cardiomyogenesis, in mouse ES cells.

Partial inhibition of differentiation associated with elevated protein levels of pluripotency factors in mouse embryonic stem cells expressing exogenous EGAM1N homeoprotein.

We previously reported that transcripts encoding the homeoprotein EGAM1N are expressed in preimplantation mouse embryos and embryonic stem (ES) cells, and the exogenous expression of EGAM1N inhibits the differentiation of ES cells. In order to clarify the relationship between the inhibition of differentiation and EGAM1N, we generated mouse MG1.19 ES cells stably expressing EGAM1N. Control transfectants with an empty vector formed relatively flattened cell colonies similar to those observed in parental MG1.19 cells. In contrast, Egam1n transfectants formed tightly aggregated cell colonies with increased localization of CDH1 at cell-to-cell interfaces. The protein levels of pluripotency factors, including TBX3 and SOX2, were also increased. The expression of Tbx3 transcripts was induced, although the level of Sox2 transcripts was almost unchanged. The expression of EGAM1N resulted in no obvious changes in the expression of genes encoding receptors, protein kinases, transcription factors, and their encoded proteins involved in the LIF-STAT3 signaling pathway. Alkaline phosphatase activity, a marker for the undifferentiated state, in Egam1n transfectants was exhibited in a clonal proliferation assay. When differentiation of Egam1n transfectants was induced, progression was prevented with increases in transcript levels of Pou5f1, Sox2, Nanog, Klf4, Tbx3, and their encoded proteins. However, Egam1n transfectants formed relatively flattened-cell layers as observed in the control, indicating that the expression of EGAM1N could not maintain LIF-independent self-renewal of ES cells. Overall, we suggest that expression of EGAM1N could inhibit differentiation, at least in part, by elevating the protein levels of pluripotency factors in MG1.19 ES cells.