Cloning and Characterization of 3.1kb Promoter Region of the Oct4 Gene from the Fischer 344 Rat

Boron enhances early embryonic gene expressions and improves fetal development of rats

Boron is present as several different components in nature. Besides its industrial use, it is an essential element and is playing a very important role in the metabolism. In this study, it was aimed to determine the in vivo effects of boron on mRNA expression of HEX, NANOG, and OCT-3/4 genes in embryo and histological changes during fetal development. Therefore, totally 60 female rats were allocated into 5 equal groups. Experimental groups are as the followings; positive control (fed with standart rat diet), negative control (fed with boron free diet), low boron group (fed with boron free diet and given 0.04 μg boron/ml via gastric gavage), marginal boron group (fed with boron free diet and given 0.3 μg boron/ml via gastric gavage) and normal boron group (fed with boron free diet and given 2 μg boron/ml via gastric gavage). Experimental period was performed for 14 days. Embryos were collected after 4 days of mating and the expression and protein levels of early embryonic genes namely HEX, NANOG, and OCT-3/4 were determined by using Real-Time PCR. Also, 10-20 day embryo and fetus development were histologically determined. According to the results, mRNA expression and protein levels of early embryonic genes were increased in boron groups while decreased in boron deficient group. Histopathologically, tissue and organ developments were definitely observed in the boron groups. In conclusion, mRNA expression levels of early embryonic genes decreased in boron deficient group and boron has an important role for fetal development.

Evolutionary Conservation of pou5f3 Genomic Organization and Its Dynamic Distribution during Embryogenesis and in Adult Gonads in Japanese Flounder Paralichthys olivaceus

Octamer-binding transcription factor 4 (Oct4) is a member of POU (Pit-Oct-Unc) transcription factor family Class V that plays a crucial role in maintaining the pluripotency and self-renewal of stem cells. Though it has been deeply investigated in mammals, its lower vertebrate homologue, especially in the marine fish, is poorly studied. In this study, we isolated the full-length sequence of Paralichthys olivaceus pou5f3 (Popou5f3), and we found that it is homologous to mammalian Oct4. We identified two transcript variants with different lengths of 3′-untranslated regions (UTRs) generated by alternative polyadenylation (APA). Quantitative real-time RT-PCR (qRT-PCR), in situ hybridization (ISH) and immunohistochemistry (IHC) were implemented to characterize the spatial and temporal expression pattern of Popou5f3 during early development and in adult tissues. Our results show that Popou5f3 is maternally inherited, abundantly expressed at the blastula and early gastrula stages, then greatly diminishes at the end of gastrulation. It is hardly detectable from the heart-beating stage onward. We found that Popou5f3 expression is restricted to the adult gonads, and continuously expresses during oogenesis while its dynamics are downregulated during spermatogenesis. Additionally, numerous cis-regulatory elements (CRE) on both sides of the flanking regions show potential roles in regulating the expression of Popou5f3. Taken together, these findings could further our understanding of the functions and evolution of pou5f3 in lower vertebrates, and also provides fundamental information for stem cell tracing and genetic manipulation in Paralichthys olivaceus.

Investigating the functionality of an OCT4-short response element in human induced pluripotent stem cells

Pluripotent stem cells offer great therapeutic promise for personalized treatment platforms for numerous injuries, disorders, and diseases. Octamer-binding transcription factor 4 (OCT4) is a key regulatory gene maintaining pluripotency and self-renewal of mammalian cells. With site-specific integration for gene correction in cellular therapeutics, use of the OCT4 promoter may have advantages when expressing a suicide gene if pluripotency remains. However, the human OCT4 promoter region is 4 kb in size, limiting the capacity of therapeutic genes and other regulatory components for viral vectors, and decreasing the efficiency of homologous recombination. The purpose of this investigation was to characterize the functionality of a novel 967bp OCT4-short response element during pluripotency and to examine the OCT4 titer-dependent response during differentiation to human derivatives not expressing OCT4. Our findings demonstrate that the OCT4-short response element is active in pluripotency and this activity is in high correlation with transgene expression in vitro, and the OCT4-short response element is inactivated when pluripotent cells differentiate. These studies demonstrate that this shortened OCT4 regulatory element is functional and may be useful as part of an optimized safety component in a site-specific gene transferring system that could be used as an efficient and clinically applicable safety platform for gene transfer in cellular therapeutics.

Methylation of the Sox9 and Oct4 promoters and its correlation with gene expression during testicular development in the laboratory mouse

Sox9 and Oct4 are two important regulatory factors involved in mammalian development. Sox9, a member of the group E Sox transcription factor family, has a crucial role in the development of the genitourinary system, while Oct4, commonly known as octamer binding transcription factor 4, belongs to class V of the transcription family. The expression of these two proteins exhibits a dynamic pattern with regard to their expression sites and levels. The aim of this study was to investigate the role of de novo methylation in the regulation of the tissue- and site-specific expression of these proteins. The dynamics of the de novo methylation of 15 CpGs and six CpGs in Sox9 and Oct4 respectively, was studied with sodium bisulfite genomic DNA sequencing in mouse testis at different developmental stages. Consistent methylation of three CpGs was observed in adult ovary in which the expression of Sox9 was feeble, while the level of methylation in somatic tissue was greater in Oct4 compared to germinal tissue. The promoter-chromatin status of Sox9 was also studied with a chromatin immune-precipitation assay.

Inhibition of protein kinase C signaling maintains rat embryonic stem cell pluripotency

Embryonic stem cell (ESC) pluripotency is orchestrated by distinct signaling pathways that are often targeted to maintain ESC self-renewal or their differentiation to other lineages. We showed earlier that inhibition of PKC signaling maintains pluripotency in mouse ESCs. Therefore, in this study, we investigated the importance of protein kinase C signaling in the context of rat ESC (rESC) pluripotency. Here we show that inhibition of PKC signaling is an efficient strategy to establish and maintain pluripotent rESCs and to facilitate reprogramming of rat embryonic fibroblasts to rat induced pluripotent stem cells. The complete developmental potential of rESCs was confirmed with viable chimeras and germ line transmission. Our molecular analyses indicated that inhibition of a PKCζ-NF-κB-microRNA-21/microRNA-29 regulatory axis contributes to the maintenance of rESC self-renewal. In addition, PKC inhibition maintains ESC-specific epigenetic modifications at the chromatin domains of pluripotency genes and, thereby, maintains their expression. Our results indicate a conserved function of PKC signaling in balancing self-renewal versus differentiation of both mouse and rat ESCs and indicate that targeting PKC signaling might be an efficient strategy to establish ESCs from other mammalian species.

Embryonic stem cells induce pluripotency in somatic cell fusion through biphasic reprogramming

It is a long-held paradigm that cell fusion reprograms gene expression but the extent of reprogramming and whether it is affected by the cell types employed remain unknown. We recently showed that the silencing of somatic genes is attributable to either trans-acting cellular environment or cis-acting chromatin context. Here, we examine how trans- versus cis-silenced genes in a somatic cell type behave in fusions to another somatic cell type or to embryonic stem cells (ESCs). We demonstrate that while reprogramming of trans-silenced somatic genes occurs in both cases, reprogramming of cis-silenced somatic genes occurs only in somatic-ESC fusions. Importantly, ESCs reprogram the somatic genome in two distinct phases: trans-reprogramming occurs rapidly, independent of DNA replication, whereas cis-reprogramming occurs with slow kinetics requiring DNA replication. We also show that pluripotency genes Oct4 and Nanog are cis-silenced in somatic cells. We conclude that cis-reprogramming capacity is a fundamental feature distinguishing ESCs from somatic cells.

Could MDMA Promote Stemness Characteristics in Mouse Embryonic Stem Cells via mGlu5 Metabotropic Glutamate Receptors?

OBJECTIVE

Ecstasy, or 3, 4 (±) methylenedioxymethamphetamine (MDMA), is a potent neurotoxic drug. One of the mechanisms for its toxicity is the secondary release of glutamate. Mouse embryonic stem cells (mESCs) express only one glutamate receptor, the metabotropic glutamate receptor 5 (mGlu5), which is involved in the maintenance and self-renewal of mESCs. This study aims to investigate whether MDMA could influence self-renewal via the mGlu5 receptor in mESCs.

MATERIALS AND METHODS

In this expremental study, we used immunocytochemistry and reverse transcription-polymerase chain reaction (RT-PCR) to determine the presence of the mGlu5 receptor in mESCs. The expression of mGlu5 was evaluated after MDMA was added to mESCs throughout neural precursor cell formation as group 1 and during neural precursor cell differentiation as group 2. The stemness characteristic in treated mESCs by immunofluorescence and flow cytometry was studied. Finally, caspase activity was evaluated by fluorescence staining in the treated group. One-way ANOVA or repeated measure of ANOVA according to the experimental design was used for statistical analyses.

RESULTS

In this study mGlu5 expression was shown in mESCs. In terms of neuronal differentiation, MDMA affected mGlu5 expression during neural precursor cell formation (group 1) and not during neural precursor differentiation (group 2). MDMA (450 µM) induced a significant increment in self-renewal properties in mESCs but did not reverse 2-methyl-6(phenylethynyl) pyridine (MPEP, 1 µM), a non-competitive selective mGlu5 antagonist. Fluorescence staining with anti-caspase 3 showed a significant increase in the number of apoptotic cells in the MDMA group.

CONCLUSION

WE OBSERVED A DUAL ROLE FOR MDMA ON MESCS: reduced proliferation and maintenance of self-renewal. The lack of decreasing stemness characteristic in presence of MPEP suggests that MDMA mediates its role through a different mechanism that requires further investigation. In conclusion, despite being toxic, MDMA maintains stemness characteristics.

Derivation and characterization of embryonic stem cells lines derived from transgenic Fischer 344 and Dark Agouti rats

Rat embryonic stem cell (ESC) lines are not widely available, and there are only 2 lines available for distribution. Here, ESC lines were derived and characterized from Fischer 344 (F344) rats that express marker transgenes either β-galactosidase or human placental alkaline phosphatase (AP), nontransgenic F344 rats, and from Dark Agouti (DA) rats. The ESC lines were maintained in an undifferentiated state as characterized by colony morphology, expression of Oct4, Nanog, Sox-2, Cdx2, and Stella, staining for AP, and stage-specific embryonic antigen-1. Pluripotency was demonstrated in vitro by differentiation to embryoid bodies, followed by embryonic monsters. The Cdx2 expression by ESCs was unexpected and was confirmed via reverse transcriptase-polymerase chain reaction, immunocytochemistry. Pluripotency of ESCs was demonstrated in vivo by production of teratoma after an injection into F344 nontransgenic rats, and by an injection of male DA ESCs into F344 or Sprague-Dawley rat blastocysts and the generation of chimeric rats and germline contribution. ESCs from both F344 and DA contributed to chimeric rats, and one DA ESC line was proved to be germline competent. ESC sublines were created by transfection with a plasmid expressing enhanced green fluorescent protein (eGFP) under the control of a beta actin promoter and cytomegalovirus enhancer (pCX-eGFP) or by transfection with a plasmid expressing GFP under the control of a 3.1 kb portion of the rat Oct4 promoter (pN1-Oct4-GFP). In pN1-Oct4-GFP sublines, GFP gene expression and fluorescence were shown to be correlated with endogenous Oct4 gene expression. Therefore, these new ESC lines may be useful for tissue engineering and transplantation studies or for optimizing culture conditions required for self-renewal and differentiation of rat ESCs. While they made chimeric rats, further work is needed to confirm whether the transgenic F344 rat ESCs described here are germline-competent ESCs.