Real-time reverse transcription-polymerase chain reaction analysis of translation initiation factor 1A (eIF-1A) in human and mouse preimplantation embryos

XPO1-Mediated EIF1AX Cytoplasmic Relocation Promotes Tumor Migration and Invasion in Endometrial Carcinoma

Dysregulation of eukaryotic translation initiation factor 1A, X-linked (EIF1AX), has been implicated in the pathogenesis of some cancers. However, the role of EIF1AX in endometrial carcinoma (EC) remains unknown. We investigated the EIF1AX expression in EC patients and assessed its tumorigenesis-associated function and nucleocytoplasmic transport mechanism in vitro and in vivo. The results indicated that the cytoplasmic EIF1AX expression showed a gradual increase when going from endometrium normal tissue, simple endometrial hyperplasia, complex endometrial hyperplasia, and endometrial atypical hyperplasia to EC, while vice versa for the nuclear EIF1AX expression. In addition, the cytoplasmic EIF1AX expression was positively correlated with histologic type, high International Federation of Gynecology and Obstetrics (FIGO) grade, advanced FIGO stage, deeper infiltration, high Ki67 index, and shorter recurrence-free survival in EC patients. In vitro, short hairpin RNA-mediated EIF1AX depletion or SV40NLS-mediated EIF1AX import into the nucleus in multiple human EC cells potently suppressed cell migration and invasion, epithelial-mesenchymal transition, and lung metastasis. Moreover, exportin 1 induced the transport of EIF1AX from the nucleus to the cytoplasm that could be inhibited by leptomycin B treatment or the mutation in the EIF1AX location sequence. These results demonstrate that cytoplasmic EIF1AX may play a key role in the incidence and promotion of EC, and thus, targeting EIF1AX or its nucleocytoplasmic transport process may offer an effective new therapeutic approach to EC.

Effects of pyruvate on early embryonic development and zygotic genome activation in pigs

Pyruvate is an important energy substance during early embryonic development of mammals. However, the underlying mechanisms of pyruvate during early embryonic development in pigs and its role in zygotic genome activation (ZGA) are not fully understood. Here, based on a previous RNA-seq dataset of porcine early embryos, we found that pyruvate metabolism-related genes started to be expressed at the 4-cell stage and that pyruvate metabolism-related genes were correlated with porcine ZGA marker genes. To determine the function of pyruvate in porcine embryos, in vitro fertilization (IVF) embryos were cultured in PZM-3 medium (control group); modified PZM-3 medium that only contains pyruvate and lactate plus salts (+P group); or modified PZM-3 medium lacking pyruvate (-P group). The 4-cell arrest rate at 72 h was significantly increased in the -P group compared to the +P group (P < 0.05). In addition, we observed that the reactive oxygen species (ROS) level was significantly increased and that the adenosine triphosphate (ATP) level was significantly (P < 0.05) decreased in the -P group compared to the +P group. Moreover, the expression of ZGA marker genes and SIRT1 protein in embryos was significantly decreased in the -P group compared to the +P group (P < 0.05). Furthermore, the acetylation level of H3K9 was significantly decreased (P < 0.05) and the methylation level of H3K9 was significantly increased (P < 0.05) in the -P group compared to the +P group. In summary, our findings demonstrate that pyruvate affects early embryonic development in pigs by promoting ZGA and reducing oxidative stress levels.

Lnc5926 is essential for early embryonic development in goats through regulation of ZSCAN4 and EIF1AX

Long noncoding RNAs (lncRNAs) are abundant in mammalian genomes and have been found to play important roles in many biological events. However, the mechanism by which lncRNAs regulate embryonic development remains to be fully elucidated. Here, we investigated the function of the lncRNA, TCONS_00135926 (referred to as lnc5926), through knockdown and overexpression experiments in goat early embryos. Lnc5926 expression at the eight-cell embryonic stage was significantly higher than that at other stages, which was consistent with the pattern of embryonic genome activation (EGA) gene expression. The blastocyst rate after lnc5926 knockdown in eight-cell embryos was significantly lower than that in the control group (0.2% vs. 17.1%, p < 0.05), whereas the cleavage rate was not affected (71.9% vs. 75.1%, p ˃ 0.05). After knockdown or overexpression of lnc5926 in embryos, we measured expression levels of the potential target genes, STAM, HACD1, UBL5, MIOX, ELF1, and the key EGA genes, ZSCAN4 and EIF1AX. Only ZSCAN4 and EIF1AX were significantly downregulated after lnc5926 knockdown, and this effect was reversed by lnc5926 overexpression. We conclude that lnc5926 plays an essential role in early embryonic development in goats by regulating expression of EGA-associated genes.

Nuclear-localized eukaryotic translation initiation factor 1A is involved in mouse preimplantation embryo development

Preimplantation embryo development is characterized by drastic nuclear reprogramming and dynamic stage-specific gene expression. Key regulators of this earliest developmental stage have not been revealed. In the present study, a "non-classical" nuclear-localization pattern of eIF1A was observed during early developmental stages of mouse preimplantation embryo before late-morula. In particular, eIF1A is most highly expressed in the nuclear of 2-cell embryo. Knockdown eIF1A by siRNA microinjection affected the development of mouse preimplantation embryo, resulted in decreased blastocyst formation rate. CDX2 protein expression level significantly down-regulated after eIF1A knockdown in morula stage. In addition, the mRNA expression level of Hsp70.1 was also decreased in 2-cell embryo. The results indicate an indispensable role of eIF1A in mouse preimplantation embryos.

LC3-Dependent Autophagy in Pig 2-Cell Cloned Embryos Could Influence the Degradation of Maternal mRNA and the Regulation of Epigenetic Modification

In this study, the distribution as well as the effect of autophagy on reprogramming in pig cloned embryos were observed immediately after somatic cell nuclear transfer. Results showed that the LC3 was at the highest level in cloned embryos at 2-cell stage, and it decreased with the development from 2-cell stage to blastocyst. Different to cloned embryos, the intensity of LC3 in parthenogenetic activation (PA) embryos was at the highest level at 4-cell stage. A markedly higher level of Bmp15, H1foo, and Dppa3 was shown in cloned embryos at 2-cell stage (p < 0.05 or p < 0.01), but a significantly lower level of LC3, Sox2, and eIF1A was observed at 4-cell stage (p < 0.05), compared with PA embryos. When the efficient interfering by the LC3 siRNA was performed on the cloned embryos (p < 0.01), not only the mRNA level of maternal Cyclin B, Bmp15, Gdf9, c-mos, H1foo, and Dppa3 was increased significantly (p < 0.05), but also the expression of Dnmt1 and Dnmt3b was obviously upregulated (p < 0.05). Although the expression of Sox2 and Oct4 is not changed, the expression of Stat3 decreased significantly (p < 0.05). Furthermore with the treatment of 200 nM rapamycin, the expression of eIF1A and Stat3 was significantly increased at 4-cell stage. In conclusion, the LC3-dependent autophagy mainly occurred in cloned embryos at 2-cell stage, but at 4-cell stage in PA embryos. In addition, the modulation of autophagy could affect genome activation by influencing the degradation of maternal mRNA and regulating the expression of DNA methyltransferase.

Methods of RNA preparation affect mRNA abundance quantification of reference genes in pig maturing oocytes

To ensure accurate normalization and quantification of target RNA transcripts using reverse transcription quantitative polymerase chain reaction (RT-qPCR), most studies focus on the identification of stably expressed gene(s) as internal reference. However, RNA preparation methods could also be an important factor, especially for test samples of limited quantity (e.g. oocytes). In this study, we aimed to select appropriate reference gene(s), and evaluate the effect of RNA preparation methods on gene expression quantification in porcine oocytes and cumulus cells during in vitro maturation. Expression profiles of seven genes (GAPDH, 18S, YWHAG, BACT, RPL4, HPRT1 and PPIA) were examined, on RNA samples extracted from cumulus cells (RNeasy Kit) and oocytes (RNeasy Kit and Lysis Kit) during in vitro maturation, respectively. Interestingly, different RNA preparation methods were found to potentially affect the quantification of reference gene expression in pig oocytes cultured in vitro. After geNorm analyses, the most suitable genes for normalization were identified, GAPDH/18S for cumulus cells and YWHAG/BACT for oocytes, respectively. Thus, our results provide useful data and information on the selection of better reference genes and RNA preparation method for related functional studies.

Expression of eukaryotic elongation initiation factor 1A differentially marks zygotic genome activation in biparental and parthenogenetic porcine embryos and correlates with in vitro developmental potential

Zygotic genome activation (ZGA) is a major event during cleavage development. In vitro manipulation of mammalian embryos (including embryo culture) can result in developmental arrest around the time of ZGA. Eukaryotic elongation initiation factor 1A (eIF1A) has been used as a marker for ZGA in some mammalian species. We hypothesised expression of eIF1A can be used to assess ZGA in the pig; we also hypothesised that the expression profile of eIF1A can be used to assess developmental potential in vitro. The aims of the present study were to determine the expression pattern of eIF1A during porcine cleavage development and to assess its expression levels in embryos of different quality. We used a real-time reverse transcription-polymerase chain reaction assay to quantify eIF1A transcripts at different time points during cleavage development in porcine embryos produced by parthenogenetic activation (PA) and in vitro fertilisation (IVF). We found that eIF1A is activated at the two-cell stage in IVF embryos and at the four-cell stage in PA embryos. We showed that the increase in transcript levels observed in parthenogenetic embryos is dependent on de novo transcription. We found altered levels of eIF1A transcripts in parthenogenetic embryos that presented as either two- or eight-cell embryos 48 h after activation compared with four-cell embryos at the same time point. Our work supports the hypothesis that eIF1A is a marker of porcine ZGA and its expression profile can be used to assess embryo quality.

Maternally derived transcripts: identification and characterisation during oocyte maturation and early cleavage

The identification and characterisation of differentially regulated genes in oocytes and early embryos are required to understand the mechanisms involved in maturation, fertilisation, early cleavage and even long-term development. Several methods, including reverse transcription-polymerase chain reaction-based suppression subtractive hybridisation, differential display and cDNA microarray, have been applied to identify maternally derived genes in mammalian oocytes. However, conventional gene-knockout experiments to determine specific gene functions are labour intensive and inefficient. Recent developments include the use of RNA interference techniques to establish specific gene functions in mammalian oocytes and early embryos. Regulation of the poly(A) tail length is a major factor in controlling the activities of maternal transcripts in mammals. Further studies are required to clarify the mechanisms by which expression levels of maternally derived transcripts are regulated. In the present review, we focus on the identification and functions of the differentially expressed transcripts during oocyte maturation, fertilisation and early cleavage.

Changing genetic world of IVF, stem cells and PGD. B. Polarities and gene expression in differentiating embryo cells and stem cells

Novel genetic techniques in the later twentieth century led to new analytical methods for assessing the growth of embryos and stem cells and improve preimplantation diagnosis. Increasing attention to the nature of polarities in mouse and human embryos revealed the existence of an animal-vegetal axis in human oocytes and embryos. Combinations of meridional and transverse cleavage divisions, the latter due to spindle rotation, determined the unequal division of ooplasm to embryonic blastomeres. Blastomeres with differing functions were accordingly formed in 4-cell embryos, including founders of inner cell mass and trophectoderm. New forms of gene analysis led to the polymerase chain reaction, while fluorescence in-situ hybridization revealed astonishingly high degrees of heteroploidy in human embryos. Developmental genetics gained immense analytical power as cDNA libraries, microarrays, transcriptomes RNAi and other methods clarified the roles of hundreds of genes in pre- and early post-implantation embryos and stem cells.

Genetics of polarity in mammalian embryos

This brief review is devoted to the genetic control of polarity and embryonic axes in preimplantation mammalian embryos. Discussion is related to their formation, the considerable variations in gene activity in these early phases of development, and the influence of timers over polarities and related aspects of development. Modern genetic analyses assess vast numbers of genes in outline, and the actions of individual genes in detail. These factors operate within a mixture of inherited maternal controls, gene silencing, bouts of transcription and the actions of mini RNA in controlling gene expression. Within this context, maternal factors regulate the planes of early cleavage divisions and unevenly distribute animal and vegetal characteristics to successive blastomeres by the 4-cell stage. This varied inheritance confers varying combinations of animal and vegetal cytoplasm to single blastomeres in many human 4-cell embryos. The blastomere inheriting animal cytoplasm only may be the trophectodermal stem cell, that with vegetal cytoplasm may be the germline precursor, and the two with full polarity may produce inner cell mass. Some implications of these findings are considered.

Optimization of real time RT-PCR methods for the analysis of gene expression in mouse eggs and preimplantation embryos

This study was carried out to optimize conditions for using real time RT-PCR as an efficient and precise quantitative method for estimating the transcript levels of genes expressed in samples containing miniscule amounts of RNA, such as single mammalian oocytes and embryos. First, using mouse eggs and blastocysts, we tested three kinds of RNA isolation or collection methods: TRIZOL reagent, oligo-dT conjugated beads, or three freeze/thaw cycles with the reverse transcription buffer. There were no significant differences among three groups in mRNA quantity as assayed by real time RT-PCR analysis. Second, we compared the efficacy of real time analysis between TaqMan fluorescent probes and the SYBR-green dye system. The two systems presented similar real time RT-PCR profiles for the 16s ribosomal protein gene from oocytes to blastocysts. Third, RNA from mouse embryos at defined stages of preimplantation development were isolated and the levels of transcripts encoded by several housekeeping genes (GAPDH, beta-actin, ribosomal protein L7, 16s ribosomal protein, histone H2A.Z) were quantitatively analyzed by real time RT-PCR. The histone H2A.Z and 16s ribosomal protein slightly increased from the egg to blastocyst stages by approximately 10- and 30-fold, respectively. However, other transcripts increased more than 300-fold as a function of developmental stage from eggs to blastocysts. Our results suggest that the simple freezing/thawing method for RNA collection, the economic SYBR-green dye system, and histone H2A.Z gene as an internal control should be useful for the real time RT-PCR analysis of single mouse eggs and preimplantation embryos.

Predicting embryo quality: mRNA expression and the preimplantation embryo

To overcome the low implantation rate (10-20%) following IVF in humans, more than two embryos are commonly replaced, potentially leading to high order multiple pregnancies with associated significantly elevated risks. Selecting the most viable embryos and transferring fewer of them could reduce this risk. Prolonged culture of embryos in vitro to the blastocyst stage may expose the embryo to hazards not normally encountered in the female reproductive tract. Recent studies comparing bovine oocyte maturation, fertilization and embryo culture in vivo and in vitro have demonstrated that the origin of the oocyte is the main factor affecting blastocyst yield, while the post-fertilization culture environment is crucial in determining blastocyst quality, measured in terms of cryotolerance and relative transcript abundance, irrespective of the origin of the oocyte. Production of embryos in vitro, particularly when using an extended period of in-vitro culture may predispose the embryo to phenomena such as 'large offspring syndrome', which is probably linked to altered gene expression, particularly of imprinted genes. Post-fertilization culture environment clearly has a profound effect on the relative abundance of gene transcripts within the embryo. Culture under sub-optimal conditions for even one day can lead to perturbations in the pattern of expression.