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6-Bromoindirubin-3′-oxime (BIO), which is one of the glycogen synthase kinase 3 inhibitors and a key regulator of numerous signaling pathways, was reported to be capable of maintaining the pluripotency of human and mouse embryonic stem cells. Presently, it is unknown whether BIO can influence the derivation of porcine embryonic germ (EG) cells. In this study, porcine primordial germ cells (PGCs) were isolated from gonads of 24- and 28-day embryos, and were then treated with BIO either individually or in combination with other cytokines (stem cell factor (SCF), leukemia inhibitory factor (LIF), and fibroblast growth factor (FGF); abbreviated as ‘3F’), and the effects of the treatment on the proliferation ability of porcine PGCs at early stage were examined using 5-bromo-2-deoxyuridine (Brdu) immunostaining assay. After continuous culture, the effects on the efficiency of porcine undifferentiated EG cells in the third passage and differentiated EG cells from embryoid bodies were examined as well. The results obtained through the observation of the Brdu-labeled PGCs indicated that BIO in combination with 3F resulted in a significant increase in the mitosis index, and also indicated that the BIO in combination with 3F had a higher efficiency in promoting the formation of porcine EG colony derived from porcine day 24 PGCs than BIO used either individually or in combination with LIF. In addition, BIO in combination with 3F exhibited the apparent anti-differentiation activity by reversing the differentiated EG cells to the undifferentiated status. Our results demonstrate that BIO in combination with SCF, LIF, and FGF could significantly contribute to the establishment of a porcine EG cell colony and maintain the undifferentiated status.

TET1 is implicated in maintaining the pluripotency of embryonic stem cells. However, its precise effects on induced pluripotent stem cells (iPSCs), and particularly on porcine iPSCs (piPSCs), are not well defined. To investigate the role of TET1 in the pluripotency and differentiation of piPSCs, piPSCs were induced from porcine embryonic fibroblasts by overexpression of POU5F1 (OCT4), SOX2, KLF4, and MYC (C-MYC). siRNAs targeting to TET1 were used to transiently knockdown the expression of TET1 in piPSCs. Morphological abnormalities and loss of the undifferentiated state of piPSCs were observed in the piPSCs after the downregulation of TET1. The effects of TET1 knockdown on the expression of key stem cell factors and differentiation markers were analyzed to gain insights into the molecular mechanisms underlying the phenomenon. The results revealed that knockdown of TET1 resulted in the downregulated expression of pluripotency-related genes, such as LEFTY2, KLF2, and SOX2, and the upregulated expression of differentiation-related genes including PITX2, HAND1, GATA6, and LEF1. However, POU5F1, M YC, KLF4, and NANOG were actually not downregulated. Further analysis showed that the methylation levels of the promoters for POU5F1 and M YC increased significantly after TET1 downregulation, whereas there were no obvious changes in the promoters of SOX2, KLF4, and NANOG. The methylation of the whole genome increased, while hydroxymethylation slightly declined. Taken together, these results suggest that TET1 may play important roles in the self-renewal of piPSCs and the maintenance of their characteristics by regulating the expression of genes and the DNA methylation.

DNA methylation and histone modification play important roles in the development of mammalian embryos. Cytochalasin B (CB) is an actin polymerization inhibitor that can significantly affect cell activity and is often used in studies concerning cytology. In recent years, CB is also commonly being used in in vitro experiments on mammalian embryos, but few studies have addressed the effect of CB on the epigenetic modification of embryonic development, and the mechanism underlying this process is also unknown. This study was conducted to investigate the effects of CB on DNA methylation and histone modification in the development of parthenogenetically activated porcine embryos. Treatment with 5 μg/mL CB for 4 h significantly increased the cleavage rate, blastocyst rate and total cell number of blastocysts. However, the percentage of apoptotic cells and the expression levels of the apoptosis-related genes BCL-XL, BAX and CASP3 were significantly decreased. Treatment with CB significantly decreased the expression levels of DNMT1, DNMT3a, DNMT3b, HAT1 and HDAC1 at the pronuclear stage and promoted the conversion of 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC). After CB treatment, the level of AcH3K9 was upregulated and the level of H3K9me3 was downregulated. When combined with Scriptaid and 5-Aza-Cdr, CB further improved the embryonic development competence and decreased the expression of BCL-XL, BAX and CASP3. In conclusion, these results suggest that CB could improve embryonic development and the quality of the blastocyst by improving the epigenetic modification during the development of parthenogenetically activated embryos.

The Wilms' tumour 1 (WT1) gene originally identified as a tumour suppressor associated with WTs encodes a zinc finger-containing transcription factor that is expressed in multiple tissues and is an important regulator of cellular and organ growth, proliferation, development, migration and survival. However, there is a deficiency of data regarding the expression and function of WT1 during oocyte maturation and preimplantation embryonic development. Herein, we sought to define the expression characteristics and functions of WT1 during oocyte maturation and preimplantation embryonic development in pigs. We show that WT1 is expressed in porcine oocytes and at all preimplantation stages in embryos generated by ICSI. We then evaluated the effects of down-regulating WT1 expression at germinal vesicle and early ICSI stages using a recombinant plasmid (pGLV3-WT1-shRNA). Down-regulation of WT1 did not affect oocyte maturation but significantly decreased preimplantation embryonic development and increased apoptosis in blastocysts. These results indicate that WT1 plays important roles in the development of porcine preimplantation embryos.

Sertoli cells are indispensable for normal spermatogenesis, and increasing evidence has shown that miRNAs participate in the regulation of Sertoli cell growth. However, the functions and regulatory mechanisms of miRNAs in Sertoli cells of domestic animals have not been fully investigated. In the present study, we mainly investigated the regulatory roles of miR-499 in immature porcine Sertoli cells. The results showed that miR-499 was mainly located in the basement section of seminiferous tubules of prepubertal porcine testicular tissue. Overexpression of miR-499 promoted cell proliferation and inhibited apoptosis, whereas miR-499 inhibition resulted in the opposite effect. The PTEN gene was directly targeted by miR-499, and the expression of mRNA and protein was also negatively regulated by miR-499 in immature porcine Sertoli cells. siRNA-induced PTEN knockdown resulted in a similar effect as an overexpression of miR-499 and abolished the effects of miR-499 inhibition on immature porcine Sertoli cells. Moreover, both miR-499 overexpression and the PTEN knockdown activated the PI3K/AKT signaling pathway, whereas inhibition of the PI3K/AKT signaling pathway caused immature porcine Sertoli cell apoptosis and inhibited cell proliferation. Overall, miR-499 promotes proliferation and inhibits apoptosis in immature porcine Sertoli cells through the PI3K/AKT pathway by targeting the PTEN gene. This study provides novel insights into the effects of miR-499 in spermatogenesis through the regulation of immature Sertoli cell proliferation and apoptosis.

Distant hybridization refers to the cross between two different species or higher-ranking taxa. It is very significant if the new lineages with genetic variation, fertile ability, and improved characteristics can be established through distant hybridization. However, reproductive barriers are key limitations that must be overcome to establish fertile lineages derived from distant hybridization. In the present review, we discussed how distant hybridization is an important way to form new species by overcoming reproductive barriers and summarized effective measures to overcome reproductive barriers in order to create fertile lineages of fish distant hybridization. In addition, we described the utilization of the fish lineages derived from distant hybridization. Finally, we discussed the relationship between distant hybridization and Mendel’s laws, which generally apply to the inbred hybridization. We aim to provide a comprehensive reference for the establishment of fertile fish lineages by overcoming reproductive barriers and to emphasize the significance of fish distant hybridization in the fields of evolutionary biology, reproductive biology, and genetic breeding.

Somatic cell nuclear transfer (SCNT) has been successfully used for cloning in a variety of mammalian species. However, SCNT reprogramming efficiency is relatively low, in part, due to incomplete DNA methylation reprogramming of donor cell nuclei. We previously showed that ten-eleven translocation 3 (TET3) is responsible for active DNA demethylation during preimplantation embryonic development in bovines. In this study, we constructed TET3-overexpressing cell lines in vitro and observed that the use of these fibroblasts as donor cells increased the blastocyst rate by approximately 18 percentage points compared to SCNT. The overexpression of TET3 in bovine SCNT embryos caused a decrease in the global DNA methylation level of the pluripotency genes Nanog and Oct-4, ultimately resulting in an increase in the transcriptional activity of these pluripotency genes. Moreover, the quality of bovine TET3-NT embryos at the blastocyst stage was significantly improved, and bovine TET3-NT blastocysts possessed more total number of cells and fewer apoptotic cells than the SCNT blastocysts, similar to in vitro fertilization (IVF) embryos. Nevertheless, DNA methylation of the imprinting control region (ICR) for the imprinted genes H19-IGF2 in SCNT embryos remained unaffected by TET3 overexpression, maintaining parent-specific activity for further development. Thus, the results of our study provide a promising approach to rectify incomplete epigenetic reprogramming and achieve higher cloning efficiency.