Combined Chaetocin/Trichostatin A Treatment Improves the Epigenetic Modification and Developmental Competence of Porcine Somatic Cell Nuclear Transfer Embryos

Developmental defects in somatic cell nuclear transfer (SCNT) embryos are principally attributable to incomplete epigenetic reprogramming. Small-molecule inhibitors such as histone methyltransferase inhibitors (HMTi) and histone deacetylase inhibitors (HDACi) have been used to improve reprogramming efficiency of SCNT embryos. However, their possible synergistic effect on epigenetic reprogramming has not been studied. In this study, we explored whether combined treatment with an HMTi (chaetocin) and an HDACi (trichostatin A; TSA) synergistically enhanced epigenetic reprogramming and the developmental competence of porcine SCNT embryos. Chaetocin, TSA, and the combination significantly increased the cleavage and blastocyst formation rate, hatching/hatched blastocyst rate, and cell numbers and survival rate compared to control embryos. In particular, the combined treatment improved the rate of development to blastocysts more so than chaetocin or TSA alone. TSA and combined chaetocin/TSA significantly reduced the H3K9me3 levels and increased the H3K9ac levels in SCNT embryos, although chaetocin alone significantly reduced only the H3K9me3 levels. Moreover, these inhibitors also decreased global DNA methylation in SCNT embryos. In addition, the expression of zygotic genome activation- and imprinting-related genes was increased by chaetocin or TSA, and more so by the combination, to levels similar to those of in vitro-fertilized embryos. These results suggest that combined chaetocin/TSA have synergistic effects on improving the developmental competences by regulating epigenetic reprogramming and correcting developmental potential-related gene expression in porcine SCNT embryos. Therefore, these strategies may contribute to the generation of transgenic pigs for biomedical research.

Histone Demethylase KDM4D Could Improve the Developmental Competence of Buffalo (Bubalus Bubalis) Somatic Cell Nuclear Transfer (SCNT) Embryos

Somatic cell nuclear transfer (SCNT) holds vast potential in agriculture. However, its applications are still limited by its low efficiency. Histone 3 lysine 9 trimethylation (H3K9me3) was identified as an epigenetic barrier for this. Histone demethylase KDM4D could regulate the level of H3K9me3. However, its effects on buffalo SCNT embryos are still unclear. Thus, we performed this study to explore the effects and underlying mechanism of KDM4D on buffalo SCNT embryos. The results revealed that compared with the IVF embryos, the expression level of KDM4D in SCNT embryos was significantly lower at 8- and 16-cell stage, while the level of H3K9me3 in SCNT embryos was significantly higher at 2-cell, 8-cell, and blastocyst stage. Microinjection of KDM4D mRNA could promote the developmental ability of buffalo SCNT embryos. Furthermore, the expression level of ZGA-related genes such as ZSCAN5B, SNAI1, eIF-3a, and TRC at the 8-cell stage was significantly increased. Meanwhile, the pluripotency-related genes like POU5F1, SOX2, and NANOG were also significantly promoted at the blastocyst stage. The results were reversed after KDM4D was inhibited. Altogether, these results revealed that KDM4D could correct the H3K9me3 level, increase the expression level of ZGA and pluripotency-related genes, and finally, promote the developmental competence of buffalo SCNT embryos.

Prediabetes Induced by a Single Autoimmune B Cell Clone

While B cells play a significant role in the onset of type-1 diabetes (T1D), little is know about their role in those early stages. Thus, to gain new insights into the role of B cells in T1D, we converted a physiological early pancreas-infiltrating B cell into a novel BCR mouse model using Somatic Cell Nuclear Transfer (SCNT). Strikingly, SCNT-derived B1411 model displayed neither developmental block nor anergy. Instead, B1411 underwent spontaneous germinal center reactions. Without T cell help, B1411-Rag1^−/− was capable of forming peri-/intra-pancreatic lymph nodes, and undergoing class-switching. RNA-Seq analysis identified 93 differentially expressed genes in B1411 compared to WT B cells, including Irf7, Usp18, and Mda5 that had been linked to a potential viral etiology of T1D. We also found various members of the oligoadenylate synthase (OAS) family to be enriched in B1411, such as Oas1, which had recently also been linked to T1D. Strikingly, when challenged with glucose B1411-Rag1^−/− mice displayed impaired glucose tolerance.

Effects of resveratrol on in vitro maturation of porcine oocytes and subsequent early embryonic development following somatic cell nuclear transfer

As a natural plant-derived antitoxin, resveratrol possesses several pharmacological activities. This study aimed to evaluate the effects of resveratrol addition on nuclear maturation, oocyte quality during in vitro maturation (IVM) of porcine oocytes and subsequent early embryonic development following somatic cell nuclear transfer (SCNT). Our experiments showed that the treatment of porcine oocytes with 5 µM resveratrol during IVM resulted in the highest rate of the first polar body extrusion. Treatment of oocytes with resveratrol had no influence on cytoskeletal dynamics, whereas it significantly increased glucose uptake ability compared to the control oocytes. Oocytes matured with 5 μM resveratrol displayed significantly lower intracellular reactive oxygen species (ROS) levels and higher relative mRNA expression levels of the genes encoding such antioxidant enzymes as catalase (CAT) and superoxide dismutase 1 (SOD1). In addition, resveratrol also prevented onset and progression of programmed cell death in porcine oocytes, which was confirmed by significant upregulation of the anti-apoptotic B-cell lymphoma 2 (BCL-2) gene and significant downregulation of the pro-apoptotic BCL2-associated X (BAX) gene. Furthermore, the blastocyst rates and the blastocyst cell numbers in cloned embryos derived from the oocytes that had matured in the presence of 5 μM resveratrol were significantly increased. In conclusion, supplementation of IVM medium with 5 μM resveratrol improves the quality of porcine oocytes by protecting them from oxidative damage and apoptosis, which leads to the production of meiotically matured oocytes exhibiting enhanced developmental potential following SCNT.

Hairless-knockout piglets generated using the clustered regularly interspaced short palindromic repeat/CRISPR-associated-9 exhibit abnormalities in the skin and thymus

The nuclear receptor corepressor Hairless (HR) interacts with nuclear receptors and controls expression of specific target genes involved in hair morphogenesis and hair follicle cycling. Patients with HR gene mutations exhibit atrichia, and in rare cases, immunodeficiency. Pigs with HR gene mutations may provide a useful model for developing therapeutic strategies because pigs are highly similar to humans in terms of anatomy, genetics, and physiology. The present study aimed to knockout the HR gene in pigs using the clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated-9 (Cas9) system and to investigate the molecular and structural alterations in the skin and thymus. We introduced a biallelic mutation into the HR gene in porcine fetal fibroblasts and generated nine piglets via somatic cell nuclear transfer. These piglets exhibited a lack of hair on the eyelids, abnormalities in the thymus and peripheral blood, and altered expression of several signaling factors regulated by HR. Our results indicate that introduction of the biallelic mutation successfully knocked out the HR gene, resulting in several molecular and structural changes in the skin and thymus. These pigs will provide a useful model for studying human hair disorders associated with HR gene mutations and the underlying molecular mechanisms.

The Histone Deacetylase Inhibitor, CI994, Improves Nuclear Reprogramming and In Vitro Developmental Potential of Cloned Pig Embryos

Epigenetic reprogramming and somatic cell nuclear transfer (SCNT) cloning efficiency were recently enhanced using histone deacetylase inhibitors (HDACis). In this study, we investigated the time effect of CI994, an HDACi, on the blastocyst formation rate, acetylation levels of H3K9 and H4K12, DNA methylation levels of anti-5-methylcytosine (5mC), and some mRNA expression of pluripotency-related genes in pig SCNT embryos. Treatment with 10 μM CI994 for 24 hours significantly improved the blastocyst formation rate of SCNT embryos in comparison with the untreated group (p < 0.05). Moreover, average fluorescence intensities of H3K9 and H4K12 in CI994-treated embryos were remarkably increased at the pseudo-pronuclear stage, but not at the blastocyst stage. The intensity of POU5F1 was higher in CI994-treated blastocysts than in control blastocysts, whereas that of 5mC did not differ between the two groups. The percentage of apoptotic cells in blastocysts was significantly higher in the untreated group than in the CI994-treated group. mRNA levels of POU5F1 and SOX2 were significantly increased in the CI994-treated group. These observations suggest that optimum exposure (10 μM for 24 hours) to CI994 after activation elevates the level of histone acetylation and subsequently improves the in vitro development of pig SCNT embryos.

Overexpression of MicroRNA-29b Decreases Expression of DNA Methyltransferases and Improves Quality of the Blastocysts Derived from Somatic Cell Nuclear Transfer in Cattle

MicroRNA (miR)-29b plays a crucial role during somatic cell reprogramming. The aim of the current study was to explore the effects of miR-29b on the developmental competence of bovine somatic cell nuclear transfer (SCNT) embryos, as well as the underlying mechanisms of action. The expression level of miR-29b was lower in bovine SCNT embryos at the pronuclear, 8-cell, and blastocyst stages compared with in vitro fertilized embryos. In addition, miR-29b regulates the expression of DNA methyltransferases (Dnmt3a/3b and Dnmt1) in bovine SCNT embryos. We further investigated SCNT embryo developmental competence and found that miR-29b overexpression during bovine SCNT embryonic development does not improve developmental potency and downregulation inhibits developmental potency. Nevertheless, the quality of bovine SCNT embryos at the blastocyst stage improved significantly. The expression of pluripotency factors and cellular proliferation were significantly higher in blastocysts from the miR-29b overexpression group than the control and downregulation groups. In addition, outgrowth potential in blastocysts after miR-29b overexpression was also significantly greater in the miR-29b overexpression group than in the control and downregulation groups. Taken together, these results demonstrated that miR-29b plays an important role in bovine SCNT embryo development.

Generation of DKK1 transgenic Tibet minipigs by somatic cell nuclear transfer (SCNT)

Hairless mice have been widely applied in skin-related researches, while hairless pigs will be a useful model for skin-related study and other biomedical researches. Dickkopf-related protein 1 (DKK1) is inhibitor of Wnt signaling pathway. Transgenic mice expressing DKK1 transgene under control of a human keratin 14 (K14) promoter display hairless phenotype, which encouraged us to generate transgenic minipigs expressing pig DKK1 transgene under control of K14 promoter and finally achieve hairless minipigs. To generate transgenic cloned pigs, we constructed the lentiviral expression vector pERKDZG which contains two independent expression cassettes, the transcription of Tibet minipig DKK1 and EGFP genes are driven by K14 promoter, while mRFP is regulated under the control of Ef-1α promoter. Prior to generating the transgenic pig, the functionality of pERKDZG construct was verified by fluorescence assay and via checking pDKK1 expression. Subsequently, lentiviruses harboring ERKDZG transgene infected porcine embryonic fibroblasts (PEFs), followed by sorting RFP-positive PEFs by flow cytometry to obtain the purified PEFs carrying ERKDZG, designated DKK1-PEFs as donor cells used for somatic cell nuclear transfer (SCNT). Finally, we obtained 3 DKK1 transgenic cloned pigs with skin-specific expression of pDKK1 and EGFP transgenes, but unfortunately, DKK1 transgenic cloned pigs don't display hairless phenotype as expected. Taken together, we achieve DKK1 transgenic cloned pigs with skin-specific expression of pDKK1 transgene which provide a pig model for exploring DKK1 gene functions in pigs.

Coexpression analysis identifies nuclear reprogramming barriers of somatic cell nuclear transfer embryos

The success of cloned animal "Dolly Sheep" demonstrated the somatic cell nuclear transfer (SCNT) technique holds huge potentials for mammalian asexual reproduction. However, the extremely poor development of SCNT embryos indicates their molecular mechanism remain largely unexplored. Deciphering the spatiotemporal patterns of gene expression in SCNT embryos is a crucial step toward understanding the mechanisms associated with nuclear reprogramming. In this study, a valuable transcriptome recourse of SCNT embryos was firstly established, which derived from different inter-/intra donor cells. The gene co-expression analysis identified 26 cell-specific modules, and a series of regulatory pathways related to reprogramming barriers were further enriched. Compared to the intra-SCNT embryos, the inter-SCNT embryos underwent only complete partially reprogramming. As master genome trigger genes, the transcripts related to TFIID subunit, RNA polymerase and mediators were incomplete activated in inter-SCNT embryos. The inter-SCNT embryos only wasted the stored maternal mRNA of master regulators, but failed to activate their self-sustained pathway of RNA polymerases. The KDM family of epigenetic regulator also seriously delayed in inter-SCNT embryo reprogramming process. Our study provided new insight into understanding of the mechanisms of nuclear reprogramming.

Reprogramming of fibroblast nuclei in cloned bovine embryos involves major structural remodeling with both striking similarities and differences to nuclear phenotypes of in vitro fertilized embryos

Nuclear landscapes were studied during preimplantation development of bovine embryos, generated either by in vitro fertilization (IVF), or generated as cloned embryos by somatic cell nuclear transfer (SCNT) of bovine fetal fibroblasts, using 3-dimensional confocal laser scanning microscopy (3D-CLSM) and structured illumination microscopy (3D-SIM). Nuclear landscapes of IVF and SCNT embryonic nuclei were compared with each other and with fibroblast nuclei. We demonstrate that reprogramming of fibroblast nuclei in cloned embryos requires changes of their landscapes similar to nuclei of IVF embryos. On the way toward the 8-cell stage, where major genome activation occurs, a major lacuna, enriched with splicing factors, was formed in the nuclear interior and chromosome territories (CTs) were shifted toward the nuclear periphery. During further development the major lacuna disappeared and CTs were redistributed throughout the nuclear interior forming a contiguous higher order chromatin network. At all stages of development CTs of IVF and SCNT embryonic nuclei were built up from chromatin domain clusters (CDCs) pervaded by interchromatin compartment (IC) channels. Quantitative analyses revealed a highly significant enrichment of RNA polymerase II and H3K4me3, a marker for transcriptionally competent chromatin, at the periphery of CDCs. In contrast, H3K9me3, a marker for silent chromatin, was enriched in the more compacted interior of CDCs. Despite these striking similarities, we also detected major differences between nuclear landscapes of IVF and cloned embryos. Possible implications of these differences for the developmental potential of cloned animals remain to be investigated. We present a model, which integrates generally applicable structural and functional features of the nuclear landscape.