Immune rebalancing at the maternal-fetal interface of maternal SARS-CoV-2 infection during early pregnancy.

The current coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus (SARS-CoV-2) remains a threat to pregnant women. However, the impact of early pregnancy SARS-CoV-2 infection on the maternal-fetal interface remains poorly understood. Here, we present a comprehensive analysis of single-cell transcriptomics and metabolomics in placental samples infected with SARS-CoV-2 during early pregnancy. Compared to control placentas, SARS-CoV-2 infection elicited immune responses at the maternal-fetal interface and induced metabolic alterations in amino acid and phospholipid profiles during the initial weeks post-infection. However, subsequent immune cell activation and heightened immune tolerance in trophoblast cells established a novel dynamic equilibrium that mitigated the impact on the maternal-fetal interface. Notably, the immune response and metabolic alterations at the maternal-fetal interface exhibited a gradual decline during the second trimester. Our study underscores the adaptive immune tolerance mechanisms and establishment of immunological balance during the first two trimesters following maternal SARS-CoV-2 infection.

Pterostilbene: a potential therapeutic agent for fibrotic diseases.

Fibrosis is a prevailing pathology in chronic diseases and accounts for 45% of deaths in developed countries. This condition is primarily identified by the transformation of fibroblasts into myofibroblasts and the overproduction of extracellular matrix (ECM) by myofibroblasts. Pterostilbene (PTS) is a natural analogue of resveratrol and is most commonly found in blueberries. Research has shown that PTS exerts a wide range of pharmacological effects, such as antioxidant, anti-inflammatory, and anticancer effects. As a result, PTS has the potential to prevent and cure numerous diseases. Emerging evidence has indicated that PTS can alleviate myocardial fibrosis, renal fibrosis, pulmonary fibrosis, hepatic fibrosis, and colon fibrosis via the inhibition of inflammation, oxidative stress, and fibrogenesis effects in vivo and in vitro, and the potential mechanisms are linked to various pathways, including transforming growth factor-ß1 (TGF-ß1)/small mother against decapentaplegic proteins (Smads) signalling, the reactive oxygen species (ROS)-driven Pitx2c/mir-15b pathway, nuclear factor kappa B (NF-κB) signalling, Kelch-like epichlorohydrin-associated protein-1 (Keap-1)/NF-E2-related factor-2 (Nrf2) cascade, the NLR family pyridine structure domain 3 (NLRP3) pathway, the Janus kinase-2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway, and the Src/STAT3 pathway. In this review, we comprehensively summarize the antifibrotic effects of PTS both in vivo and in vitro and the pharmacological mechanisms, pharmacokinetics, and toxicology of PTS and provide insights into and strategies for exploring promising agents for the treatment of fibrosis.

Maternal Ezh1/2 deficiency impairs the function of mitochondria in mouse oocytes and early embryos.

Maternal histone methyltransferase is critical for epigenetic regulation and development of mammalian embryos by regulating histone and DNA modifications. Here, we reported a novel mechanism by revealing the critical effects of maternal Ezh1/2 deletion on mitochondria in MII oocytes and early embryos in mice. We found that Ezh1/2 knockout in mouse MII oocytes impaired the structure of mitochondria and decreased its number, but membrane potential and respiratory function of mitochondrion were increased. The similar effects of Ezh1/2 deletion have been observed in 2-cell and morula embryos, indicating that the effects of maternal Ezh1/2 deficiency on mitochondrion extend to early embryos. However, the loss of maternal Ezh1/2 resulted in a severe defect of morula: the number, membrane potential, respiratory function, and ATP production of mitochondrion dropped significantly. Content of reactive oxygen species was raised in both MII oocytes and early embryos, suggesting maternal Ezh1/2 knockout induced oxidative stress. In addition, maternal Ezh1/2 ablation interfered the autophagy in morula and blastocyst embryos. Finally, maternal Ezh1/2 deletion led to cell apoptosis in blastocyst embryos in mice. By analyzing the gene expression profile, we revealed that maternal Ezh1/2 knockout affected the expression of mitochondrial related genes in MII oocytes and early embryos. The chromatin immunoprecipitation-polymerase chain reaction assay demonstrated that Ezh1/2 directly regulated the expression of genes Fxyd6, Adpgk, Aurkb, Zfp521, Ehd3, Sgms2, Pygl, Slc1a1, and Chst12 by H3K27me3 modification. In conclusion, our study revealed the critical effect of maternal Ezh1/2 on the structure and function of mitochondria in oocytes and early embryos, and suggested a novel mechanism underlying maternal epigenetic regulation on early embryonic development through the modulation of mitochondrial status.

Comprehensive transcriptional atlas of human adenomyosis deciphered by the integration of single-cell RNA-sequencing and spatial transcriptomics.

Adenomyosis is a poorly understood gynecological disorder lacking effective treatments. Controversy persists regarding "invagination" and "metaplasia" theories. The endometrial-myometrial junction (EMJ) connects the endometrium and myometrium and is important for diagnosing and classifying adenomyosis, but its in-depth study is just beginning. Using single-cell RNA sequencing and spatial profiling, we mapped transcriptional alterations across eutopic endometrium, lesions, and EMJ. Within lesions, we identified unique epithelial (LGR5+) and invasive stromal (PKIB+) subpopulations, along with WFDC1+ progenitor cells, supporting a complex interplay between "invagination" and "metaplasia" theories of pathogenesis. Further, we observed endothelial cell heterogeneity and abnormal angiogenic signaling involving vascular endothelial growth factor and angiopoietin pathways. Cell-cell communication differed markedly between ectopic and eutopic endometrium, with aberrant signaling in lesions involving pleiotrophin, TWEAK, and WNT cascades. This study reveals unique stem cell-like and invasive cell subpopulations within adenomyosis lesions identified, dysfunctional signaling, and EMJ abnormalities critical to developing precise diagnostic and therapeutic strategies.

Inhibition of Wnt activity improves peri-implantation development of somatic cell nuclear transfer embryos.

Somatic cell nuclear transfer (SCNT) can reprogram differentiated somatic cells into totipotency. Although pre-implantation development of SCNT embryos has greatly improved, most SCNT blastocysts are still arrested at the peri-implantation stage, and the underlying mechanism remains elusive. Here, we develop a 3D in vitro culture system for SCNT peri-implantation embryos and discover that persistent Wnt signals block the naïve-to-primed pluripotency transition of epiblasts with aberrant H3K27me3 occupancy, which in turn leads to defects in epiblast transformation events and subsequent implantation failure. Strikingly, manipulating Wnt signals can attenuate the pluripotency transition and H3K27me3 deposition defects in epiblasts and achieve up to a 9-fold increase in cloning efficiency. Finally, single-cell RNA-seq analysis reveals that Wnt inhibition markedly enhances the lineage developmental trajectories of SCNT blastocysts during peri-implantation development. Overall, these findings reveal diminished potentials of SCNT blastocysts for lineage specification and validate a critical peri-implantation barrier for SCNT embryos.

Bilineage embryo-like structure from EPS cells can produce live mice with tetraploid trophectoderm.

Self-organized blastoids from extended pluripotent stem (EPS) cells possess enormous potential for investigating postimplantation embryo development and related diseases. However, the limited ability of postimplantation development of EPS-blastoids hinders its further application. In this study, single-cell transcriptomic analysis indicated that the "trophectoderm (TE)-like structure" of EPS-blastoids was primarily composed of primitive endoderm (PrE)-related cells instead of TE-related cells. We further identified PrE-like cells in EPS cell culture that contribute to the blastoid formation with TE-like structure. Inhibition of PrE cell differentiation by inhibiting MEK signaling or knockout of Gata6 in EPS cells markedly suppressed EPS-blastoid formation. Furthermore, we demonstrated that blastocyst-like structures reconstituted by combining the EPS-derived bilineage embryo-like structure (BLES) with either tetraploid embryos or tetraploid TE cells could implant normally and develop into live fetuses. In summary, our study reveals that TE improvement is critical for constructing a functional embryo using stem cells in vitro.

[Regulatory effects and mechanisms of branched chain amino acids and metabolic intermediates on insulin resistance].

Branched chain amino acids, as essential amino acids, can be used to synthesize nitrogen-containing compounds and also act as signal molecules to regulate substance metabolism. Studies have shown that the elevated level of branched chain amino acids is closely related to insulin resistance and type 2 diabetes. It can affect insulin signal transduction by activating mammalian target of rapamycin (mTOR) signal pathway, and regulate insulin resistance by damaging lipid metabolism and affecting mitochondrial function. In addition, abnormal catabolism of branched amino acids can lead to the accumulation of metabolic intermediates, such as branched chain α-keto acids, 3-hydroxyisobutyrate and ß-aminoisobutyric acid. Branched chain α-keto acids and 3-hydroxyisobutyrate can induce insulin resistance by affecting insulin signaling pathway and damaging lipid metabolism. ß-aminoisobutyric acid can improve insulin resistance by reducing lipid accumulation and inflammatory reaction and enhancing fatty acid oxidation. This paper systematically reviewed the regulatory effects and mechanisms of branched chain amino acids and their metabolic intermediates on insulin resistance, which will provide a new direction for the prevention and treatment of insulin resistance and type 2 diabetes.

Resetting histone modifications during human prenatal germline development.

Histone modifications play critical roles in regulating gene expression and present dynamic changes during early embryo development. However, how they are reprogrammed during human prenatal germline development has not yet been elucidated. Here, we map the genome-wide profiles of three key histone modifications in human primordial germ cells (hPGCs) from weeks 8 to 23 of gestation for the first time by performing ULI-NChIP-seq. Notably, H3K4me3 exhibits a canonical promoter-enriched pattern, though with relatively lower enrichment, and is positively correlated with gene expression in globally hypomethylated hPGCs. In addition, H3K27me3 presents very low enrichment but plays an important role in not only dynamically governing specific bivalent promoters but also impeding complete X chromosome reactivation in female hPGCs. Given the activation effects of both global DNA demethylation and H3K4me3 signals, repressive H3K9me3 and H3K27me3 marks are jointly responsible for the paradoxical regulation of demethylation-resistant regions in hPGCs. Collectively, our results provide a unique roadmap of three core histone modifications during hPGC development, which helps to elucidate the architecture of germ cell reprogramming in an extremely hypomethylated DNA environment.

[Lipid metabolic intermediates regulate skeletal muscle insulin sensitivity].

Skeletal muscle is the largest organ of human body, which completes 80%-90% of glucose intake stimulated by insulin, and is closely related to the occurrence and development of insulin resistance (IR). Skeletal muscle is one of the main places of lipid metabolism, and lipid metabolites participate in skeletal muscle metabolism as signal molecules. Fatty acids regulate skeletal muscle insulin sensitivity through insulin signaling pathway, inflammatory response and mitochondrial function. Saturated fatty acids (SFAs) induce insulin resistance by impairing insulin signal transduction, inducing mitochondrial dysfunction and inflammatory response, while unsaturated fatty acids reverse the adverse effects of SFAs and ameliorate IR by enhancing insulin signal transduction and anti-inflammatory effect. In addition, disorders of lipid metabolism in skeletal muscle cause accumulation of harmful metabolic intermediates, such as diacylglycerol, ceramide and long-chain acyl-coenzyme A, and induce IR by directly or indirectly damaging insulin signaling pathway. This article reviews the research progress of lipid metabolic intermediates regulating insulin sensitivity in skeletal muscle, which will help to better understand the pathogenesis of diabetes.

Maternal Ezh1/2 deficiency in oocyte delays H3K27me2/3 restoration and impairs epiblast development responsible for embryonic sub-lethality in mouse.

How maternal Ezh1 and Ezh2 function in H3K27 methylation in vivo in pre-implantation embryos and during embryonic development is not clear. Here, we have deleted Ezh1 and Ezh2 alone or simultaneously from mouse oocytes. H3K27me3 was absent in oocytes without Ezh2 alone, while both H3K27me2 and H3K27me3 were absent in Ezh1/Ezh2 (Ezh1/2) double knockout (KO) oocytes. The effects of Ezh1/2 maternal KO were inherited in zygotes and early embryos, in which restoration of H3K27me3 and H3K27me2 was delayed by the loss of Ezh2 alone or of both Ezh1 and Ezh2. However, the ablation of both Ezh1 and Ezh2, but not Ezh1 or Ezh2 alone, led to significantly decreased litter size due to growth retardation post-implantation. Maternal Ezh1/2 deficiency caused compromised H3K27me3 and pluripotent epiblast cells in late blastocysts, followed by defective embryonic development. By using RNA-seq, we examined crucial developmental genes in maternal Ezh1/2 KO embryos and identified 80 putatively imprinted genes. Maternal Ezh1/2-H3K27 methylation is inherited in offspring embryos and has a critical effect on fetal and placental development. Thus, this work sheds light on maternal epigenetic modifications during embryonic development.

Aberrant H3K4me3 modification of epiblast genes of extraembryonic tissue causes placental defects and implantation failure in mouse IVF embryos.

Assisted reproductive technology has been widely applied in the treatment of human infertility. However, accumulating evidence indicates that in vitro fertilization (IVF) is associated with a low pregnancy rate, placental defects, and metabolic diseases in offspring. Here, we find that IVF manipulation notably disrupts extraembryonic tissue-specific gene expression, and 334 epiblast (Epi)-specific genes and 24 Epi-specific transcription factors are abnormally expressed in extraembryonic ectoderm (ExE) of IVF embryos at embryonic day 7.5. Combined histone modification analysis reveals that aberrant H3K4me3 modification at the Epi active promoters results in increased expression of these genes in ExE. Importantly, we demonstrate that knockdown of the H3K4me3-recruited regulator Kmt2e, which is highly expressed in IVF embryos, greatly improves the development of IVF embryos and reduces abnormal gene expression in ExE. Our study therefore identifies that abnormal H3K4me3 modification in extraembryonic tissue is a major cause of implantation failure and abnormal placental development of IVF embryos.

Allele-specific H3K9me3 and DNA methylation co-marked CpG-rich regions serve as potential imprinting control regions in pre-implantation embryo.

Parental DNA methylation and histone modifications undergo distinct global reprogramming in mammalian pre-implantation embryos, but the landscape of epigenetic crosstalk and its effects on embryogenesis are largely unknown. Here we comprehensively analyse the association between DNA methylation and H3K9me3 reprogramming in mouse pre-implantation embryos and reveal that CpG-rich genomic loci with high H3K9me3 signal and DNA methylation level (CHM) are hotspots of DNA methylation maintenance during pre-implantation embryogenesis. We further profile the allele-specific epigenetic map with unprecedented resolution in gynogenetic and androgenetic embryos, respectively, and identify 1,279 allele-specific CHMs, including 19 known imprinting control regions (ICRs). Our study suggests that 22 ICR-like regions (ICRLRs) may regulate allele-specific transcription similarly to known ICRs, and five of them are confirmed to be important for mouse embryo development. Taken together, our study reveals the widespread existence of allele-specific CHMs and largely extends the scope of allele-specific regulation in mammalian pre-implantation embryos.

Melatonin supplementation in the culture medium rescues impaired glucose metabolism in IVF mice offspring.

Increasing evidence suggests that in vitro fertilization (IVF) may be associated with an increased risk of developing obesity and metabolic diseases later in life in the offspring. Notably, the addition of melatonin to culture medium may improve embryo development and prevent cardiovascular dysfunction in IVF adult mice. This study aimed to determine if melatonin supplementation in the culture medium can reverse impaired glucose metabolism in IVF mice offspring and the underlying mechanisms. Blastocysts used for transfer were generated by natural mating (control group) or IVF with or without melatonin (10-6  M) supplementation (mIVF and IVF group, respectively) in clinical-grade culture media. Here, we first report that IVF decreased hepatic expression of Fbxl7, which was associated with impaired glucose metabolism in mice offspring. Melatonin addition reversed the phenotype by up-regulating the expression of hepatic Fbxl7. In vitro experiments showed that Fbxl7 enhanced the insulin signaling pathway by degrading RhoA through ubiquitination and was up-regulated by transcription factor Foxa2. Specific knockout of Fbxl7 in the liver of adult mice, through tail intravenous injection of recombinant adeno-associated virus, impaired glucose tolerance, while overexpression of hepatic Fbxl7 significantly improved glucose tolerance in adult IVF mice. Thus, the data suggest that Fbxl7 plays an important role in maintaining glucose metabolism of mice, and melatonin supplementation in the culture medium may rescue the long-term risk of metabolic diseases in IVF offspring.

Altered sperm tsRNAs in aged male contribute to anxiety-like behavior in offspring.

Parental age at first pregnancy is increasing worldwide. The offspring of aged father has been associated with higher risk of several neuropsychiatric disorders, such as schizophrenia and autism, but the underlying mechanism remains elusive. Here we report that advanced paternal age in mice alters the profile of transfer RNA-derived small RNAs (tsRNAs). Injection of sperm tsRNAs from aged male mice into zygotes induced anxiety-like behaviors in F1 males. RNA sequencing of the cerebral cortex and hippocampus of those F1 male mice altered the gene expression of dopaminergic synapse and neurotrophin. tsRNAs from aged male mice injection also altered the neuropsychiatry-related gene expression in two-cell and blastocyst stage embryos. More importantly, the sperm tsRNA profile changes significantly during aging in human. The up-regulated sperm tsRNA target genes were involved in neurogenesis and nervous system development. These results suggest that aging-related changes of sperm tsRNA may contribute to the intergenerational transmission of behavioral traits.

Pre-pregnancy exposure to fine particulate matter (PM2.5) increases reactive oxygen species production in oocytes and decrease litter size and weight in mice.

Exposure of females to fine particulate matter ≤2.5 µm in diameter (PM2.5) prior to pregnancy could produce adverse impact on fertility and enhances susceptibility of the offspring to a variety of diseases. In the current study, female C57BL/6 mice (6 weeks of age) were exposed to either concentrated PM2.5 or filtered air (average PM2.5 concentration: 115.60 ± 7.77 vs. 14.07 ± 0.38 µg/m-3) using a whole-body exposure device for 12 weeks. Briefly, PM2.5 exposure decreased anti-Müllerian hormone level (613.40 ± 17.36 vs 759.30 ± 21.90 pg mL-1, P＜0.01) and increased reactive oxygen species (ROS) level (45.39 ± 0.82 vs 24.20 ± 0.85 arbitrary unit in fluorescence assay, P＜0.01) in oocytes. The exposure increased oocyte degeneration rate (21.5% vs 5.1%, respectively (P＜0.01) and decreased the 2-cell formation rate (71.9% vs 86.0%, P < 0.01). Transcriptome profiling using RNA sequencing showed wide spectrum of abnormal expression of genes, particularly those involved in regulating the mitochondrial respiratory complex in oocytes and metabolic processes in blastocysts. The exposure decreased litter size (6 ± 0.37 vs 7 ± 0.26, P＜0.05) and weight (1.18 ± 0.02 vs 1.27 ± 0.02 g, P＜0.01). In summary, PM2.5 exposure decreased female fertility, possibly through increased ROS production in oocytes and metabolic disturbances in developing embryos. The cause-effect relationship, however, requires further investigation.

Precise allele-specific genome editing by spatiotemporal control of CRISPR-Cas9 via pronuclear transplantation.

Gene-targeted animal models that are generated by injecting Cas9 and sgRNAs into zygotes are often accompanied by undesired double-strand break (DSB)-induced byproducts and random biallelic targeting due to uncontrollable Cas9 targeting activity. Here, we establish a parental allele-specific gene-targeting (Past-CRISPR) method, based on the detailed observation that pronuclear transfer-mediated cytoplasmic dilution can effectively terminate Cas9 activity. We apply this method in embryos to efficiently target the given parental alleles of a gene of interest and observed little genomic mosaicism because of the spatiotemporal control of Cas9 activity. This method allows us to rapidly explore the function of individual parent-of-origin effects and to construct animal models with a single genomic change. More importantly, Past-CRISPR could also be used for therapeutic applications or disease model construction.

Genome transfer for the prevention of female infertility caused by maternal gene mutation.

Poor oocyte quality is associated with early embryo developmental arrest and infertility. Maternal gene plays crucial roles in the regulation of oocyte maturation, and its mutation is a common cause of female infertility. However, how to improve oocyte quality and develop effective therapy for maternal gene mutation remains elusive. Here, we use Zar1 as an example to assess the feasibility of genome transfer to cure maternal gene mutation-caused female infertility. We first discover that cytoplasmic deficiency primarily leads to Zar1-null embryo developmental arrest by disturbing maternal transcript degradation and minor zygotic genome activation (ZGA) during the maternal-zygotic transition. We next perform genome transfer at the oocyte (spindle transfer or polar body transfer) and zygote (early pronuclear transfer or late pronuclear transfer) stages to validate the feasibility of preventing Zar1 mutation-caused infertility. We finally demonstrate that genome transfer either at the oocyte or at the early pronuclear stage can support normal preimplantation embryo development and produce live offspring. Moreover, those pups grow to adulthood and show normal fertility. Therefore, our findings provide an effective basis of therapies for the treatment of female infertility caused by maternal gene mutation.

Identification and rescue of a novel TUBB8 mutation that causes the first mitotic division defects and infertility.

PURPOSE: Tubulin beta eight class VIII (TUBB8) is essential for oogenesis, fertilization, and pre-implantation embryo development in human. Although TUBB8 mutations were recently discovered in meiosis-arrested oocytes of infertile females, there is no effective therapy for this gene mutation caused infertility. Our study aims to further reveal the infertility-causing gene mutations in the patient's family and to explore whether the infertility could be rescued by optimizing the conditions of embryo culture and finally achieve the purpose of making the patient pregnant. METHODS: Whole-exome sequence analysis and Sanger sequencing were performed on patients' family members to screen and identify candidate mutant genes. Construction of plasmids, in vitro transcription, microinjection of disease-causing gene cRNA, and immunofluorescence staining were used to recapitulate the infertility phenotype observed in patients and to understand the pathogenic principles. Simultaneously, overexpression of mutant and wild-type cRNA of the candidate gene in mouse oocytes at either germinal vesicle (GV) or metaphase II (MII) stage was performed in the rescue experiment. RESULTS: We first identified a novel heritable TUBB8 mutation (c.1041C>A: p.N347K) in the coding region which specifically affects the first mitosis and causes the developmental arrest of early embryos in a three-generation family. We further demonstrated that TUBB8 mutation could lead to abnormal spindle assemble. And moreover, additional expression of wild-type TUBB8 cRNA in the mouse oocytes in which the mutant TUBB8 were expressed can successfully rescue the developmental defects of resulting embryo and produce full-term offspring. CONCLUSIONS: Our study not only defines a novel mutation of TUBB8 causing the early cleavage arrest of embryos, but also provides an important basis for treating such female infertility in the future.

Distinct H3K9me3 and DNA methylation modifications during mouse spermatogenesis.

DNA methylation and histone modifications critically regulate the expression of many genes and repeat regions during spermatogenesis. However, the molecular details of these processes in male germ cells remain to be addressed. Here, using isolated murine sperm cells, ultra-low-input native ChIP-Seq (ULI-NChIP-Seq), and whole genome bisulfite sequencing (WGBS), we investigated genome-wide DNA methylation patterns and histone 3 Lys-9 trimethylation (H3K9me3) modifications during mouse spermatogenesis. We found that DNA methylation and H3K9me3 have distinct sequence preferences and dynamics in promoters and repeat elements during spermatogenesis. H3K9me3 modifications in histones at gene promoters were highly enriched in round spermatids. H3K9me3 modification on long terminal repeats (LTRs) and long interspersed nuclear elements (LINEs) was involved in silencing active transcription from these regions in conjunction with reestablishment of DNA methylation. Furthermore, H3K9me3 remodeling on the X chromosome was involved in meiotic sex chromosome inactivation and in partial transcriptional reactivation of sex chromosomes in spermatids. Our findings also revealed the DNA methylation patterns and H3K9me3 modification profiles of paternal and maternal germline imprinting control regions (gICRs) during spermatogenesis. Taken together, our results provide a genome-wide map of H3K9me3 modifications during mouse spermatogenesis that may be helpful for understanding male reproductive disorders.

Inhibition of Aberrant DNA Re-methylation Improves Post-implantation Development of Somatic Cell Nuclear Transfer Embryos.

Somatic cell nuclear transfer (SCNT) enables cloning of differentiated cells by reprogramming their nuclei to a totipotent state. However, successful full-term development of SCNT embryos is a low-efficiency process and arrested embryos frequently exhibit epigenetic abnormalities. Here, we generated genome-wide DNA methylation maps from mouse pre-implantation SCNT embryos. We identified widespread regions that were aberrantly re-methylated, leading to mis-expression of genes and retrotransposons important for zygotic genome activation. Inhibition of DNA methyltransferases (Dnmts) specifically rescued these re-methylation defects and improved the developmental capacity of cloned embryos. Moreover, combining inhibition of Dnmts with overexpression of histone demethylases led to stronger reductions in inappropriate DNA methylation and synergistic enhancement of full-term SCNT embryo development. These findings show that excessive DNA re-methylation is a potent barrier that limits full-term development of SCNT embryos and that removing multiple epigenetic barriers is a promising approach to achieve higher cloning efficiency.