Can Reprogramming of Overall Epigenetic Memory and Specific Parental Genomic Imprinting Memory within Donor Cell-Inherited Nuclear Genome be a Major Hindrance for the Somatic Cell Cloning of Mammals? – A Review

Epigenetic Iinsights into the Senescence of Porcine Fetal Fibroblasts induced by Passaging

Epigenetic status of fetal fibroblasts (FFs) is one of the crucial factors accounted for the success of somatic cell nuclear transfer and gene editing, which might inevitably be affected by passaging. But few systematic studies have been performed on the epigenetic status of passaged aging cells. Therefore, FFs from large white pig were in vitro passaged to the 5, 10, and 15 (F5, F10, and F15) passages in the present study to investigate the potential alteration of epigenetic status. Results indicated the senescence of FFs occurs with the passaging, as assessed by the weakened growth rate, increased β-gal expression, and so on. For the epigenetic status of FFs, the higher level both of DNA methylation and H3K4me1, H3K4me2, H3K4me3 was observed at F10, but the lowest level was observed at F15. However, the fluorescence intensity of m6A was significantly higher in F15, but lower (p < 0.05) in F10, and the related mRNA expression in F15 was significantly higher than F5. Further, RNA-Seq indicated a considerable difference in the expression pattern of F5, F10, and F15 FFs. Among differentially expressed genes, not only the genes involved in cell senescence were changed, but also the upregulated expression of Dnmt1, Dnmt3b, Tet1 and dysregulated expression of histone methyltransferases-related genes were detected in F10 FFs. In addition, most genes related to m6A such as METTL3, YTHDF2, and YTHDC1 were significantly different in F5, F10, and F15 FFs. In conclusion, the epigenetic status of FFs was affected by being passaged from F5 to F15.

Interspecific Nuclear Transfer Blastocysts Reconstructed from Arabian Oryx Somatic Cells and Domestic Cow Ooplasm

Cloning, commonly referred to as somatic cell nuclear transfer (SCNT), is the technique of enucleating an oocyte and injecting a somatic cell into it. This study was carried out with interspecific SCNT technology to clone the Arabian Oryx utilizing the oryx's fibroblast cells and transfer it to the enucleated oocytes of a domestic cow. The recipient oocytes were extracted from the cows that had been butchered. Oryx somatic nuclei were introduced into cow oocytes to produce embryonic cells. The study was conducted on three groups, Oryx interspecific somatic cell nuclear transfer into enucleated oocytes of domestic cows, cow SCNT "the same bovine family species", used as a control group, and in vitro fertilized (IVF) cows to verify all media used in this work. The rates of different embryo developmental stages varied slightly (from 1- cell to morula stage). Additionally, the oryx interspecies Somatic cell nuclear transfer blastocyst developmental rate (9.23%) was comparable to that of cow SCNT (8.33%). While the blastula stage rate of the (IVF) cow embryos exhibited a higher cleavage rate (42%) in the embryo development stage. The results of this study enhanced domestic cow oocytes' ability to support interspecific SCNT cloned oryx, and generate a viable embryo that can advance to the blastula stage.

A review on the epigenetics modifications to nanomaterials in humans and animals: novel epigenetic regulator

In the nanotechnology era, nanotechnology applications have been intensifying their prospects to embrace all the vigorous sectors persuading human health and animal. The safety and concerns regarding the widespread use of engineered nanomaterials (NMA) and their potential effect on human health still require further clarification. Literature elucidated that NMA exhibited significant adverse effects on various molecular and cellular alterations. Epigenetics is a complex process resulting in the interactions between an organism’s environment and genome. The epigenetic modifications, including histone modification and DNA methylation, chromatin structure and DNA accessibility alteration, regulate gene expression patterns. Disturbances of epigenetic markers induced by NMA might promote the sensitivity of humans and animals to several diseases. Also, this paper focus on the epigenetic regulators of some dietary nutrients that have been confirmed to stimulate the epigenome and, more exactly, DNA histone modifications and non-histone proteins modulation by acetylation, and phosphorylation inhibition, which counteracts oxidative stress generations. The present review epitomizes the recent evidence of the potential effects of NMA on histone modifications, in addition to in vivo and in vitro cytosine DNA methylation and its toxicity. Furthermore, the part of epigenetic fluctuations as possible translational biomarkers for uncovering untoward properties of NMA is deliberated.

Effect of serum starvation and contact inhibition on dermal fibroblast cell cycle synchronization in two species of wild felids and domestic cat

Cell cycle synchronization of donor cells is an important step in mammalian somatic cell nuclear transfer (SCNT). This study was designed to compare the efficiency of serum starvation (Ss) and contact inhibition (cI) on cell cycle synchronization of jaguarundi, manul, and domestic cat skin fibroblasts, in the production of G0/G1 cells suitable for SCNT in felids. Ss was performed after the growing (G) cells reached 40–50% (G50+Ss), 60–70% (G70+Ss) and full confluency (Fc), i.e. in association with cI (cI+Ss). Frozen-thawed cells were cultured to the given state of confluency (d0; controls), and subjected to Ss or cI for 1, 3, and 5 days (d). In manul, the effect of Ss on arresting fibroblasts in the G0/G1 phase was noted after just 1d of culture at G70 confluence, while G50+Ss and cI+Ss were effective after 5d of treatment. In jaguarundi, 1–5d of G50+Ss and 5d of G70+Ss increased the percentage of G0/G1 cells versus d0 (P<0.01), with 5d of G70+Ss producing more (P<0.05) quiescent cells than after the same period of G50+Ss, cI+Ss and cI. In the domestic cat, Ss was efficient only after 3 and 5d of G50+Ss. In all species, cI alone failed to increase the proportion of G0/G1 cells compared to d0, however in the domestic cat, 5d of cI was more efficient than the same period of G50+Ss. In jaguarundi, >93% of cells were already in G0/G1 phase at d0 of Fc, suggesting that culture to Fc could be also a valuable method for fibroblast cell cycle synchronization in this species. In contrast to cI, prolonged Ss generated cell loss and could induce apoptosis and/or necrosis. In conclusion, Ss was the more efficient method for skin fibroblast cell cycle synchronization at the G0/G1 phase in manul, jaguarundi and the domestic cat. The response of cells to the treatments was species-specific, depending on cell confluence and duration of culture. This research may find application in preparing donor karyoplasts for SCNT in felids.

A diverse English keyword search reveals the value of scriptaid treatment for porcine embryo development following somatic cell nuclear transfer

CONTEXT

Incomplete epigenetic reprogramming of histone deacetylation (HDAC) is one of the main reasons for the low efficiency of somatic cell nuclear transfer (SCNT). Scriptaid is a synthetic HDAC inhibitor (HDACi) that may improve the efficiency of porcine SCNT.

AIMS

This study aimed to determine whether scriptaid increases the number of blastocyst cells or the cleavage rate.

METHODS

We conducted a meta-analysis of the pertinent literature published over the past decade.

KEY RESULTS

A total of 73 relevant papers were retrieved using a diverse English keyword search, and 11 articles were used for the meta-analysis. Scriptaid was positively correlated with blastocyst rate but had no effect on cleavage rate or blastocyst cell number. A subgroup analysis of blastocyst cell number showed that the staining method was the source of the heterogeneity.

CONCLUSIONS

In SCNT embryos, scriptaid treatment after activation can promote embryonic development, but there may be adverse effects on early development.

IMPLICATIONS

HDACi research should focus on SCNT birth efficiency.

The role of passage numbers of donor cells in the development of Arabian Oryx – Cow interspecific somatic cell nuclear transfer embryos

The cloning between different animals known as interspecific somatic cell nuclear transfer (iSCNT) was carried out for endangered species. The iSCNT has been characterized by a poor success rate due to several factors that influence the formation of the SCNT in various cytoplasms. The cell cycle of the transferred somatic cell, the passage number of the cultured somatic cell, the mitochondria oocytes, and their capabilities are among these factors. This study investigates the role of the passage number of the Arabian Oryx somatic cell culture when transplanted to an enucleated domestic cow oocyte and embryo development in vitro. The fibroblast somatic cell of the Arabian Oryx was cultured for several passage lanes (3–13). The optimal passage cell number was found to be 10–13 Oryx cell lines that progressed to various cell stages up to the blastula stage. There was some variation between the different passage numbers of the oryx cell line. The 3–9 cell line did not show a good developmental stage. These could be attributed to several factors that control the iSCNT as stated by several investigators. More investigation is needed to clarify the role of factors that affect the success rate for the iSCNT.

Effects of Trichostatin A on the Timing of the First Cleavage and In Vitro Developmental Potential of Bovine Somatic Cell Nuclear Transfer Embryos

This study examined the relationship between the timing of the first cleavage and in vitro development of bovine somatic cell nuclear transfer (SCNT) embryos treated with trichostatin A (TSA). SCNT embryos were visually assessed at 22, 26, and 48 hours after activation. Each embryo with two or more distinct blastomeres was transferred into a microwell and cultured until day 7. Irrespective of TSA treatment, approximately half of the cleaved embryos were observed at 22 hours, and a significantly higher blastocyst formation rate was shown in the SCNT embryos cleaved at 22 hours than those cleaved at ≥26 hours. The blastocyst formation rate of TSA-treated embryos cleaved at 22 hours (80%) was slightly higher than that of the control embryos (70%). In addition, interferon-τ (IFN-τ) expression was significantly lower in control SCNT embryos and late-cleaving (>26 hours) TSA-treated embryos than in in vitro fertilized (IVF) embryos. However, a significant difference was not observed between TSA-treated SCNT embryos cleaved at 22 and 26 hours, and IVF embryos. These results suggest that TSA treatment has no influence on the timing of the first cleavage of SCNT embryos; however, it slightly improves the blastocyst formation rate and the expression level of IFN-τ in early-cleaving embryos.

Strategies to Improve the Efficiency of Somatic Cell Nuclear Transfer

Mammalian oocytes can reprogram differentiated somatic cells into a totipotent state through somatic cell nuclear transfer (SCNT), which is known as cloning. Although many mammalian species have been successfully cloned, the majority of cloned embryos failed to develop to term, resulting in the overall cloning efficiency being still low. There are many factors contributing to the cloning success. Aberrant epigenetic reprogramming is a major cause for the developmental failure of cloned embryos and abnormalities in the cloned offspring. Numerous research groups attempted multiple strategies to technically improve each step of the SCNT procedure and rescue abnormal epigenetic reprogramming by modulating DNA methylation and histone modifications, overexpression or repression of embryonic-related genes, etc. Here, we review the recent approaches for technical SCNT improvement and ameliorating epigenetic modifications in donor cells, oocytes, and cloned embryos in order to enhance cloning efficiency.

Technical, Biological and Molecular Aspects of Somatic Cell Nuclear Transfer – A Review

Since the announcement of the birth of the first cloned mammal in 1997, Dolly the sheep, 24 animal species including laboratory, farm, and wild animals have been cloned. The technique for somatic cloning involves transfer of the donor nucleus of a somatic cell into an enucleated oocyte at the metaphase II (MII) stage for the generation of a new individual, genetically identical to the somatic cell donor. There is increasing interest in animal cloning for different purposes such as rescue of endangered animals, replication of superior farm animals, production of genetically engineered animals, creation of biomedical models, and basic research. However, the efficiency of cloning remains relatively low. High abortion, embryonic, and fetal mortality rates are frequently observed. Moreover, aberrant developmental patterns during or after birth are reported. Researchers attribute these abnormal phenotypes mainly to incomplete nuclear remodeling, resulting in incomplete reprogramming. Nevertheless, multiple factors influence the success of each step of the somatic cloning process. Various strategies have been used to improve the efficiency of nuclear transfer and most of the phenotypically normal born clones can survive, grow, and reproduce. This paper will present some technical, biological, and molecular aspects of somatic cloning, along with remarkable achievements and current improvements.

Ex Situ Conservation and Genetic Rescue of Endangered Polish Cattle and Pig Breeds with the Aid of Modern Reproductive Biotechnology – A Review

The development and optimization of reproductive biotechnology – specifically semen cryopreservation, spermatological diagnostics, and intraspecies cloning by somatic cell nuclear transfer (SCNT) – have become essential techniques to conserve the genetic resources and establish genetic reserves of endangered or vanishing native Polish livestock breeds. Moreover, this biotechnology is necessary for perpetuating biological diversity and enhancing genetic variability as well as for restoring and reintroducing breeds into anthropogenic agricultural ecosystems. On the one hand, the purpose of our paper is to interpret recent efforts aimed at the ex situ conservation of native cattle and pig breeds. On the other, it emphasizes the prominent role played by the National Research Institute of Animal Production (NRIAP) in maintaining biodiversity in agricultural environmental niches. Furthermore, our paper provides an overview of the conventional and modern strategies of the banking and cryopreservation of germplasm-carrier biological materials and somatic cell lines, spermatological diagnostics, and semen-based and SCNT-mediated assisted reproductive technologies (ART s). These are the most reliable and powerful tools for ex situ protection of the genetic resources of endangered breeds of livestock, especially cattle and pigs.

Interleukin 17D Enhances the Developmental Competence of Cloned Pig Embryos by Inhibiting Apoptosis and Promoting Embryonic Genome Activation

Simple Summary

The cloning technique is important for animal husbandry and biomedicine because it can be used to clone superior breeding livestock and produce multipurpose genetically modified animals. However, the success rate of cloning currently is very low due to the low developmental efficiency of cloned embryos, which limits the application of cloning. The low developmental competence is related to the excessive cell death in cloned embryos. Interleukin 17D (IL17D) is required for the normal development of mouse embryos by inhibiting cell death. This study aimed to investigate whether IL17D can improve cloned pig embryo development by inhibiting cell death. Addition of IL17D protein to culture medium decreased the cell death level and improved the developmental ability of cloned pig embryos. IL17D treatment enhanced cloned pig embryo development by regulating cell death-associated gene pathways and promoting genome-wide gene expression, which is probably via up-regulating the expression of a gene called GADD45B. This study provided a new approach to improve the pig cloning efficiency by adding IL17D protein to the culture medium of cloned pig embryos.

Abstract

Cloned animals generated by the somatic cell nuclear transfer (SCNT) approach are valuable for the farm animal industry and biomedical science. Nevertheless, the extremely low developmental efficiency of cloned embryos hinders the application of SCNT. Low developmental competence is related to the higher apoptosis level in cloned embryos than in fertilization-derived counterparts. Interleukin 17D (IL17D) expression is up-regulated during early mouse embryo development and is required for normal development of mouse embryos by inhibiting apoptosis. This study aimed to investigate whether IL17D plays roles in regulating pig SCNT embryo development. Supplementation of IL17D to culture medium improved the developmental competence and decreased the cell apoptosis level in cloned porcine embryos. The transcriptome data indicated that IL17D activated apoptosis-associated pathways and promoted global gene expression at embryonic genome activation (EGA) stage in treated pig SCNT embryos. Treating pig SCNT embryos with IL17D up-regulated expression of GADD45B, which is functional in inhibiting apoptosis and promoting EGA. Overexpression of GADD45B enhanced the developmental efficiency of cloned pig embryos. These results suggested that IL17D treatment enhanced the developmental ability of cloned pig embryos by suppressing apoptosis and promoting EGA, which was related to the up-regulation of GADD45B expression. This study demonstrated the roles of IL17D in early development of porcine SCNT embryos and provided a new approach to improve the developmental efficiency of cloned porcine embryos.

The Resurrection of Mabrokan: Production of Multiple Cloned Offspring from Decade-Old Vitrified Tissue Collected from a Deceased Champion Show Camel

Somatic cell nuclear transfer (SCNT) provides a unique opportunity to reproduce animals with superior genetics. Viable cell lines are usually established from tissues collected by biopsy from living animals in the SCNT program. In the present study, tissues were collected and preserved from a suddenly deceased champion camel. We established cell lines from these decade-old tissues and used them as nuclear donors. After 42 h of in vitro maturation, 68.00 ± 2.40% of oocytes reached the metaphase II (M II) stage while 87.31 ± 2.57% in vivo collected oocytes were matured at collection (p < 0.05). We observed a higher blastocyst formation rate when in vivo matured oocytes (43.45 ± 2.07%) were used compared to in vitro matured oocytes (21.52 ± 1.74%). The live birth rate was 6.45% vs. 16.67% for in vitro and in vivo matured oocytes, respectively. Microsatellite analysis of 13 camel loci revealed that all the SCNT-derived offspring were identical to each other and with their somatic cell donor. The present study succeeded in the resurrection of 11 healthy offspring from the decade-old vitrified tissues of a single somatic cell donor individual using both in vitro and in vivo matured oocytes.

Effects of Incubation Time and Method of Cell Cycle Synchronization on Collared Peccary Skin-Derived Fibroblast Cell Lines

The success of cloning by somatic cell nuclear transfer depends on the efficiency of nuclear reprogramming, with the cycle stage of the donor cell playing a crucial role. Therefore, the aim was to evaluate three different approaches for cell cycle synchronization: (i) serum starvation (SS) for 1 to 4 days, (ii) contact inhibition (CI) for 1 to 3 days, and (iii) using cell cycle regulatory inhibitors (dimethyl sulfoxide, cycloheximide, cytochalasin B, or 6-dimethylaminopurine) for 1 and 2 days, in terms of their effects on synchronization in G0/G1 phases and viability of collared peccary skin fibroblasts. Flow cytometry analysis revealed that SS for 4 days (79.0% ± 1.6) and CI for 3 days (78.0% ± 1.4) increased the percentage of fibroblasts in G0/G1 compared to growing cells GC (68.1% ± 8.6). However, SS for 3 and 4 days reduced the viability evaluated by differential staining (81.4% ± 0.03 and 81.6% ± 0.06) compared to growing cells (GC, 95.9% ± 0.06). CI did not affect the viability at any of the analyzed time intervals. No cell cycle inhibitors promoted synchronization in G0/G1. These results indicate that CI for 3 days was the most efficient method for cell cycle synchronization in peccary fibroblasts.

Generation of Monogenetic Cattle by Different Techniques of Embryonic Cell and Somatic Cell Cloning – Their Application to Biotechnological, Agricultural, Nutritional, Biomedical and Transgenic Research – A Review

The development of effective approaches for not only the in vitro maturation (IVM) of heifer/cow oocytes and their extracorporeal fertilization (IVF) but also the non-surgical collection and transfer of bovine embryos has given rise to optimizing comprehensive in vitro embryo production (IVP) technology and improving other assisted reproductive technologies (ART s), such as cattle cloning by embryo bisection, embryonic cell nuclear transfer (ECNT) and somatic cell nuclear transfer (SCNT). The primary goal of the present paper is to demonstrate the progress and achievements in the strategies utilized for embryonic cell cloning and somatic cell cloning in cattle. Moreover, the current article is focused on recognizing and identifying the suitability and reliability of bovine cloning techniques for nutritional biotechnology, agri-food and biopharmaceutical industry, biomedical and transgenic research and for the genetic rescue of endangered or extinct breeds and species of domesticated or wild-living artiodactyl mammals (even-toed ungulates) originating from the family Bovidae.

Generating Cloned Goats by Somatic Cell Nuclear Transfer-Molecular Determinants and Application to Transgenics and Biomedicine

The domestic goat (Capra aegagrus hircus), a mammalian species with high genetic merit for production of milk and meat, can be a tremendously valuable tool for transgenic research. This research is focused on the production and multiplication of genetically engineered or genome-edited cloned specimens by applying somatic cell nuclear transfer (SCNT), which is a dynamically developing assisted reproductive technology (ART). The efficiency of generating the SCNT-derived embryos, conceptuses, and progeny in goats was found to be determined by a variety of factors controlling the biological, molecular, and epigenetic events. On the one hand, the pivotal objective of our paper was to demonstrate the progress and the state-of-the-art achievements related to the innovative and highly efficient solutions used for the creation of transgenic cloned does and bucks. On the other hand, this review seeks to highlight not only current goals and obstacles but also future challenges to be faced by the approaches applied to propagate genetically modified SCNT-derived goats for the purposes of pharmacology, biomedicine, nutritional biotechnology, the agri-food industry, and modern livestock breeding.

Genome stabilization by RAD51-stimulatory compound 1 enhances efficiency of somatic cell nuclear transfer-mediated reprogramming and full-term development of cloned mouse embryos

OBJECTIVES

The genetic instability and DNA damage arise during transcription factor-mediated reprogramming of somatic cells, and its efficiency may be reduced due to abnormal chromatin remodelling. The efficiency in somatic cell nuclear transfer (SCNT)-mediated reprogramming is also very low, and it is caused by development arrest of most reconstituted embryos.

MATERIALS AND METHODS

Whether the repair of genetic instability or double-strand breaks (DSBs) during SCNT reprogramming may play an important role in embryonic development, we observed and analysed the effect of Rad 51, a key modulator of DNA damage response (DDR) in SCNT-derived embryos.

RESULTS

Here, we observed that the activity of Rad 51 is lower in SCNT eggs than in conventional IVF and found a significantly lower level of DSBs in SCNT embryos during reprogramming. To address this difference, supplementation with RS-1, an activator of Rad51, during the activation of SCNT embryos can increase RAD51 expression and DSB foci and thereby increased the efficiency of SCNT reprogramming. Through subsequent single-cell RNA-seq analysis, we observed the reactivation of a large number of genes that were not expressed in SCNT-2-cell embryos by the upregulation of DDR, which may be related to overcoming the developmental block. Additionally, there may be an independent pathway involving histone demethylase that can reduce reprograming-resistance regions.

CONCLUSIONS

This technology can contribute to the production of comparable cell sources for regenerative medicine.

Inhibition of Suv39h1/2 expression improves the early development of Debao porcine somatic cell nuclear transfer embryos

Suppressor of variegation 3-9 homolog (Suv39h)1 and 2, Histone H3 lysine 9 trimethylation (H3K9me3)-specific methyltransferases, are mainly involved in regulating the dynamic changes of H3K9me3. Regulating Suv39h expression influences the early development of mice somatic cell nuclear transfer (SCNT) embryos, there are few reports concerning their features in domestic animals. The aim of the present study was to characterize the Suv39h function in early development of Debao porcine SCNT embryos. The global level of H3K9me3 and the expression profiles of Suv39h1/2 in porcine early embryos were analysed by immunohistochemistry and qRT-PCR methods, respectively. Their roles in cell proliferation and histone modification of Debao porcine foetal fibroblast cells (PFFs), and developmental competence of porcine SCNT embryos were investigated by shRNA technology. The methylation levels of H3K9me3 and the expression patterns of Suv39h1 and Suv39h2 were similar (p < .05), and both of them displayed higher levels in Debao porcine SCNT embryos compared with that in PA embryos. The global levels of H3K9me3 and the expressions of G9a, HDAC1 and DNMT1 were decreased by combined inhibition of Suv39h1 and Suv39h2 (p < .05), while the expression of HAT1 was increased (p < .05). Downregulation of Suv39h1/2 also promoted cell proliferation and resulted in a significant increase in the expression of CyclinA2, CyclinB and PCNA in PFFs (p < .05). Furthermore, the use of donor somatic nuclei which depleted H3K9me3 by inhibiting Suv39h1/2 expression markedly increased the cleavage rate, the blastocyst rate and the total cell number of blastocysts of Debao porcine SCNT embryos (p < .05). Altogether, the above results indicate that H3K9me3 levels and Suv39h1/2 expressions display similar patterns in porcine early embryo, and low levels of them are critical to cell proliferation of PFFs and early development of SCNT embryos.

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.

Extranuclear Inheritance of Mitochondrial Genome and Epigenetic Reprogrammability of Chromosomal Telomeres in Somatic Cell Cloning of Mammals

The effectiveness of somatic cell nuclear transfer (SCNT) in mammals seems to be still characterized by the disappointingly low rates of cloned embryos, fetuses, and progeny generated. These rates are measured in relation to the numbers of nuclear-transferred oocytes and can vary depending on the technique applied to the reconstruction of enucleated oocytes. The SCNT efficiency is also largely affected by the capability of donor nuclei to be epigenetically reprogrammed in a cytoplasm of reconstructed oocytes. The epigenetic reprogrammability of donor nuclei in SCNT-derived embryos appears to be biased, to a great extent, by the extranuclear (cytoplasmic) inheritance of mitochondrial DNA (mtDNA) fractions originating from donor cells. A high frequency of mtDNA heteroplasmy occurrence can lead to disturbances in the intergenomic crosstalk between mitochondrial and nuclear compartments during the early embryogenesis of SCNT-derived embryos. These disturbances can give rise to incorrect and incomplete epigenetic reprogramming of donor nuclei in mammalian cloned embryos. The dwindling reprogrammability of donor nuclei in the blastomeres of SCNT-derived embryos can also be impacted by impaired epigenetic rearrangements within terminal ends of donor cell-descended chromosomes (i.e., telomeres). Therefore, dysfunctions in epigenetic reprogramming of donor nuclei can contribute to the enhanced attrition of telomeres. This accelerates the processes of epigenomic aging and replicative senescence in the cells forming various tissues and organs of cloned fetuses and progeny. For all the above-mentioned reasons, the current paper aims to overview the state of the art in not only molecular mechanisms underlying intergenomic communication between nuclear and mtDNA molecules in cloned embryos but also intrinsic determinants affecting unfaithful epigenetic reprogrammability of telomeres. The latter is related to their abrasion within somatic cell-inherited chromosomes.

Elimination of stress factors by continuous embryo culture and its influence on in vitro fertilization outcomes

Recently, infertility has become one of the most important endemic conditions, affecting approximately 15-20 % of couples worldwide. Among others, the careerist lifestyle, the increasing maternal age and the parallel increment in the aneuploidy rate of embryos play a crucial role in this phenomenon. In this study, embryological parameters and pregnancy outcomes were investigated in IVF cycles using either sequential embryo culture or a single step culture system. By sequential media, oocytes/embryos are needlessly exposed to the potentially negative effects of light exposure, temperature decrement and altered oxygen tension. In comparison with sequential media, single step media induced 1.28, 1.21 and 1.21-fold increments in implantation, biochemical pregnancy and clinical pregnancy rates, respectively. Pregnancy outcomes showed strong maternal age-dependency, so the difference between the two investigated culture systems was equalized by the increasing maternal ages (35-44 years) and the supposed incidence of embryo aneuploidy. Nevertheless, the significant enlargements in the outcomes of the younger ages (25-34) induced by the single step cultures suggest that, beside the resultant maternal aneuploidy, aneuploidy (reduced pregnancy rates) may evolve from exposure to the mentioned environmental stress factors.

A blastocyst biopsy approach for preimplantation genetic diagnosis technique that affects the expression of SNAP-α in mice

Preimplantation genetic diagnosis (PGD) is a technique that is commonly used during assisted reproduction in the clinics to eliminate genetically abnormal embryos before implantation. The blastomere biopsy technique has risks related to the embryo, but blastocyst biopsy has not been systematically evaluated in relation to effects after birth, and the resulting offspring have not been followed up on. We designed a series of experiments to evaluate the risk of blastocyst biopsy on the resulting progeny. Mice were divided into a PGD group and a control group. The former was the progeny of mice that underwent blastocyst biopsy and the latter was delivered through a normal pregnancy without blastocyst biopsy. Each group consisted of 15 animals. We found no effects of blastocyst biopsy on reproductive capacities and weight gain. As for neurobehavioral evaluation between both groups, there were no significant differences in tail suspension test, sucrose preference test, the open field test and the elevated plus maze. Western blotting, immunohistochemistry and quantitative RT-PCR results showed that the expression levels of MBP, PRDX5 and UCHL1 in the PGD group were not significantly different compared to the control group, but SNAP-α expression in the PGD group was lower than that in control group. In summary, we concluded that blastocyst biopsy had no adverse effect on the general growth and behavior in mice. However, blastocyst biopsy effected the expression of SNAP-α. Therefore, the safety of blastocyst biopsy requires further evaluation.

CRISPR/Cas9-Mediated Biallelic Knockout of IRX3 Reduces the Production and Survival of Somatic Cell-Cloned Bama Minipigs

Bama minipigs are a local pig breed that is unique to China and has a high development and utilization value. However, its high fat content, low feed utilization rate, and slow growth rate have limited its popularity and utilization. Compared with the long breeding cycle and high cost of traditional genetic breeding of pigs, clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) endonuclease 9 system (CRISPR/Cas9)-mediated gene editing can cost-effectively implement targeted mutations in animal genomes, thereby providing a powerful tool for rapid improvement of the economic traits of Bama minipigs. The iroquois homeobox 3 (IRX3) gene has been implicated in human obesity. Mouse experiments have shown that knocking out IRX3 significantly enhances basal metabolism, reduces fat content, and controls body mass and composition. This study aimed to knock out IRX3 using the CRISPR/Cas9 gene editing method to breed Bama minipigs with significantly reduced fat content. First, the CRISPR/Cas9 gene editing method was used to efficiently obtain IRX3-/- cells. Then, the gene-edited cells were used as donor cells to produce surviving IRX3-/- Bama minipigs using somatic cell cloning. The results show that the use of IRX3-/- cells as donor cells for the production of somatic cell-cloned pigs results in a significant decrease in the average live litter size and a significant increase in the average number of stillbirths. Moreover, the birth weight of surviving IRX3-/- somatic cell-cloned pigs is significantly lower, and viability is poor such that all piglets die shortly after birth. Therefore, the preliminary results of this study suggest that IRX3 may have important biological functions in pigs, and IRX3 should not be used as a gene editing target to reduce fat content in Bama minipigs. Moreover, this study shows that knocking out IRX3 does not favor the survival of pigs, and whether targeted regulation of IRX3 in the treatment of human obesity will also induce severe adverse consequences requires further investigation.

Enhancement of in Vitro Developmental Outcome of Cloned Goat Embryos After Epigenetic Modulation of Somatic Cell-Inherited Nuclear Genome with Trichostatin A

In this study, the effect of trichostatin A (TSA)-mediated epigenomic modulation of nuclear donor cells on the in vitro developmental potential of caprine somatic cell cloned embryos was examined. The enucleated ex vivo-matured oocytes were subzonally injected with adult ear skin-derived fibroblast cells exposed or not exposed to TSA (at a concentration of 50 nM). The experiment was designed on the basis of three different approaches to TSA-dependent modulation of donor cell-descended genome: before being used for somatic cell nuclear transfer/SCNT (Group I); immediately after activation of nuclear-transferred (NT) oocytes (Group II); or combined treatment both before being used for SCNT and after activation of NT oocytes (Group III). In the control Group IV, donor cell nuclei have not been treated with TSA at any stage of the experimental design. In TSA-treated Groups I and II and untreated Group IV, cleavage activities of cloned embryos were at the similar levels (80.6%, 79.8% and 77.1%, respectively). But, significant difference was observed between Groups III and IV (85.3 vs. 77.1%). Moreover, in the experimental Groups I and III, the percentages of cloned embryos that reached the blastocyst stages remarkably increased as compared to those noticed in the control Group IV (31.2% vs. 36.7% vs. 18.9%, respectively). In turn, among embryos assigned to Group II, blastocyst formation rate was only slightly higher than that in the control Group IV, but the differences were not statistically significant (25.8% vs. 18.9%). To sum up, TSA-based epigenomic modulation of somatic cell-inherited nuclear genome gave rise to increased competences of caprine cloned embryos to complete their development to blastocyst stages. In particular, sequential TSA-mediated modulation of both nuclear donor cells and activated NT oocytes led to improvement in the blastocyst yields of cloned goat embryos, which can result from enhanced donor cell nuclear reprogrammability.

Stem cells and reproduction

Reproductive biotechnology has developed rapidly and is now able to overcome many birth difficulties due to infertility or the transmission of genetic diseases. Here we introduce the next generation of assisted reproductive technologies (ART), such as mitochondrial replacement technique (MRT) or genetic correction in eggs with micromanipulation. Further, we suggest that the transmission of genetic information from somatic cells to subsequent generations without gametes should be useful for people who suffer from infertility or genetic diseases. Pluripotent stem cells (PSCs) can be converted into germ cells such as sperm or oocytes in the laboratory. Notably, germ cells derived from nuclear transfer embryonic stem cells (NT-ESCs) or induced pluripotent stem cells (iPSCs) inherit the full parental genome. The most important issue in this technique is the generation of a haploid chromosome from diploid somatic cells. We hereby examine current science and limitations underpinning these important developments and provide recommendations for moving forward.

Production of cloned cats using additional complimentary cytoplasm

Somatic cell nuclear transfer (SCNT) is an important technique for producing cloned animals. It, however, is inefficient when there is use of SCNT for cloned animal production. Cytoplasm injection cloning technology (CICT) was developed to overcome the inefficiencies of SCNT use of this purpose. The use of CICT involves additional cytoplasm fusing with enucleated oocytes to restore the cytoplasmic volume, thus improving the in vitro developmental competence and quality of cloned embryos. In this study, there was application of CICT in cats to improve the in vitro developmental competence of cloned embryos, as well as the production of the offspring. The results of this study were that fusion rate of the cloned embryos with use of the CICT method was greater than that with SCNT (80.0 ± 4.8% compared with 67.8 ± 11.3%, respectively), and more blastocysts developed with use of CICT than SCNT (20.0 ± 2.0% compared with 13.5 ± 5.0%, respectively). The 62 cloned embryos that were produced with use of CICT were transferred into five estrous synchronized recipients, and 151 cloned embryos produced using SCNT were transferred to 13 estrous-synchronized recipients. After the embryo transfer, there was birth from surrogate mothers of one live-born kitten that resulted using SCNT compared with three live-born kittens using CICT. The number of CICT-cloned embryos born was greater than that of SCNT-cloned embryos (4.8 ± 2.3% compared with 0.7 ± 1.3%, P <  0.05). These results indicate that the CICT technique can be used to produce cloned kittens, including endangered feline species.

Expression of pluripotency-related genes is highly dependent on trichostatin A-assisted epigenomic modulation of porcine mesenchymal stem cells analysed for apoptosis and subsequently used for generating cloned embryos

The present study sought to examine whether trichostatin A (TSA)-assisted epigenetic transformation of porcine bone marrow (BM)-derived mesenchymal stem cells (BM-MSCs) affects the transcriptional activities of pluripotency-related genes (Oct4, Nanog, c-Myc, Sox2 and Rex1), multipotent stemness-related gene (Nestin) and anti-apoptotic/anti-senescence-related gene (Survivin). Epigenetically transformed or non-transformed BM-MSCs that had been transcriptionally profiled by qRT-PCR and had been analysed for different stages of apoptosis progression provided a source of nuclear donor cells for the in vitro production of cloned pig embryos. TSA-mediated epigenomic modulation has been found to enhance the multipotency extent, stemness and intracellular anti-ageing properties of porcine BM-MSCs. This has been confirmed by the relative abundances for Nanog, c-Myc Rex1, Sox2 and Survivin mRNAs in TSA-exposed BM-MSCs that turned out to be significantly higher than those of TSA-unexposed BM-MSCs. Additionally, TSA-assisted epigenomic modulation of BM-MSCs did not impact the caspase-8 activity, Bax protein expression and the incidence of TUNEL-positive cells. In conclusion, the considerably elevated quantitative profiles of Sox2, Rex1, c-Myc, Nanog and Survivin mRNA transcripts seem to trigger improved reprogrammability of TSA-treated BM-MSC nuclei in cloned pig embryos that thereby displayed remarkably increased blastocyst formation rates as compared to those noticed for embryos derived from TSA-untreated BM-MSCs.

Determining Influence of Culture Media and Dose-Dependent Supplementation with Basic Fibroblast Growth Factor on the Ex Vivo Proliferative Activity of Domestic Cat Dermal Fibroblasts in Terms of Their Suitability for Cell Banking and Somatic Cell Cloning of Felids

Dermal fibroblasts are commonly used as donors of genetic material for somatic cell nuclear transfer in mammals. Basic fibroblast growth factor (bFGF) is a cytokine that regulates proliferation and differentiation of different cell types. The study was aimed at optimizing the cell culture protocol for cat dermal fibroblasts by assessing the influence of culture media and different doses of bFGF on proliferation of fibroblasts and their viability in terms of cell banking and somatic cloning of felids. In Experiment I, skin biopsies of domestic cats were cultured in DMEM (D) and/or DMEM/F12 (F), both supplemented with 5 ng bFGF/ml (D-5, F-5, respectively). After the primary culture reached ~80% of confluency, the cells were passaged (3–4 times) and cultured in media with (D-5, F-5) or without (D-0, F-0) bFGF. To determine the optimal doses of bFGF, in Experiment II, secondary fibroblasts were cultured in DMEM with 0 (D-0), 2.5 (D-2.5), 5 (D-5) or 10 (D-10) ng bFGF/ml. The results showed that in D-5 the cells proliferated faster than in D-0, F-5 and F-0. Due to their poor proliferation, passages IV were not performed for cells cultured in F-0. In experiment II, a dose-dependent effect of bFGF on proliferation of cat dermal fibroblasts was found. In D-5 and D-10, the cells exhibited higher (P<0.05) proliferation compared with D-0. In D-2.5 the cells showed a tendency to proliferate slower than in D-5 and D-10 and at the same faster than in D-0. In conclusion. DMEM supplemented with bFGF provides better proliferation of domestic cat dermal fibroblasts culture than DMEM/F12. Supplementation of culture medium with bFGF has a beneficial effect on cat dermal fibroblast proliferation and could be recommended for addition to culture media.

Identifying Biomarkers of Autophagy and Apoptosis in Transfected Nuclear Donor Cells and Transgenic Cloned Pig Embryos

In this study, we first investigated the effects of 3-methyladenine (3-MA), an autophagy inhibitor, and the inducer – rapamycin (RAPA) on the incidence of programmed cell death (PCD) symptoms during in vitro development of porcine somatic cell nuclear transfer (SCNT)-derived embryos. The expression of autophagy inhibitor mTOR protein was decreased in porcine SCNT blastocysts treated with 3MA. The abundance of the autophagy marker LC3 increased in blastocysts following RAPA treatment. Exposure of porcine SCNT-derived embryos to 3-MA suppressed their developmental abilities to reach the blastocyst stage. No significant difference in the expression pattern of PCD-related proteins was found between non-transfected dermal cell and transfected dermal cell groups. Additionally, the pattern of PCD in SCNT-derived blastocysts generated using SC and TSC was not significantly different, and in terms of porcine SCNT-derived embryo development rates and total blastocyst cell numbers, there was no significant difference between non-transfected cells and transfected cells. In conclusion, regulation of autophagy affected the development of porcine SCNT embryos. Regardless of the type of nuclear donor cells (transfected or non-transfected dermal cells) used for SCNT, there was no difference in the developmental potential and quantitative profiles of autophagy/apoptosis biomarkers between porcine transgenic and non-transgenic cloned embryos. These results led us to conclude that PCD is important for controlling porcine SCNT-derived embryo development, and that transfected dermal cells can be utilized as a source of nuclear donors for the production of transgenic cloned progeny in pigs.