Treatment of Donor Cells and Reconstructed Embryos with a Combination of Trichostatin-A and 5-aza-2'-Deoxycytidine Improves the Developmental Competence and Quality of Buffalo Embryos Produced by Handmade Cloning and Alters Their Epigenetic Status and Gene Expression

Effects of epigenetic modifier on the developmental competence and quantitative expression of genes in male and female buffalo (Bubalus bubalis) cloned embryos

Adult male and female Murrah buffalo fibroblast cells were used as donors for the production of embryos using handmade cloning. Both donor cells and reconstructed embryos were treated with 50 nM trichostatin-A (TSA) and 7.5 nM 5-aza-2'-deoxycytidine (5-aza-dC). The blastocyst rate of both treated male (40.1% ± 2.05) and female (37.0% ± 0.83) embryos was significantly lower than in untreated control males (49.7% ± 3.80) and females (47.2% ± 2.44) but their apoptotic index was lower (male, control: 5.90 ± 0.48; treated: 4.96 ± 0.31): (female, control: 8.11 ± 0.67; treated: 6.65 ± 0.43) and epigenetic status in terms of global acetylation and methylation of histone was significantly improved. The expression level of hypoxanthine-guanine phosphoribosyltransferase (HPRT) was higher (P < 0.05) and that of PGK, G6PD, OCT 4, IFN-tau and CASPASE3 was significantly lower (P < 0.05) in treated male blastocyst than control and the expression levels of DNMT1, IGF1R and BCL-XL were not significantly different between the two groups. In the female embryos, the relative mRNA abundance of OCT4 was significantly higher (P < 0.05), and that of XIST and CASPASE3 was significantly lower (P < 0.05) in the epigenetic modifier-treated group compared with that of the control group, whereas the expression levels of HPRT, PGK, G6PD, DNMT1, IFN-tau, IGF1R and BCL-XL were not significantly different between the two groups. In both embryos, a similar effect of treatment was observed on genes related to growth and development, but the effect on the expression of X-linked genes varied. These results indicate that not all X-linked genes respond to TSA and 5-aza-dC treatment in the same manner.

Production of Water Buffalo SCNT Embryos by Handmade Cloning

Cloning by somatic cell nuclear transfer (SCNT) involves the transfer of a somatic nucleus into an enucleated oocyte followed by chemical activation and embryo culture. Further, handmade cloning (HMC) is a simple and efficient SCNT method for large-scale embryo production. HMC does not require micromanipulators for oocyte enucleation and reconstruction since these steps are carried out using a sharp blade controlled by hand under a stereomicroscope. In this chapter, we review the status of HMC in the water buffalo (Bubalus bubalis) and further describe a protocol for the production of buffalo-cloned embryos by HMC and assays to estimate their quality.

Current status of assisted reproductive technologies in buffaloes

Buffaloes are raised by small farm holders primarily as source of draft power owing to its resistance to hot climate, disease, and stress conditions. Over the years, transformation of these animals from draft to dairy was deliberately carried out through genetic improvement program leading to the development of buffalo-based enterprises. Buffalo production is now getting more attention and interest from buffalo raisers due to its socioeconomic impact as well as its contribution to propelling the livestock industry in many developing countries. Reproduction of buffaloes, however, is confronted with huge challenge and concern as being generally less efficient to reproduce compared with cattle due to both intrinsic and extrinsic factors such as poor estrus manifestation, silent heat, marked seasonal infertility, postpartum anestrus, long calving interval, delayed puberty, inherently low number of primordial follicles in their ovaries, high incidence of atresia, and apoptosis. Assisted reproductive technologies (ARTs) are major interventions for the efficient utilization of follicle reserve in buffaloes. The present review focuses on estrus and ovulation synchronization for fixed time artificial insemination, in vitro embryo production, intracytoplasmic sperm injection, cryopreservation of oocytes and embryos, somatic cell nuclear transfer, the factors affecting utilization in various ARTs, and future perspectives in buffaloes.

Trichostatin A-Assisted Epigenomic Modulation Affects the Expression Profiles of Not Only Recombinant Human α1,2-Fucosyltransferase and α-Galactosidase A Enzymes But Also Galα1→3Gal Epitopes in Porcine Bi-Transgenic Adult Cutaneous Fibroblast Cells

This study was conducted to explore whether trichostatin A-assisted epigenomic modulation (TSA-EM) can affect the expression of not only recombinant human α1,2-fucosyltransferase (rhα1,2-FT) and α-galactosidase A (rhα-Gal A) immune system enzymes but also Galα1→3Gal epitopes in ex vivo proliferating adult cutaneous fibroblast cells (ACFCs) derived from hFUT2×hGLA bi-transgenic pigs that had been produced for the needs of future xenotransplantation efforts. The ACFC lines were treated with 50 nM TSA for 24 h and then the expression profiles of rhα1,2-FT and rhα-Gal A enzymes were analyzed by Western blot and immunofluorescence. The expression profiles of the Galα1→3Gal epitope were determined by lectin blotting and lectin fluorescence. The ACFCs derived from non-transgenic (nTG) pigs were served as the negative (TSA-) and positive (TSA+) control groups. For both hFUT2×hGLA and nTG samples, the expression levels of α1,2-FT and α-Gal A proteins in TSA+ cells were more than twofold higher in comparison to TSA- cells. Moreover, a much lower expression of the Galα1→3Gal epitopes was shown in TSA- hFUT2×hGLA cells as compared to the TSA- nTG group. Interestingly, the levels of Galα1→3Gal expression in TSA-treated hFUT2×hGLA and nTG ACFCs were significantly higher than those noticed for their TSA-untreated counterparts. Summing up, ex vivo protection of effectively selected bi-transgenic ACFC lines, in which TSA-dependent epigenetic transformation triggered the enhancements in reprogrammability and subsequent expression of hFUT2 and hGLA transgenes and their corresponding transcripts, allows for cryopreservation of nuclear donor cells, nuclear-transferred female gametes, and resultant porcine cloned embryos. The latter can be used as a cryogenically conserved genetic resource of biological materials suitable for generation of bi-transgenic cloned offspring in pigs that is targeted at biomedical research in the field of cell/tissue xenotransplantation.

Manipulating the Epigenome in Nuclear Transfer Cloning: Where, When and How

The nucleus of a differentiated cell can be reprogrammed to a totipotent state by exposure to the cytoplasm of an enucleated oocyte, and the reconstructed nuclear transfer embryo can give rise to an entire organism. Somatic cell nuclear transfer (SCNT) has important implications in animal biotechnology and provides a unique model for studying epigenetic barriers to successful nuclear reprogramming and for testing novel concepts to overcome them. While initial strategies aimed at modulating the global DNA methylation level and states of various histone protein modifications, recent studies use evidence-based approaches to influence specific epigenetic mechanisms in a targeted manner. In this review, we describe-based on the growing number of reports published during recent decades-in detail where, when, and how manipulations of the epigenome of donor cells and reconstructed SCNT embryos can be performed to optimize the process of molecular reprogramming and the outcome of nuclear transfer cloning.

Effects of 5-Aza-2'-deoxycytidine on hormone secretion and epigenetic regulation in sika deer ovarian granulosa cells

5-Aza-2'-deoxycytidine (5-Aza-dC), an inhibitor of DNA methyltransferases, is an effective treatment for various cancers and has improved the development rate of cloned embryos. Previous studies have reported the effect of 5-Aza-dC on fibroblasts; however, the mechanism whereby 5-Aza-dC affects sika deer granulosa cells and hormone secretion is presently unknown. Here, we showed that the cell cycle after treatment with different doses of 5-Aza-dC was significantly altered. The number of cells in the S phase was significantly increased in response to a concentration of 0.1 μM 5-Aza-dC. The rate of apoptosis was increased when cells were treated with 0.1 μM and 5 μM 5-Aza-dC. We showed that the protein level of H3K9me2 was significantly decreased in response to 5-Aza-dC. The activity levels of DNA methyltransferase were reduced by a moderate dose of 5-Aza-dC. Furthermore, the secretion of E₂ and P₄ was influenced by different doses of 5-Aza-dC. Our study suggested that 5-Aza-dC affected hormone secretion in sika deer granulosa cells through cell development and epigenetic regulation. The findings of this study lay the foundation for further epigenetic studies in sika deer.

Targeting epigenetic nuclear reprogramming in aggregated cloned equine embryos

Epigenetic perturbations during the reprogramming process have been described as the primary cause of the low efficiency of somatic cell nuclear transfer (SCNT). In this study, we tested three strategies targeting nuclear reprogramming to investigate effects on equine SCNT. First, we evaluated the effect of treating somatic cells with chetomin, a fungal secondary metabolite reported to inhibit the trimethylation on histone 3 lysine 9 (H3K9 me3). Second, caffeine was added to the culture medium during the enucleation of oocytes and before activation of reconstructed embryos as a protein phosphatase inhibitor to improve nuclear reprogramming. Third, we tested the effects of the histone deacetylase inhibitor trichostatin A (TSA) added during both activation and early embryo culture. Although none of these treatments significantly improved the developmental rates of the invitro aggregated cloned equine embryos, the first equine cloned foal born in Australia was produced with somatic cells treated with chetomin. The present study describes the use of chetomin, caffeine and TSA for the first time in horses, serving as a starting point for the establishment of future protocols to target epigenetic reprogramming for improving the efficiency of equine cloning. Cloning is an expensive and inefficient process, but has gained particular interest in the equine industry. In this study we explored different strategies to improve cloning efficiency and produced the first cloned foal born in Australia. Our data serve as a starting point for the establishment of future protocols for improving equine cloning efficiency.

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.

Approaches used to improve epigenetic reprogramming in buffalo cloned embryos

The reproductive cloning in buffalo in India has been started using a simplified somatic cell nuclear transfer technique named handmade cloning. Since the birth of first cloned female buffalo in 2009, a number of buffalo clones have been produced in India by utilizing different types of donor cells such as ear cells, embryonic stem cells, semen somatic cells and urine somatic cells. The use of buffalo cloning on a large scale is restricted due to low pregnancy rates and poor calf survival. Considerable attempts have been made to improve the overall buffalo cloning efficiency, particularly by modifying epigenetic reprogramming of cloned embryos. Previous studies have demonstrated that chemical epigenetic modifiers such as trichostatin A and 5-aza-2’-deoxycytidine, m-carboxycinnamic acid bishydroxamide can be used to treat donor somatic cells and reconstructed fused embryos to correct the epigenetic reprogramming to enhance the overall cloning efficiency in terms of live birth rates.

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.

Functions of intrinsic disorder in proteins involved in DNA demethylation during pre-implantation embryonic development

DNA demethylation is involved in many biological processes during pre-implantation embryonic development in mammals. To date, the complicated mechanism of DNA demethylation is still not fully understood. Ten-eleven translocation family (TET3, TET1 and TET2), thymine DNA glycosylase (TDG) and DNA methyltransferase 1 (DNMT1) are considered the major protein enzymes of DNA demethylation in pre-implantation embryos. TET3, TET1, TET2, TDG, and DNMT1 contain abundant levels of intrinsically disordered protein regions (IDPRs), which contribute to increasing the functional diversity of proteins. Thus we tried to explore the complicated DNA demethylation in pre-implantation embryos from the intrinsic disorder perspective. These five biological macromolecules all have DNA demethylation-related functional domains. They can work together to fulfill DNA demethylation in pre-implantation embryos through complex protein-protein interaction networks. Intrinsic disorder analysis results showed these proteins were partial intrinsically disordered proteins. Many identifiable disorder-based DNA-binding sites, protein-binding sites and post-translational modification sites located in the intrinsically disordered regions, and DNA demethylation deficiency point mutations in the IDPRs could significantly change the local disorder propensity of these proteins. To the best of our knowledge, this work provides a new viewpoint for studying the mechanism of DNA methylation reprogramming during mammalian pre-implantation embryonic development.

Cloning: A Sleeping Beauty Awaiting the Kiss?

The first 20 years of somatic cell nuclear transfer can hardly be described as a success story. Controversially, many factors leading to the fiasco are not intrinsic features of the technique itself. Misunderstandings and baseless accusations alongside with unsupported fears and administrative barriers hampered cloners to overcome the initial challenging period with obvious difficulties that are common features of a radically new approach. In spite of some promising results of mostly sporadic and small-scale experiments, the future of cloning is still uncertain. On the other hand, a reincarnation, just like the idea of electric cars, may result in many benefits in various areas of science and economy. One can only hope that-in contrast to electric cars-the ongoing paralyzed phase will not last for 100 years, and breakthroughs achieved in some promising areas will provide enough evidence to intensify research and large-scale application of cloning in the next decade.

Cloning of breeding buffalo bulls in India: Initiatives & challenges

The term animal cloning refers to an asexual mean of reproduction to produce genetically identical copies of any animal without the use of sperm. In India, the cloning of buffalo is well established and clones of the Murrah, the best dairy breed of buffalo, have been produced. The most acclaimed example is the restoration of progeny-tested breeding bull by isolating somatic cells from frozen doses of semen, which were stored for more than a decade in the semen bank. Buffalo bull cloning is considered the best available option to reproduce declared proven bulls and their semen would contribute to accomplishing the demand of ever-growing frozen semen, which is the prime requirement of conventional breeding. This article highlights the importance of buffalo bull cloning and its current status in India.

Use of trichostatin A alters the expression of HDAC3 and KAT2 and improves in vitro development of bovine embryos cloned using less methylated mesenchymal stem cells

The aim of this work was to investigate the methylation and hydroxymethylation status of mesenchymal stem cells (MSC) from amniotic fluid (MSC-AF), adipose tissue (MSC-AT) and fibroblasts (FIB-control) and to verify the effect of trichostatin A (TSA) on gene expression and development of cloned bovine embryos produced using these cells. Characterization of MSC from two animals (BOV1 and BOV2) was performed by flow cytometry, immunophenotyping and analysis of cellular differentiation genes expression. The cells were used in the nuclear transfer in the absence or presence of 50 nM TSA for 20 hr in embryo culture. Expression of HDAC1, HDAC3 and KAT2A genes was measured in embryos by qRT-PCR. Methylation results showed difference between animals, with MSC from BOV2 demonstrating lower methylation rate than BOV1. Meanwhile, MSC-AF were less hydroxymethylated for both animals. MSC-AF from BOV2 produced 44.92 ± 8.88% of blastocysts when embryos were exposed to TSA and similar to embryo rate of MSC-AT also treated with TSA (37.96 ± 15.80%). However, when methylation was lower in FIB compared to MSC, as found in BOV1, the use of TSA was not sufficient to increase embryo production. MSC-AF embryos expressed less HDAC3 when treated with TSA, and expression of KAT2A was higher in embryos produced with all MSC and treated with TSA than embryos produced with FIB. The use of MSC less methylated and more hydroxymethylated in combination with embryo incubation with TSA can induce lower expression of HDAC3 and higher expression of KAT2A in the embryos and consequently improve bovine embryo production.

An update: Reproductive handmade cloning of water buffalo (Bubalus bubalis)

The first birth of a cloned animal produced through the Handmade cloning (HMC) technique was reported more than 15 years ago in cattle. This method of somatic cell nuclear transfer (SCNT) has subsequently been evolving as a much simpler alternative to the classical micromanipulator-based SCNT. Several farm animal species such as cattle, buffalo, pigs, sheep, and goats have been successfully cloned using HMC. In buffalo, HMC technique is now well established, and several births of cloned calves have been reported by us. Several factors such as source of somatic cells, quality of recipient oocytes, cell cycle stage prior to SCNT, electrofusion and culture conditions, and epigenetic status of somatic cells, have been optimized leading to the production of good quality cloned embryos. The preservation through cloning of proven breeding bulls that have died by producing live offspring using somatic cells isolated from frozen semen as donor cells and birth of a cloned calf from urine-derived cells are impressive examples of the success of HMC in buffalo. In conclusion, HMC is a valued reproductive technique in buffalo that offers the opportunity to make multiple copies of highly valuable animals, particularly proven breeding bulls. In this review, there is a discussion of the advancement of the HMC technique in buffalo and factors responsible for the efficient production of cloned embryos.

VPA selectively regulates pluripotency gene expression on donor cell and improve SCNT embryo development

SCNT technology has been successfully used to clone a variety of mammals, but the cloning efficiency is very low. This low efficiency is likely due to the incomplete reprogramming of SCNT embryos. Histone modification and DNA methylation may participate in these events. Thus, it would be interesting to attempt to improve the efficiency of SCNT by using a HDACi VPA. In order to guarantee the effect of VPA and reduce its cytotoxicity, a comprehensive analysis of the cell proliferation and histone modification was performed. The results showed that 0.5 and 1 mM VPA treatment for 24 h were the optimal condition. According to the results, H3K4me3 was increased in 0.5 and 1 mM VPA groups, whereas H3K9me2 was significantly decreased. These are the signals of gene-activation. In addition, VPA treatment led to the overexpression of Oct4 and Nanog. These indicated that VPA-treated cells had similar patterns of histone to zygotic embryos, and may be more favorable for reprograming. A total of 833 cloned embryos were produced from the experimental replicates of VPA-treated donor cells. In 1 mM treatment group, the blastocyst rates were significantly increased compared with control. At the same time, our findings demonstrated the interrelation between DNA methylation and histone modifications.