Factors affecting the development of somatic cell nuclear transfer embryos in Cattle

SIRT6 Knockdown in Buffalo Fetal Fibroblasts Exacerbates Premature Senescence Caused by DNA and Telomere Damage

As a gene with antiaging functions, sirtuin6 (SIRT6) belonging to the sirtuin family plays a vital role in DNA repair, telomerase function, and cellular senescence, as well as maintains epigenomic stability and promotes longevity. However, its role in cell senescence in large animals, such as buffaloes, remains unknown. Fibroblasts are commonly used for somatic reprogramming, and their physiological characteristics affect the efficiency of this process. We aimed to elucidate the role of SIRT6 in cellular senescence and proliferation and analyze its effect on the biological function of buffalo fibroblasts to help improve the efficiency of buffalo somatic cell reprogramming. The expression of SIRT6 and related DNA damage was measured in buffalo fibroblasts obtained at different developmental stages (in the fetus and at 3 and 10 years of age), and the effect of SIRT6 knockdown on the senescence of buffalo fetal fibroblast was investigated. An inverse relationship was observed between SIRT6 expression and senescence in buffalo fibroblasts obtained from animals of various ages. This was accompanied by decreased cell growth, viability, and increased DNA damage. Short hairpin RNA-mediated SIRT6 knockdown accelerated the senescence of buffalo fetal fibroblasts. It blocked the cell cycle during in vitro cell culture, which further enhanced DNA damage, particularly with respect to the telomeres. Collectively, our findings suggest that SIRT6 expression was closely associated with buffalo senescence in fibroblasts. These findings serve as a foundation to better understand the cellular functions of SIRT6 and also aid in selecting donor cells for buffalo somatic cell reprogramming.

Cloning in action: can embryo splitting, induced pluripotency and somatic cell nuclear transfer contribute to endangered species conservation?

The term 'cloning' refers to the production of genetically identical individuals but has meant different things throughout the history of science: a natural means of reproduction in bacteria, a routine procedure in horticulture, and an ever-evolving gamut of molecular technologies in vertebrates. Mammalian cloning can be achieved through embryo splitting, somatic cell nuclear transfer, and most recently, by the use of induced pluripotent stem cells. Several emerging biotechnologies also facilitate the propagation of genomes from one generation to the next whilst bypassing the conventional reproductive processes. In this review, we examine the state of the art of available cloning technologies and their progress in species other than humans and rodent models, in order to provide a critical overview of their readiness and relevance for application in endangered animal conservation.

Molecular Mechanism and Application of Somatic Cell Cloning in Mammals-Past, Present and Future

Thus far, nearly 25 mammalian species have been cloned by intra- or interspecies somatic cell nuclear transfer (SCNT) [...].

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

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

Effects of Donor Cell Types on the Development of Bovine Embryos Using Cytoplasm Injection Cloning Technology

Cytoplasm injection cloning technology (CICT) is an efficient technique for evaluating the developmental potential of cloned embryos. In this study, we investigated the effects of donor cell type on the developmental potential and quality of cloned bovine embryos. Adult fibroblasts (AFs) and embryonic cells (ECs) were used as donor cells to clone bovine embryos using CICT. We initially used AF cells to develop cloned embryos and then cultured the cloned day-8 blastocysts for 10 days to obtain ECs as donor cells for second embryo cloning. We found that the bovine blastocysts cloned using AF cells had significantly reduced developmental rates, embryo quality, and ratios of inner cell mass (ICM) to the total number of cells compared to those using ECs as donor cells. Furthermore, there were significant differences in the DNA methyltransferase-, histone deacetylation-, apoptosis-, and development-related genes at the blastocyst stage in embryos cloned from AFs compared to those in embryos cloned from ECs. Our results suggest that using ECs as donor cells for nuclear transfer enhances the quantity and quality of cloned embryos. However, further investigation is required in terms of determining pregnancy rates and developing cloned embryos from different donor cell types.

Animal cloning and consumption of its by-products: A scientific and Islamic perspectives

Islam is a religion that inspires its followers to seek knowledge continually and nurtures innovation, within the realms of Islamic rulings, towards an ameliorated quality of life. Up-to-date biotechnological techniques, specifically animal cloning, are involved in advancing society's health, social, and economic domains. The goal of animal cloning includes the production of genetically modified animal for human consumption. Therefore, this research endeavoured to study animal cloning's current scientific findings, examine the by-product of said process, and determine its permissibility in an Islamic context. This study employed descriptive literature reviews. Results concluded that animal cloning, especially in mammals, does not occur naturally as in plants. A broadly trusted and efficient animal cloning method is known as Somatic Cell Nuclear Transfer (SCNT), which includes three principal steps: oocyte enucleation; implantation of donor cells (or nucleus); and the activation of the embryo. Nevertheless, the limitations of SCNT, particularly to the Large Offspring Syndrome (LOS), should be noted. One of the forms of the application of animal cloning is in agriculture. From an Islamic perspective, determining the permissibility of consuming cloned animals as food is essentially based on whether the cloned animal conforms to Islamic law's principles and criteria. Islam interdicts animal cloning when it is executed without benefiting humans, religion, or society. Nonetheless, if it is done to preserve the livelihood and the needs of a community, then the process is deemed necessary and should be administered following the conditions outlined in Islam. Hence, the Islamic ruling for animal cloning is not rigid and varies proportionately with the current fatwa.

Efficient One-Step Knockout by Electroporation of Ribonucleoproteins Into Zona-Intact Bovine Embryos

Somatic cell nuclear transfer or cytoplasm microinjection have been used to generate genome-edited farm animals; however, these methods have several drawbacks that reduce their efficiency. This study aimed to develop electroporation conditions that allow delivery of CRISPR/Cas9 system to bovine zygotes for efficient gene knock-out. We optimized electroporation conditions to deliver Cas9:sgRNA ribonucleoproteins to bovine zygotes without compromising embryo development. Higher electroporation pulse voltage resulted in increased membrane permeability; however, voltages above 15 V/mm decreased embryo developmental potential. The zona pellucida of bovine embryos was not a barrier to efficient RNP electroporation. Using parameters optimized for maximal membrane permeability while maintaining developmental competence we achieved high rates of gene editing when targeting bovine OCT4, which resulted in absence of OCT4 protein in 100% of the evaluated embryos and the expected arrest of embryonic development at the morula stage. In conclusion, Cas9:sgRNA ribonucleoproteins can be delivered efficiently by electroporation to zona-intact bovine zygotes, resulting in efficient gene knockouts.

CRISPR/Cas12a mediated knock-in of the Polled Celtic variant to produce a polled genotype in dairy cattle

In modern livestock farming horned cattle pose an increased risk of injury for each other as well as for the farmers. Dehorning without anesthesia is associated with stress and pain for the calves and raises concerns regarding animal welfare. Naturally occurring structural variants causing polledness are known for most beef cattle but are rare within the dairy cattle population. The most common structural variant in beef cattle consists of a 202 base pair insertion-deletion (Polled Celtic variant). For the generation of polled offspring from a horned Holstein-Friesian bull, we isolated the Polled Celtic variant from the genome of an Angus cow and integrated it into the genome of fibroblasts taken from the horned bull using the CRISPR/Cas12a system (formerly Cpf1). Modified fibroblasts served as donor cells for somatic cell nuclear transfer and reconstructed embryos were transferred into synchronized recipients. One resulting pregnancy was terminated on day 90 of gestation for the examination of the fetus. Macroscopic and histological analyses proved a polled phenotype. The remaining pregnancy was carried to term and delivered one calf with a polled phenotype which died shortly after birth. In conclusion, we successfully demonstrated the practical application of CRISPR/Cas12a in farm animal breeding and husbandry.

The in vitro development of cloned sheep embryos treated with Scriptaid and Trichostatin (A)

Although, it has been success in the generation of animal clones from somatic cells in various animal species, the information related to nuclear reprogramming of cloned embryos is found to be limited. This study aims to compares the effect of both Scriptaid (SCR) and Trichostatin (A) treatments in improving cloning efficiency, and embryos developmental rate of cloned sheep embryos in vitro. Three groups were formed, i.e., one SCR group, second TSA group, with both treatment concentrations of 5 nM, 50 nM, and 500 nM, respectively, and third were control group with 0 nM. Methods: Ovaries of slaughtered sheep were collected and oocytes were recovered from antral follicles using aspiration method and in vitro maturation of oocytes were done. Then zona dissecting with micropipettes and oocyte enucleation were carried out under the micromanipulator. Later nuclear transfer, cell fusion and activation were done via cell fusion machine. Finally the embryo cultured in incubating chamber at the CO2 incubator up to 9 days. The result: In general the results showed that when the concentration increases the cleavage rate increased. The cleavage rates of the SCNT embryos treated with SCR at different concentrations are closely related to cleavage rate of embryos treated with TSA at same concentration; such as 39.47% for 500 nM TSA, 38.09% for 500 nM SCR; 18.6% for 50 nM TSA, 19.17% for 50 nM SCR, and 22.64% for 5 nM TSA, 17.18% for 5 nM SCR. As for the control group, the cleavage rate of the SCNT embryos cleavage ratewere27.47%., 30% and 30.85% respectively for bothtreatments. While there is a significant difference in TSA treatments at an eight-cell stage at the concentration (5 and 50 nM TSA) compared to the all other cleavage cell stages of (500 nM TSA and control). Also their were a differences between (50 nM of TSA) compared to the (50 nM SCR). Also there were a significant differences between the 16 cell stage at the (500 nM TSA) compared to other treatment (5 nM, 50 nM TSA and control). Regarding the SCR there were a significant difference at 8 cell stage between (5 nM SCR), compared to the other treatment (50 nM, 500 nM SCR and control). Also there were a significant difference at 16 cell stage between (50 nM, and 500 nM SCR), compared to the other treatment (5 nM SCR and control). While in the development of the embryos reach to blastocyst stage the SCR and the control group show a higher rate, in compered to TSA that did not show any development to blastocyst stage. The total SCR treatment showed (3/41 = 7.31%), and the total control showed (4/89 = 4.49%) blastula stage. It concludes that SCR improve the final development blastula stage compared to the TSA treatments that did not improved embryos reach to final developmental blastula stages may be due to spices differences or to the toxicity of TSA, especially at higher concentrations.

Whole-Genome Methylation Analysis Reveals Epigenetic Variation in Cloned and Donor Pigs

Somatic cloning has had a significant impact on the life sciences and is important in a variety of processes, including medical research and animal production. However, the application of somatic cloning has been limited due to its low success rate. Therefore, potential epigenetic variations between cloned and donor animals are still unclear. DNA methylation, one of the factors which is responsible for phenotypic differences in animals, is a commonly researched topic in epigenetic studies of mammals. To investigate the epigenetic variations between cloned and donor animals, we selected blood and ear fibroblasts of a donor pig and a cloned pig to perform whole-genome bisulfite sequencing (WGBS). A total of 215 and 707 differential methylation genes (DMGs) were identified in blood and ear fibroblasts, respectively. Functional annotation revealed that DMGs are enriched in many pathways, including T/B or natural killer (NK) cell differentiation, oocyte maturation, embryonic development, and reproductive hormone secretion. Moreover, 22 DMGs in the blood and 75 in the ear were associated with immune responses (e.g., CD244, CDK6, CD5, CD2, CD83, and CDC7). We also found that 18 DMGs in blood and 53 in ear fibroblasts were involved in reproduction. Understanding the expression patterns of DMGs, especially in relation to immune responses and reproduction, will reveal insights that will aid the advancement of future somatic cloning techniques in swine.

Genome editing approaches to augment livestock breeding programs

The prospect of genome editing offers a number of promising opportunities for livestock breeders. Firstly, these tools can be used in functional genomics to elucidate gene function, and identify causal variants underlying monogenic traits. Secondly, they can be used to precisely introduce useful genetic variation into structured livestock breeding programs. Such variation may include repair of genetic defects, the inactivation of undesired genes, and the moving of useful alleles and haplotypes between breeds in the absence of linkage drag. Editing could also be used to accelerate the rate of genetic progress by enabling the replacement of the germ cell lineage of commercial breeding animals with cells derived from genetically elite lines. In the future, editing may also provide a useful complement to evolving approaches to decrease the length of the generation interval through in vitro generation of gametes. For editing to be adopted, it will need to seamlessly integrate with livestock breeding schemes. This will likely involve introducing edits into multiple elite animals to avoid genetic bottlenecks. It will also require editing of different breeds and lines to maintain genetic diversity, and enable structured cross-breeding. This requirement is at odds with the process-based trigger and event-based regulatory approach that has been proposed for the products of genome editing by several countries. In the absence of regulatory harmony, researchers in some countries will have the ability to use genome editing in food animals, while others will not, resulting in disparate access to these tools, and ultimately the potential for global trade disruptions.

Developmental dynamics of cloned Mexican bighorn sheep embryos using morphological quality standards

The developmental dynamics of cloned Mexican bighorn sheep (Ovis canadensis mexicana) embryos were evaluated based on morphological quality standards. Categories determined by standards were correlated with the embryonic development stage, number of nuclei and viability. The results showed no differences in the blastocyst rate between the experimental (cloned Mexican bighorn sheep embryos) and control (parthenogenetic domestic sheep embryos) groups (p > .05), while type IV fragmentation was higher in clones (p < .05). The standards allowed for the identification of embryos that divided at least once or fragmented after 24 hr of culture. The highest percentage of morulae appeared at 96 hr, the final stages of development: nonsegmented, blocked, fragmented and blastocysts appeared at 192 hr. Embryonic quality decreased over time, making 96 hr the ideal time point to predict the final morphological quality of embryos. Nuclear staining of the morulae and blastocysts showed that higher embryo quality was associated with a higher percentage of normal and viable blastomeres. The evaluated criteria allowed for descriptions of the dynamics, stage and quality of cloned Mexican bighorn sheep embryos with a high degree of reliability. In addition, developmental anomalies, including fragmentation, multinucleation and blocking, were identified.

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.

High Pregnancy and Calving Rates with a Limited Number of Transferred Handmade Cloned Bovine Embryos

A major obstacle of widespread commercial application of bovine somatic cell nuclear transfer is the low overall efficiency, that is, healthy calf-late pregnancy per transferred embryo rate. In this study, we report a series of experiments with a limited number of embryos created with handmade cloning (HMC) and transferred without or after open pulled straw vitrification. Embryo reconstruction was performed by using in vitro matured oocytes and adult ear skin fibroblasts. In two experiments, a total of 53 D7 blastocysts were developed from 188 reconstructed embryos. Fresh transfer of seven blastocysts into six recipients has resulted in three early pregnancies, two of them developed over 90 days and eventually resulted in healthy calves (33% offspring/transfer rate). In another two experiments, a total of 11 D7 blastocysts were obtained from 36 reconstructed embryos. Out of these, eight have reexpanded 18 hours after vitrification and warming. Transfer of these blastocysts into eight recipients has resulted in four early pregnancies and two live births; 25% offspring/transfer rate. These results indicate that low overall efficiency may not be an intrinsic feature of cattle cloning, and selection of the right procedures may help to overcome the actual limitations.

PRIMARY FIBROBLAST CELL CYCLE SYNCHRONIZATION AND EFFECTS ON HANDMADE CLONED (HMC) BOVINE EMBRYOS

Abstract Spatial and temporal synchrony and compatibility between the receptor oocyte and the donor cell nucleus are necessary for the process of embryo cloning to allow nuclear reprogramming and early embryonic development. The objective of the present study was to evaluate three cell cycle synchronization methods on a primary bovine fibroblast culture for 24, 48, or 72 h. These fibroblasts were used as nuclear donors to evaluate their in vitro developmental potential and the quality of the embryos produced through handmade cloning (HMC). No differences were found between the methods used for fibroblast synchronization in G0/G1 (p > 0.05). Production of clones from fibroblasts in four groups- no treatment at 0 h and using serum restriction SR, high culture confluence HCC, and SR+HCC at 24 h- resulted in high cleavage rates that were not different. Embryo production rates were 37.9%, 29.5%, and 30.9% in the 0h, SR24h, and SR+HHC24h groups, respectively, and 19.3% in the HCC group, which was significantly different from the other three (p < 0.05). There were no differences in the quality parameter among the clones produced with fibroblasts subjected to the different synchronization. Finally, when overall clone production was compared versus parthenotes and IVF embryos, the only difference was between clones and parthenogenetic embryos with zona pellucida (30.2% vs 38.6%). The number of blastomeres from the blastocytes produced through IVF was significantly greater than those from embryos activated parthenogenetically and from clones (117, 80, 75.9, and 67.1, respectively). The evaluation of three synchronization methods at different time points did not demonstrate an increase in the percentage of fibroblasts in the G0/G1 phases of the cell cycle; however, good quality and high cloning rates were obtained, suggesting that it is not always necessary to subject the cells to any synchronization treatments, as they would yield equally good cloning results.

Dynamic changes in chromatin and microtubules at the first cell cycle in SCNT or IVF goat embryos

We investigated the dynamic changes in chromatin and microtubules at the first cell cycle in goat somatic cell nuclear transfer (SCNT)-derived and in vitro fertilization (IVF)-derived embryos. Stage-dependent and characteristic changes to chromatin and microtubules occurred in SCNT-derived embryos at different times after activation. About half donor nuclei underwent premature chromosome condensation (PCC) at 1 h post activation, and furtherly reached telophase at 2 h after activation. However, we discovered that the separated chromosomes reaggregated, not keeping two independent nuclei; and formed one pronucleus at 2.5 h after activation. One pronucleus was found in all reconstructed oocytes except other no nucleus oocytes from 3 to 22 h after activation. Reconstructed oocytes reached the first mitotic metaphase at 23 h post activation, which was later than that of IVF-derived embryos at 16 h after insemination. SCNT-derived embryos showed significantly higher abnormalities in the first mitotic metaphase spindle, compared with IVF-derived embryos. Abnormal spindles included multi polar and half spindles. SCNT-derived embryos began to cleave at 24 h after activation, which was later than that of IVF-derived embryos at 21 h after insemination. SCNT-derived embryos showed delayed conversion from telophase to interphase than IVF-derived embryos during cleavage. These might lead to poor development in SCNT-derived 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.

Determination of Oocyte-Manipulation, Zygote-Manipulation, and Genome-Reprogramming Effects on the Transcriptomes of Bovine Blastocysts

Somatic cell nuclear transfer (scNT) embryos suffer from damage caused by micro-operation (manipulation) and inefficient genome reprograming that hinder their normal development at different levels and in distinct ways. These two effects are inseparable in the nature of the scNT embryo, although methods to separately measure them are needed to improve scNT technology and evaluate incoming reprogramming tools. As an attempt to meet these demands, we made bovine sham nuclear-transfer (shNT) blastocysts, special embryos made with a standard nuclear-transfer procedure at the zygote stage, while retaining an intact genome. We compared their transcriptomes with those of other blastocysts derived by in-vitro fertilization (IVF) or scNT. Correlation analysis revealed a singularity of shNT blastocysts as they separately gathered from the others. Analysis of developmentally important genes revealed that, in shNTs, the stemness-associated differentially expressed genes (DEGs), including OCT4, were mostly underrepresented. Overrepresented epi-driver genes were largely associated with heterochromatin establishment and maintenance. By multilateral comparisons of their transcriptomes, we classified DEGs into three groups: 561 manipulation-associated DEGs (MADs) common to shNTs and scNTs, 764 donor genome-associated DEGs (DADs) specific to scNTs, and 1743 zygote manipulation-associated DEGs (zMADs) specific to shNTs. GO enrichment analysis generated various terms involving “cell-cell adhesion,” “translation,” and “transcription” for MADs and “cell differentiation” and “embryo implantation” for DADs. Because of the transcriptomic specificity of shNTs, we studied zMADs in detail. GO enrichment analysis with the 854 zMADs underrepresented in shNTs yielded terms related to protein and mitochondria homeostasis, while GO enrichment analysis of 889 shNT-high zMADs yielded terms related to endoplasmic reticulum stress and protein transport. We summarized the DEGs, which, with further investigation, may help improve our understanding of molecular events occurring in cloned embryos and our ability to control clonal reprogramming.

SV40 Large T Antigen Disrupts Embryogenesis of Canine and Porcine Somatic Cell Nuclear Transfer Embryo

Background

Somatic cell nuclear transfer (SCNT) is a useful biotechnological tool for transgenic animal production using genetically modified somatic cells (GMSCs). However, there are several limitations preventing successful transgenic animal generation by SCNT, such as obtaining proper somatic donor cells with a sufficiently long life span and proliferative capacity for generating GMSCs. Here, we established simian virus 40 large T antigen (SV40LT)-mediated lifespan-extended canine fibroblast cells (SV40LT-K9 cells) and evaluated their potential as nuclei donors for SCNT, based on cellular integrity and SCNT embryo development.

Results

SV40LT did not cause canine cell transformation, based on cell morphology and proliferation rate. No anchorage-independent growth in vitro and tumorigenicity in vivo were observed. After SCNT with SV40LT-K9 cells, embryos were transferred into surrogate dogs. All dogs failed to become pregnant. Most embryos did not proceed past the 8-cell stage and only one surrogate showed an implantation trace in its oviduct, indicating that the cells rarely developed into blastocysts. Because of the absence of an in vitro maturation method for canine embryos, we performed identical experiments using porcine fibroblast cells. Similarly, SV40LT did not transform porcine fibroblast cells (SV40LT-Pig cells). During in vitro development of SV40LT-Pig cell-driven SCNT embryos, their blastocyst formation rate was clearly lower than those of normal cells. Karyotyping analysis revealed that both SV40LT-K9 and SV40LT-Pig cells had aberrant chromosomal statuses.

Conclusions

Although lifespan-extended canine and porcine cells via SV40LT exhibit no apparent transforming changes, they are inappropriate for use as nuclei donors for SCNT because of their aneuploidy.

Supplement of autologous ooplasm into porcine somatic cell nuclear transfer embryos does not alter embryo development

Somatic cell nuclear transfer (SCNT) is considered as the technique in which a somatic cell is introduced into an enucleated oocyte to make a cloned animal. However, it is unavoidable to lose a small amount of the ooplasm during enucleation step during SCNT procedure. The present study was aimed to uncover whether the supplement of autologous ooplasm could ameliorate the oocyte competence so as to improve low efficiency of embryo development in porcine SCNT. Autologous ooplasm-transferred (AOT) embryos were generated by the supplementation with autologous ooplasm into SCNT embryos. They were comparatively evaluated with respect to embryo developmental potential, the number of apoptotic body formation and gene expression including embryonic lineage differentiation, apoptosis, epigenetics and mitochondrial activity in comparison with parthenogenetic, in vitro-fertilized (IVF) and SCNT embryos. Although AOT embryos showed perfect fusion of autologous donor ooplasm with recipient SCNT embryos, the supplement of autologous ooplasm could not ameliorate embryo developmental potential in regard to the rate of blastocyst formation, total cell number and the number of apoptotic body. Furthermore, overall gene expression of AOT embryos was presented with no significant alterations in comparison with that of SCNT embryos. Taken together, the results of AOT demonstrated inability to make relevant values improved from the level of SCNT embryos to their IVF counterparts.

Breeding animals for quality products: not only genetics

The effect of the Developmental Origins of Health and Disease on the spread of non-communicable diseases is recognised by world agencies such as the United Nations and the World Health Organization. Early environmental effects on offspring phenotype also apply to domestic animals and their production traits. Herein, we show that maternal nutrition not only throughout pregnancy, but also in the periconception period can affect offspring phenotype through modifications of gametes, embryos and placental function. Because epigenetic mechanisms are key processes in mediating these effects, we propose that the study of epigenetic marks in gametes may provide additional information for domestic animal selection.

Synergies between assisted reproduction technologies and functional genomics

This review, is a synopsis of advanced reproductive technologies in farm animals, including the discussion of their limiting factors as revealed by the study of offspring derived from embryos produced in vitro and through cloning. These studies show that the problems of epigenetic mis-programming, which were reported in the initial stages of assisted reproduction, still persist. The importance of whole-genome analyses, including the methylome and transcriptome, in improving embryo biotechnologies in farm animals, are discussed. Genome editing approaches for the improvement of economically-relevant traits in farm animals are also described. Efficient farm animal embryo biotechnologies, including cloning and the most recent technologies such as genome editing, will effectively complement the latest strategies to accelerate genetic improvement of farm animals.

Genome Editing in Large Animals

Genome editing in large animals has tremendous practical applications, from more accurate models for medical research through improved animal welfare and production efficiency. Although genetic modification in large animals has a 30 year history, until recently technical issues limited its utility. The original methods - pronuclear injection and integrating viruses - were plagued with problems associated with low efficiency, silencing, poor regulation of gene expression, and variability associated with random integration. With the advent of site specific nucleases such as TALEN and CRISPR/Cas9, precision editing became possible. When used on their own, these can be used to truncate or knockout genes through non-homologous end joining (NHEJ) with relatively high efficiency. When used with a template containing desired gene edits, these can be used to allow insertion of any desired changes to the genome through homologous recombination (HR) with substantially lower efficiency. Consideration must be given to the issues of marker sets and off-target effects. Somatic cell nuclear transfer is most commonly used to create animals from gene edited cells, but direct zygote injection and use of spermatogonial stem cells are alternatives under development. In developing gene editing projects, priority must be given to understanding the potential for off-target or unexpected effects of planned edits, which have been common in the past. Because of the increasing technical sophistication with which it can be accomplished, genome editing is poised to revolutionize large animal genetics, but attention must be paid to the underlying biology in order to maximize benefit.