Interspecies somatic cell nuclear transfer: a salvage tool seeking first aid

FOGS: A SNPSTR Marker Database to Combat Wildlife Trafficking and a Cell Culture Bank for Ex-Situ Conservation

Illegal wildlife trade is a growing problem internationally. Poaching of animals not only leads to the extinction of populations and species but also has serious consequences for ecosystems and economies. This study introduces a molecular marker system that authorities can use to detect and substantiate wildlife trafficking. SNPSTR markers combine short tandem repeats with single nucleotide polymorphisms within an amplicon to increase discriminatory power. Within the FOGS (Forensic Genetics for Species Protection) project, we have established SNPSTR marker sets for 74 vertebrate species. On average, each set consists of 19 SNPSTR markers with 82 SNPs per set. More than 1300 SNPSTR markers and over 300 STR markers were identified. Also, through its biobanking pipeline, the FOGS project enabled the cryopreservation of somatic cells from 91 vertebrate species as well as viable tissues for later cell initiation from a further 109 species, providing future strategies for ex situ conservation. In addition, many more fixed tissues and DNA samples of endangered species were biobanked. Therefore, FOGS was an interdisciplinary study, combining molecular wildlife forensics and conservation tools. The SNPSTR sets and cell culture information are accessible through the FOGS database (https://fogs-portal.de/data) that is open to scientists, researchers, breeders and authorities worldwide to protect wildlife from illegal trade.

Conservation Mitonuclear Replacement: Facilitated mitochondrial adaptation for a changing world

Most species will not be able to migrate fast enough to cope with climate change, nor evolve quickly enough with current levels of genetic variation. Exacerbating the problem are anthropogenic influences on adaptive potential, including the prevention of gene flow through habitat fragmentation and the erosion of genetic diversity in small, bottlenecked populations. Facilitated adaptation, or assisted evolution, offers a way to augment adaptive genetic variation via artificial selection, induced hybridization, or genetic engineering. One key source of genetic variation, particularly for climatic adaptation, are the core metabolic genes encoded by the mitochondrial genome. These genes influence environmental tolerance to heat, drought, and hypoxia, but must interact intimately and co-evolve with a suite of important nuclear genes. These coadapted mitonuclear genes form some of the important reproductive barriers between species. Mitochondrial genomes can and do introgress between species in an adaptive manner, and they may co-introgress with nuclear genes important for maintaining mitonuclear compatibility. Managers should consider the relevance of mitonuclear genetic variability in conservation decision-making, including as a tool for facilitating adaptation. I propose a novel technique dubbed Conservation Mitonuclear Replacement (CmNR), which entails replacing the core metabolic machinery of a threatened species-the mitochondrial genome and key nuclear loci-with those from a closely related species or a divergent population, which may be better-adapted to climatic changes or carry a lower genetic load. The most feasible route to CmNR is to combine CRISPR-based nuclear genetic editing with mitochondrial replacement and assisted reproductive technologies. This method preserves much of an organism's phenotype and could allow populations to persist in the wild when no other suitable conservation options exist. The technique could be particularly important on mountaintops, where rising temperatures threaten an alarming number of species with almost certain extinction in the next century.

In vitro and in vivo development of interspecies Asian elephant embryos reconstructed with pig enucleated oocytes

Interspecies somatic cell nuclear transfer (iSCNT) has an immense potential to rescue endangered animals and extinct species like mammoths. In this study, we successfully established an Asian elephant's fibroblast cell lines from ear tissues, performed iSCNT with porcine oocytes and evaluated the in vitro and in vivo development of reconstructed embryos. A total of 7780 elephant-pig iSCNT embryos were successfully reconstructed and showed in vitro development with cleavage rate, 4-cell, 8-cell and blastocyst rate of 73.01, 30.48, 5.64, and 4.73%, respectively. The total number of elephant-pig blastocyte cells and diameter of hatched blastocyte was 38.67 and 252.75 μm, respectively. Next, we designed species-specific markers targeting EDNRB, AGRP and TYR genes to verify the genome of reconstructed embryos with donor nucleus/species. The results indicated that 53.2, 60.8, and 60.8% of reconstructed embryos (n = 235) contained elephant genome at 1-cell, 2-cell and 4-cell stages, respectively. However, the percentages decreased to 32.3 and 32.7% at 8-cell and blastocyst stages, respectively. Furthermore, we also evaluated the in vivo development of elephant-pig iSCNT cloned embryos and transferred 2260 reconstructed embryos into two surrogate gilts that successfully became pregnant and a total of 11 (1 and 10) fetuses were surgically recovered after 17 and 19 days of gestation, respectively. The crown-rump length and width of elephant-pig cloned fetuses were smaller than the control group. Unfortunately, none of these fetuses contained elephant genomes, which suggested that elephant embryos failed to develop in vivo. In conclusion, we successfully obtained elephant-pig reconstructed embryos for the first time and these embryos are able to develop to blastocyst, but the in vivo developmental failure needs further investigated.

Bovid Interspecies Somatic Cell Nuclear Transfer with Ooplasm Transfer

Interspecies somatic cell nuclear transfer (iSCNT) contributes to the preservation of endangered species, albeit nuclear-mitochondrial incompatibilities constrain its application. iSCNT, coupled with ooplasm transfer (iSCNT-OT), has the potential to overcome the challenges associated with species- and genus-specific differences in nuclear-mitochondrial communication. Our iSCNT-OT protocol combines the transfer of both bison (Bison bison bison) somatic cell and oocyte ooplasm by a two-step electrofusion into bovine (Bos taurus) enucleated oocytes. The procedures described herein could be used in further studies to determine the effects of crosstalk between nuclear and ooplasmic components in embryos carrying genomes from different species.

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.

Knockdown of YY1 Inhibits XIST Expression and Enhances Cloned Pig Embryo Development

The technique of cloning has wide applications in animal husbandry and human biomedicine. However, the very low developmental efficiency of cloned embryos limits the application of cloning. Ectopic XIST-expression-induced abnormal X chromosome inactivation (XCI) is a primary cause of the low developmental competence of cloned mouse and pig embryos. Knockout or knockdown of XIST improves cloning efficiency in both pigs and mice. The transcription factor Yin yang 1(YY1) plays a critical role in XCI by triggering the transcription of X-inactive specific transcript (XIST) and facilitating the localization of XIST RNA on the X chromosome. This study aimed to investigate whether RNA interference to suppress the expression of YY1 can inhibit erroneous XIST expression, rescue abnormal XCI, and improve the developmental ability of cloned pig embryos. The results showed that YY1 binds to the 5' regulatory region of the porcine XIST gene in pig cells. The microinjection of YY1 siRNA into cloned pig embryos reduced the transcript abundance of XIST and upregulated the mRNA level of X-linked genes at the 4-cell and blastocyst stages. The siRNA-mediated knockdown of YY1 altered the transcriptome and enhanced the in vitro and in vivo developmental efficiency of cloned porcine embryos. These results suggested that YY1 participates in regulating XIST expression and XCI in cloned pig embryos and that the suppression of YY1 expression can increase the developmental rate of cloned pig embryos. The present study established a new method for improving the efficiency of pig cloning.

Low Expression of Mitofusin 1 Gene Leads to Mitochondrial Dysfunction and Embryonic Genome Activation Failure in Ovine-Bovine Inter-Species Cloned Embryos

Inter-species somatic cell nuclear transfer (iSCNT) is significant in the study of biological problems such as embryonic genome activation and the mitochondrial function of embryos. Here, we used iSCNT as a model to determine whether abnormal embryo genome activation was caused by mitochondrial dysfunction. First, we found the ovine-bovine iSCNT embryos were developmentally blocked at the 8-cell stage. The reactive oxygen species level, mitochondrial membrane potential, and ATP level in ovine-bovine cloned embryos were significantly different from both bovine-bovine and IVF 8-cell stage embryos. RNA sequencing and q-PCR analysis revealed that mitochondrial transport, mitochondrial translational initiation, mitochondrial large ribosomal subunit, and mitochondrial outer membrane genes were abnormally expressed in the ovine-bovine embryos, and the mitochondrial outer membrane and mitochondrial ribosome large subunit genes, mitochondrial fusion gene 1, and ATPase Na+/K+ transporting subunit beta 3 gene were expressed at lower levels in the ovine-bovine cloned embryos. Furthermore, we found that overexpression and knockdown of Mfn1 significantly affected mitochondrial fusion and subsequent biological functions such as production of ATP, mitochondrial membrane potential, reactive oxygen species and gene expressions in cloned embryos. These findings enhance our understanding of the mechanism by which the Mfn1 gene regulates embryonic development and embryonic genome activation events.

Global DNA methylation profiles of buffalo (Bubalus bubalis) preimplantation embryos produced by handmade cloning and in vitro fertilization

Somatic cell nuclear transfer technique (SCNT) has proved to be an outstanding method of multiplication of elite animals but accompanied with low efficiency and live birth rate of cloned animals. Epigenetic alterations of DNA has been one of the culprits behind this issue. Cloned embryos are found to deviate slightly from regular pattern of demethylation and re-methylation at the time of nuclear reprogramming and embryonic development when compared with embryos produced by in vitro fertilization (IVF). Thus, the present study was aimed at evaluating global DNA methylation profiles of cloned embryos at 2-cell, 8-cell and blastocyst stages and compare it with corresponding stages of embryos produced by IVF by using MeDIP-Sequencing on Illumina-based platform. We found out that cloned embryos exhibited significantly different DNA methylation pattern as compared to IVF embryos with respect to distribution of differentially methylated regions in different components of genome, CpG islands distribution and methylation status, gene ontological profiles and pathways affected throughout the developmental stages. The data generated from MeDIP-Seq was validated at blastocyst stage cloned and IVF embryos by bisulfite-sequencing PCR on five randomly selected gene regions.

Global MicroRNA Expression Profiling of Buffalo (Bubalus bubalis) Embryos at Different Developmental Stages Produced by Somatic Cell Nuclear Transfer and In-Vitro Fertilization Using RNA Sequencing

Despite the success of cloning technology in the production of offspring across several species, its application on a wide scale is severely limited by the very low offspring rate obtained with cloned embryos. The expression profile of microRNAs (miRNAs) in cloned embryos throughout embryonic development is reported to deviate from regular patterns. The present study is aimed at determining the dynamics of the global expression of miRNA profile in cloned and in-vitro fertilization (IVF) pre-implantation embryos at different developmental stages, i.e., the two-cell, eight-cell, and blastocyst stages, using next-generation sequencing. The results of this study suggest that there is a profound difference in global miRNA profile between cloned and IVF embryos. These differences are manifested throughout the course of embryonic development. The cloned embryos differ from their IVF counterparts in enriched Gene Ontology (GO) terms of biological process, molecular function, cellular component, and protein class categories in terms of the targets of differentially expressed miRNAs. The major pathways related to embryonic development, such as the Wnt signaling pathway, the apoptosis signaling pathway, the FGF signaling pathway, the p53 pathway, etc., were found to be affected in cloned relative to IVF embryos. Overall, these data reveal the distinct miRNA profile of cloned relative to IVF embryos, suggesting that the molecules or pathways affected may play an important role in cloned embryo development.

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.

Isolation and characterization mesenchymal stem cells from red panda (Ailurus fulgens styani) endometrium

Endometrial mesenchymal stem cells (eMSCs) are undifferentiated endometrial cells with self-renewal, multidirectional differentiation and high proliferation potential. Nowadays, eMSCs have been found in a few species, but it has never been reported in endangered wild animals, especially the red panda. In this study, we successfully isolated and characterized the eMSCs derived from red panda. Red panda eMSCs were fibroblast-like, had a strong proliferative potential and a stable chromosome number. Pluripotency genes including Klf4, Sox2 and Thy1 were highly expressed in eMSCs. Besides, cultured eMSCs were positive for MSC markers CD44, CD49f and CD105 and negative for endothelial cell marker CD31 and haematopoietic cell marker CD34. Moreover, no reference RNA-seq was used to analyse the eMSCs transcriptional expression profile and key pathways. Compared with skin fibroblast cell group, 9104 differentially expressed genes (DEGs) were identified, among which are 5034 genes upregulated, 4070 genes downregulated and the top 20 enrichment pathways of DEGs in Gene Ontology (GO) and the Kyoto Encyclopedia of Genes Genomes (KEGG) mainly associated with G-protein coupled receptor signalling pathway, carbohydrate derivative binding, nucleoside binding, ribosome biogenesis, cell cycle, DNA replication, Ras signalling pathway and purine metabolism. Among the DEGs, some representative genes about promoting MSCs differentiation and proliferation were upregulated and promoting fibroblasts proliferation were downregulated in eMSCs group. Red panda eMSCs also had multiple differentiation ability and could differentiate into adipocytes, chondrocytes and hepatocytes. In conclusion, we, for the first time, isolated and characterized the red panda eMSCs with ability of multiplication and multilineage differentiation in vitro. The new multipotential stem cell could be beneficial not only for the germ plasm resources conservation of red panda, but also for basic or pre-clinical studies in the future.

C23 gene regulates the nucleolin structure and biosynthesis of ribosomes in bovine intraspecific and interspecific somatic cell nuclear transfer embryos

Somatic cell nuclear transfer (SCNT) can reprogram differentiated somatic cells to produce individual animals, thus having advantages in animal breeding and chromatin reprogramming. Interspecies SCNT (iSCNT) provides extreme cases of reprogramming failure that can be used to understand the basic biological mechanism of genome reprogramming. It is important to understand the possible mechanisms for the failure of zygotic genome activation (ZGA) in iSCNT embryos in order to improve the efficiency of SCNT embryos. In the present study, we compared the development of bovine-bovine (B-B), ovine-ovine (O-O) SCNT, and ovine-bovine (O-B) iSCNT embryos and found that a developmental block existed in the 8-cell stage in O-B iSCNT embryos. RNA sequencing and q-PCR analysis revealed that the large ribosomal subunit genes (RPL) or the small ribosomal subunit genes (RPS) were expressed at lower levels in the O-B iSCNT embryos. The nucleolin (C23) gene that regulates the ribosomal subunit generation was transcribed at a lower level during embryonic development in O-B iSCNT embryos. In addition, the nucleolin exhibited a clear circular-ring structure in B-B 8-cell stage embryos, whereas this was shell-like or dot-like in the O-B embryos. Furthermore, overexpression of C23 could increase the blastocyst rate of both SCNT and iSCNT embryos and partly rectify the ring-like nucleolin structure and the expression of ribosomal subunit related genes were upregulation, while knockdown of C23 increased the shell-like nucleolin-structure in B-B cloned embryos and downregulated the expression of ribosomal subunit related genes. These results implied that abnormal C23 and ribosome subunit gene expression would lead to the developmental block of iSCNT embryos and ZGA failure. Overexpression of the C23 gene could partly improve the blastocyst development and facilitate the nucleolin structure in bovine preimplantation SCNT embryos.

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.

Functions and Regulation of Endogenous Retrovirus Elements during Zygotic Genome Activation: Implications for Improving Somatic Cell Nuclear Transfer Efficiency

Endogenous retroviruses (ERVs), previously viewed as deleterious relics of ancestral retrovirus infections, are silenced in the vast majority of cells to minimize the risk of retrotransposition. Counterintuitively, bursts of ERV transcription usually occur during maternal-to-zygotic transition (MZT) in preimplantation embryos; this is regarded as a major landmark event in the zygotic genome activation (ZGA) process, indicating that ERVs play an active part in ZGA. Evolutionarily, the interaction between ERVs and hosts is mutually beneficial. The endogenization of retrovirus sequences rewires the gene regulatory network during ZGA, and ERV repression may lower germline fitness. Unfortunately, owing to various limitations of somatic cell nuclear transfer (SCNT) technology, both developmental arrest and ZGA abnormalities occur in a high percentage of cloned embryos, accompanied by ERV silencing, which may be caused by the activation failure of upstream ERV inducers. In this review, we discuss the functions and regulation of ERVs during the ZGA process and the feasibility of temporal control over ERVs in cloned embryos via exogenous double homeobox (DUX). We hypothesize that further accurate characterization of the ERV-rewired gene regulatory network during ZGA may provide a novel perspective on the development of preimplantation embryos.

Mitochondrial metabolism assessment of lycaon-dog fetuses in interspecies somatic cell nuclear transfer

Many studies have reported that interspecies somatic cell nuclear transfer (iSCNT) is considered the prominent method in preserving endangered animals. However, the development rate of iSCNT embryos is low, and there are limited studies on the molecular mechanism of the iSCNT process. This study evaluated the developmental potential of interspecies lycaon (Lycaon pictus)-dog embryos and assessed the mitochondrial content and metabolism of the produced cloned lycaon-dog fetus. Of 678 collected oocytes, 516 were subjected to nuclear transfer, and 419 reconstructed embryos with male lycaon fibroblasts were transferred into 27 surrogates. Of 720 oocytes, 568 were subjected to nuclear transfer and 469 reconstructed embryos with female lycaon fibroblasts were transferred into 31 surrogates. Two recipients who received female reconstructed embryos were identified as pregnant at 30 days. However, fetal retardation with no cardiac activity was observed at 46 days. Microsatellite analysis confirmed that the cloned lycaon-dog fetus was genetically identical to the lycaon donor cell, whereas mitochondrial sequencing analysis revealed that oocyte donor dogs transmitted their mtDNA. We assessed the oxygen consumption rate and mitochondrial content of the aborted lycaon-dog fetus to shed some light on the aborted fetus's cellular metabolism. The oxygen consumption rates in the lycaon-dog fetal fibroblasts were lower than those in adult dog, lycaon and cloned dog fetal fibroblasts. Furthermore, lycaon-dog fetal fibroblasts showed decreased proportions of live and active mitochondria compared with other groups. Overall, we hypothesized that nuclear-mitochondrial incompatibility affects pyruvate metabolism and that these processes cause intrauterine fetal death.

Effects of treatment with a microRNA mimic or inhibitor on the developmental competence, quality, epigenetic status and gene expression of buffalo (Bubalus bubalis) somatic cell nuclear transfer embryos

Expression levels of 13 microRNAs (miRNAs) were compared between buffalo blastocysts produced by somatic cell nuclear transfer through hand-made cloning and IVF to improve cloning efficiency. Expression of miR-22, miR-145, miR-374a and miR-30c was higher, whereas that of miR-29b, miR-101, miR-302b, miR-34a, miR-21 and miR-25 was lower, in nuclear transferred (NT) than IVF embryos; the expression of miR-200b, miR-26a and miR-128 was similar between the two groups. Based on these, miR-145, which is involved in the regulation of pluripotency, was selected for further investigation of NT embryos. miR-145 expression was lowest at the 2-cell stage, increased through the 4-cell stage and was highest at the 8-cell or morula stage in a pattern that was similar between NT and IVF embryos. miR-145 expression was higher in NT than IVF embryos at all stages examined. Treatment of reconstructed embryos 1h after electrofusion with an inhibitor of miR-145 for 1h decreased the apoptotic index and increased the blastocyst rate, total cell number, ratio of cells in the inner cell mass to trophectoderm, global levels of acetylation of histone 3 at lysine 18 and expression of Krueppel-like factor 4 (KLF4), octamer-binding transcription factor 4 (OCT4) and SRY (sex determining region Y)-box 2 (SOX2) in blastocysts. Treatment with an miR-145 mimic had the opposite effects. In conclusion, treatment of NT embryos with an miR-145 inhibitor improves the developmental competence and quality, and increases histone acetylation and expression of pluripotency-related genes.

The perspective of the incompatible of nucleus and mitochondria in interspecies somatic cell nuclear transfer for endangered species

Taking into account the latest Red List of the International Union for Conservation of Nature in which 25% of all mammals are threatened with extinction, somatic cell nuclear transfer (SCNT) could be a beneficial tool and holds a lot of potential for aiding the conservation of endangered, exotic or even extinct animal species if somatic cells of such animals are available. In the case of shortage and sparse amount of wild animal oocytes, interspecies somatic cell nuclear transfer (iSCNT), where the recipient ooplasm and donor nucleus are derived from different species, is the alternative SCNT technique. The successful application of iSCNT, resulting in the production of live offspring, was confirmed in several combination of closely related species. When nucleus donor cells and recipient oocytes have been used in many other combinations, very often with a very distant taxonomical relation iSCNT resulted only in the very early stages of cloned embryo development. Problems encountered during iSCNT related to mitochondrial DNA (mtDNA)/genomic DNA incompatibility, mtDNA heteroplasmy, embryonic genome activation of the donor nucleus by the recipient oocyte and availability of suitable foster mothers for iSCNT embryos. Implementing assisted reproductive technologies, including iSCNT, to conservation programmes also raises concerns that the production of genetically identical populations might cause problems with inbreeding. The article aims at presenting achievements, limitations and perspectives of iSCNT in maintaining animal biodiversity.

Embryo aggregation allows the production of kodkod (Leopardus guigna) blastocysts after interspecific SCNT

The kodkod (Leopardus guigna) is a small felid endemic of Chile and is considered a vulnerable species. Domestic cat oocytes have been successfully used as recipient cytoplast to reprogram somatic cells from different felids by interspecific somatic cell nuclear transfer (iSCNT). The developmental competence of felid embryos generated by iSCNT can be improved by the aggregation method using a zona-free culture system. The objective of this research was to evaluate the developmental competence of kodkod embryos generated by iSCNT using domestic cat oocytes and the aggregation method. For this purpose, five experimental group were done: (1) cat embryos generated by IVF, (2) cat embryos generated by SCNT (Ca1x), (3) aggregated cat embryos generated by SCNT (Ca2x), (4) kodkod embryos generated by iSCNT (K1x) and (5) aggregated kodkod embryos generated by iSCNT (K2x). Cleavage, morulae and blastocyst rates were estimated. The blastocyst diameter was evaluated. The gene expression level of pluripotency (OCT4, SOX2 and NANOG) and differentiation markers (CDX2 and GATA6) was analyzed in blastocysts. Morulae rate was higher in the IVF group and when cloned embryos were cultured in aggregates (IVF: 68.2%, Ca2x: 58.0% and K2x: 62.4%) compared to individually cultured kodkod embryos (K1x: 37.0%) (P < 0.05). Embryo aggregation increased blastocysts formation in the Ca2x group (30.9%) to a similar rate compared to the IVF group (44.5%) (P > 0.05). No blastocysts were generated in the K1x group, whereas blastocysts formation was obtained in K2x group (5.9%). The diameter of blastocysts from the K2x group (172.8 μm) was significantly lower than blastocysts from the Ca2x group (P < 0.05). The relative expression of OCT4 was lower in blastocysts from Ca1x than in blastocysts from IVF (P < 0.05). Furthermore, CDX2 expression was lower in blastocysts from Ca2x than in blastocysts from Ca1x and IVF groups (P < 0.05). In kodkod embryos, only one blastocyst from the K2x group expressed OCT4. No expression of SOX2, NANOG, CDX2 and GATA6 was detected in kodkod blastocysts. In conclusion, after iSCNT, domestic cat oocytes support the development of kodkod embryos until the morula stage. The aggregation method increases the morulae rate of kodkod cloned embryos and allows blastocysts formation. However, kodkod blastocysts have a poor morphological quality and a lacking expression of pluripotency and differentiation markers, probably caused by an incomplete nuclear reprogramming.

Post-mortem recovery, in vitro maturation and fertilization of fallow deer (Dama dama, Linnaeus 1758) oocytes collected during reproductive and no reproductive season

Habitat degradation leads to small and fragmented populations, lower genetic variability and fertility overtime. Assisted reproductive techniques represent important tools to cope with the dramatic loss of biodiversity. Fallow deer (Dama dama), beyond its high commercial value and wide distribution, may represent the most suitable model to study endangered cervids. In this study, oocytes were recovered post-mortem from fallow deer during the breeding and no breeding seasons and were in vitro matured (IVM). The ability of cryopreserved thawed sperm samples recovered by electroejaculation from four adult males was tested by in vitro fertilization of IVM oocytes. The number of oocytes collected per ovary did significantly vary across seasons from 6.2 ± 0.92 during breeding season to 10.4 ± 1.26 during no breeding season (p = .006). Oocytes collected during the breeding season showed higher in vitro fertilization rate compared to the no breeding season (p = .045). However, no embryos reached the blastocyst stage. Semen samples obtained by electroejaculation were successfully cryopreserved, although the cryopreservation process negatively affected most kinetic parameters, mainly at 2 hr post-thawing. Moreover, the percentage of rapid spermatozoa significantly decreased between fresh samples and at 2 hr post-thawing, whereas the percentage of slow spermatozoa increased across the same period (p < .05). Our study provides the logistic steps for the application of assisted reproductive techniques in fallow deer and might be of great interest for genetic resource bank planning.

Effect of Dickkopf-1 and colony stimulating factor-2 on the developmental competence, quality, gene expression and live birth rate of buffalo (Bubalus bubalis) embryos produced by hand-made cloning

A functional canonical WNT signaling pathway exists in preimplantation embryos and inhibits embryonic development. Recent studies suggest that this pathway is over-expressed in nuclear transferred (NT), compared to IVF embryos. The present study investigated the effects of Dickkopf-1 (DKK1), an inhibitor of canonical WNT signaling pathway and colony stimulating factor-2 (CSF2), an embryokine, on the developmental competence, quality, gene expression and live birth rate of NT buffalo embryos produced by Hand-made cloning (HMC). Following supplementation of the in vitro culture medium on day 5 with DKK1 (100 ng/mL), CSF2 (10 ng/mL), DKK1+CSF2 or no supplementation (control), the blastocyst rate was higher (P < 0.05) with DKK1 and DKK1+CSF2 (42.6 ± 1.4% and 46.6 ± 0.9%, respectively) than with CSF2 or controls (40.6 ± 1.3% and 39.0 ± 1.3%, respectively). The apoptotic index of the blastocysts was lower (P < 0.05) for DKK1, CSF2 and DKK1+CSF2 groups (3.44 ± 0.14, 3.39 ± 0.11 and 3.11 ± 0.22, respectively) compared to controls (6.64 ± 0.25), and was similar to that of the IVF blastocysts (3.67 ± 0.18). Although the total cell number was similar for the DKK1, CSF2, DKK1+CSF2 and control groups (200.4 ± 3.05, 196.4 ± 3.73, 204.7 ± 3.71 and 205 ± 4.03, respectively), the inner cell mass:trophectoderm cell number ratio of DKK1, CSF2 and DKK1+CSF2 groups (0.21 ± 0.01, 0.17 ± 0.01 and 0.22 ± 0.02, respectively) was higher (P < 0.05) than controls (0.13 ± 0.01) and was similar to that of IVF blastocysts (0.19 ± 0.01). Treatment with DKK1 or CSF2 or both increased (P < 0.05) the expression level of OCT4, NANOG,SOX2, GATA6, BCL2, PTEN, P53, FGF4, GLUT1 and IFN-τ, and decreased that of C-MYC, CDX2, CASPASE, DNMT3a, TCF7 and LEF1 in blastocysts, compared to controls. Transfer of DKK1-treated embryos to 13 recipients resulted in 4 pregnancies (30.8%; 2 live births, one abortion and one currently at 9 months of pregnancy) whereas, transfer of DKK1+CSF2-treated embryos to 16 recipients, resulted in 4 pregnancies (25.0%), all of which resulted in live births. No pregnancy was obtained after transfer of control and CSF-treated embryos to 12 and 16 recipients, respectively. These results suggest that DKK1 treatment of NT embryos increases the blastocyst, conception and live birth rate, and improves their quality whereas, CSF2 treatment, does not affect the blastocyst, conception and live birth rate despite improvement in embryo quality.

Reducing the cytoplasmic volume during hand-made cloning adversely affects the developmental competence and quality, and alters relative abundance of mRNA transcripts and epigenetic status of buffalo (Bubalus bubalis) embryos

Hand-made cloning (HMC) is a method of choice for somatic cell nuclear transfer (SCNT). There is 20% to 50% of cytoplasm lost during manual enucleation of oocytes with HMC. To compensate, two enucleated demicytoplasts, instead of one, are fused with each donor cell, which leads to cytoplasm pooling from two different demicytoplasts. In this study, effects of using one, instead of two demicytoplasts (controls) was examined, for production of embryos using HMC. Use of one demicytoplast decreased blastocyst development (12.7 ± 1.98% compared with 47.6 ± 3.49%, P < 0.001), total cell number (TCN, 167.6 ± 14.66 compared with 335.9 ± 58.96, P < 0.01), apoptotic index (2.11 ± 0.38 compared with 3.43±0.38, P < 0.05) but did not significantly alter inner cell mass:trophectoderm cell number ratio (0.17 ± 0.01 compared with 0.19 ± 0.02) and the global content of H3K9ac and H3K27me3 of blastocysts, compared to controls. There were gene expression alterations in pluripotency- (SOX2 and NANOG but not OCT4), epigenetic- (DNMT1 but not DNMT3a and HDAC1), apoptosis- (CASPASE3 but not BCL-2 and BAX), trophectoderm- (CDX2), development- (G6PD but not GLUT1) and cell cycle check point control-related related genes (P53) compared with controls. Transfer of cloned blastocysts from one demicytoplast (n = 8) to recipients resulted in a live calf birth that after 12 days died whereas, with transfer of control blastocysts (n = 14) there was birth of a healthy calf. In conclusion, use of one, instead of two demicytoplasts for HMC, compromises in vitro developmental competence, and alters expression of several important genes affecting embryo development.

Treatment of Buffalo (Bubalus bubalis) Somatic Cell Nuclear Transfer Embryos with MicroRNA-29b Mimic Improves Their Quality, Reduces DNA Methylation, and Changes Gene Expression Without Affecting Their Developmental Competence

microRNA-29b (miR-29b) plays an important role in controlling DNA methylation in cells. We investigated its role during early embryonic development in buffalo embryos produced by somatic cell nuclear transfer (SCNT) and in vitro fertilization (IVF). miR-29b expression was highest at the 2-cell stage, decreased (p < 0.001) at the 4-cell stage, and remained low thereafter at the 8-cell, morula, and blastocyst stages, showing a similar pattern in cloned and IVF embryos. Treatment of reconstructed embryos with miR-29b mimic for 1 hour after 1 hour of electrofusion increased (p < 0.05) the total cell number and decreased (p < 0.05) the levels of apoptosis and DNA methylation compared with controls. It also increased (p < 0.05) the ratio of inner cell mass:trophectoderm cell numbers of blastocysts compared with controls to the levels observed in IVF blastocysts. However, the blastocyst rate was not affected by treatment with miR-29b mimic (29.0% ± 2.0% vs. 27.0% ± 2.0% for controls). The treatment decreased (p < 0.001) the expression of epigenetic-related genes, DNMT3A and DNMT3B, but not DNMT1, and increased (p < 0.05) that of pluripotency- (NANOG, OCT4, and SOX2) and development-related genes (FGF4 and GLUT1) in blastocysts compared with controls. Our results suggest that miR-29b mimic treatment of reconstructed embryos improves the quality, reduces the level of apoptosis and DNA methylation, and changes gene expression in SCNT blastocysts without affecting the blastocyst rate.

Selection of Reference miRNAs for Relative Quantification in Buffalo (Bubalus bubalis) Blastocysts Produced by Hand-Made Cloning and In Vitro Fertilization

Very low birth rate and a high incidence of abnormalities in offspring born from cloned embryos, which have limited the application of cloning technology on a wide scale, are believed to be because of incomplete or aberrant nuclear reprogramming. MicroRNAs (miRNAs) are involved in regulating a wide range of biological processes including reprogramming and embryonic development. Selection of suitable reference miRNAs is critical for normalization of data for accurate relative quantification of miRNAs by quantitative real-time polymerase chain reaction (qRT-PCR), which is currently the most widely used technique for quantifying miRNAs. This study was aimed at identification of reference miRNAs suitable for normalization of qRT-PCR data from blastocyst-stage buffalo embryos produced by handmade cloning and in vitro fertilization (IVF). RNA isolated from cloned and IVF blastocysts was subjected to next-generation sequencing based on which, 12 highly and most consistently expressed miRNAs, which included miR-92a, miR-423, miR-151, Let-7a, miR-103a, miR-93, miR-16b, miR-25, miR-30e, miR-101, miR-127, and miR-197, were selected as candidates for identification of suitable reference miRNAs using three statistical algorithms namely geNorm, NormFinder, and BestKeeper. Based on consensus of the three algorithms, the combination of miRNAs found to be suitable as reference miRNAs were miR-127 and miR-103 for IVF blastocysts; miR-92a and miR-103 for cloned blastocysts, and miR-103, miR-423, and miR-93 across both IVF and cloned blastocysts. The data of this study can be very useful in miRNA expression analysis of blastocyst-stage cloned and IVF embryos.

Potential role of intraspecific and interspecific cloning in the conservation of wild mammals

Intraspecific and interspecific cloning via somatic cell nuclear transfer (iSCNT) is a biotechnique with great possibilities for wild mammals because it allows the maintenance of biodiversity by recovering species, nuclear reprogramming for the production of pluripotency-induced cells, and studies related to embryonic development. Nevertheless, many areas in cloning, especially those associated with wild mammals, are still in question because of the difficulty in obtaining cytoplasmic donor cells (or cytoplasts). Conversely, donor cell nuclei (or karyoplasts) are widely obtained from the skin of living or post-mortem individuals and often maintained in somatic cell banks. Moreover, the creation of karyoplast–cytoplast complexes by fusion followed by activation and embryo development is one of the most difficult steps that requires further clarification to avoid genetic failures. Although difficult, cloning different species, such as wild carnivores and ungulates, can be successful via iSCNT with embryo development and the birth of offspring. Thus, novel research in the area that contributes to the conservation of biodiversity and knowledge of the physiology of species continues. The present review presents the failures and successes that occurred with the application of the technique in wild mammals, with the goal of helping future work on cloning via iSCNT.

Comparative analysis of buffalo (Bubalus bubalis) non-transgenic and transgenic embryos containing human insulin gene, produced by SCNT

Somatic cell nuclear transfer (SCNT), using transgenic donor cells, is a highly efficient method for producing transgenic embryos. We compared the developmental competence, quality and gene expression of transgenic embryos produced by Hand-made cloning from buffalo fetal fibroblasts (BFFs) containing human insulin gene, with non-transgenic embryos produced from BFFs (Controls). The expression vector (pAcISUBC), constructed by inserting human insulin gene between DNA fragments containing mammary gland-specific buffalo β-lactoglobulin (buBLG) promoter and terminator buBLG 3'UTR regions into pAcGFP-N1 vector, was used for obtaining the 11 kb insert for transfection of BFFs by nucleofection. Presence of the transgene in embryos was confirmed by examining GFP expression by RT-PCR and immunofluorescence. The blastocyst rate was lower (P < 0.05) for transgenic embryos than for controls (35.7 ± 1.8% vs 48.7 ± 2.4%). The apoptotic index was higher (P < 0.05) for transgenic than for control blastocysts which, in turn, was higher (P < 0.05) than for IVF counterparts (6.9 ± 0.9, 3.8 ± 0.5 and 1.8 ± 0.3, respectively). The total cell number was similar for transgenic and non-transgenic blastocysts (143.2 ± 17.0 and 137.2 ± 7.6, respectively). The expression level of pro-apoptotic genes BAX and BID but not that of CASP3 and CASP9, and cell cycle check point control-related gene P53 was higher (P < 0.05), and that of development- (IGF-1R and G6PD) and pluripotency-related gene NANOG was lower (P < 0.05) in transgenic than in control embryos. The expression level of epigenetic-related genes DNMT1, DNMT3a and HDAC1 and pluripotency-related gene OCT4 was similar in the two groups. The expression level of BAX, BID, CASP9, P53, DNMT1 and DNMT3a was higher (P < 0.05) and that of OCT4, NANOG IGF-1R and G6PD was lower (P < 0.05) in cloned transgenic than in IVF blastocysts whereas, that of CASP3 and HDAC1 was similar between the two groups. In conclusion, these results suggest that transgenic embryos produced by SCNT have lower developmental competence and quality, and altered gene expression compared to non-transgenic embryos.

Epigenetic Alteration of Donor Cells with Histone Deacetylase Inhibitor m-Carboxycinnamic Acid Bishydroxymide Improves the In Vitro Developmental Competence of Buffalo (Bubalus bubalis) Cloned Embryos

Epigenetic reprogramming is an indispensable process during the course of mammalian development, but aberrant in cloned embryos. The aim of this study was to examine the effect of donor cell treatment with histone deacetylase (HDAC) inhibitor m-carboxycinnamic acid bishydroxymide (CBHA) on cloned embryo development and establish its optimal concentration. Different concentrations of CBHA (2.5, 5.0, 10.0, and 20.0 μM) were used to treat buffalo adult fibroblast cells for 24 hours and effect on cell proliferation, gene expression, and histone modifications was analyzed. Based on these experiments, the best concentration was chosen to determine the effect of enhanced gene activation mark on developmental rates. Among the different concentrations, CBHA at higher concentration (20 μM) shows the sign of apoptosis and stress as indicated by proliferation rate and gene expression data. CBHA treatment significantly decreased the activity of HDACs and increased the level of gene activation mark H3K9ac and H3K4me3, but could not alter the level of H3K27ac. Based on these experiments, 5 μM CBHA was chosen for treatment of donor cells used for the production of cloned embryos. There was no significant difference in cleavage rate between the control and CBHA treatment group (98.5% ± 1.5% vs. 99.0% ± 1.0%), whereas, blastocyst rate markedly improved (46.65% ± 1.94% vs. 57.18% ± 2.68%). The level of H3K9ac and H3K27me3 did not differ significantly in cloned blastocyst produced from either control or CBHA-treated cells. Altogether, these results suggested that donor cell treatment with CBHA supports the reprogramming process and improves the cloned preimplantation development.

Dog cloning-no longer science fiction

Since the generation of world's first cloned dog, Snuppy, in 2005, somatic cell nuclear transfer (SCNT) in dogs has been widely applied for producing several kinds of dogs with specific objectives. Previous studies have demonstrated that cloned dogs show normal characteristics in growth, blood parameters and behavioural aspect. Also, canine SCNT technique has been applied to propagate working dogs with excellent abilities in fields such as assistance of disabled people, drugs detection and rescue activity. Because dogs have similar habituation properties and share many characteristics including anatomic and physiological aspects with humans, they are also primary candidates for human disease models. Recently, transgenic dogs that express red fluorescent protein gene constitutively and green fluorescent protein gene conditionally have been generated. In addition, transgenic dogs with an overexpression of peroxisome proliferator-activated receptor-alpha in specific muscles were generated to enhance physical performance. In 2017, Snuppy was recloned with markedly increased pregnancy and delivery rates compared to the statistics from when Snuppy was first cloned. Such striking improvements in the cloning of dogs using SCNT procedures suggest that dog cloning could be applied in many fields of biomedical science for human diseases research, and the application of cloning is no longer science fiction.

Buffalo SCNT embryos exhibit abnormal gene expression of ERK/MAPK pathway and DNA methylation

Inhibition of ERK/MAPK pathway has been shown to decrease DNA methylation via down-regulation of DNA methyltransferases (DNMTs) in several studies suggesting that this pathway plays an important role in regulation of DNA methylation. We examined the relative expression level of seven important genes related to ERK/MAPK pathway and DNMTs (DNMT1, DNMT3a and DNMT3b) by quantitative real-time PCR in buffalo blastocysts produced by Hand-made cloning and compared it with that in blastocyst-stage embryos produced by in vitro fertilization (IVF). The expression level of six of seven genes related to ERK/MAPK pathway examined i.e., p21RAS, RAF1, AKT1, ERK2, PIK3R2 and c-Myc was significantly higher (p < 0.05) in cloned than in IVF embryos. However, the expression level of FOS was lower (p < 0.005) in cloned than in IVF embryos. The relative expression level of DNMT3a and DNMT3b but not that of DNMT1 was significantly higher (p < 0.05) in cloned than in IVF embryos. These results indicate that the cloned embryos exhibit an abnormal expression of several important genes related to ERK/MAPK pathway and DNMTs. Although a direct link between ERK/MAPK pathway and DNMTs was not examined in the present study, it can be speculated that ERK/MAPK pathway may have a role in regulating the expression of DNMTs in embryos, as also observed in other tissues.

Use of somatic cell banks in the conservation of wild felids

The conservation of biological resources is an interesting strategy for the maintenance of biodiversity, especially for wild felids who are constantly threatened with extinction. For this purpose, cryopreservation techniques have been used for the long-term storage of gametes, embryos, gonadal tissues, and somatic cells and tissues. The establishment of these banks has been suggested as a practical approach to the preservation of species and, when done in tandem with assisted reproductive techniques, could provide the means for reproducing endangered species. Somatic cell banks have been shown remarkable for the conservation of genetic material of felids; by merely obtaining skin samples, it is possible to sample a large group of individuals without being limited by factors such as gender or age. Thus, techniques for somatic tissue recovery, cryopreservation, and in vitro culture of different wild felids have been developed, resulting in a viable method for the conservation of species. One of the most notable conservation programs for wild felines using somatic samples was the one carried out for the Iberian lynx, the most endangered feline in the world. Other wild felids have also been studied in other continents, such as the jaguar in South America. This review aims to present the technical progress achieved in the conservation of somatic cells and tissues in different wild felids, as well address the progress that has been achieved in a few species.

Suberoylanilide hydroxamic acid during in vitro culture improves development of dog-pig interspecies cloned embryos but not dog cloned embryos

This study was conducted to investigate whether the treatment of dog to pig interspecies somatic cell nuclear transfer (iSCNT) embryos with a histone deacetylase inhibitor, to improve nuclear reprogramming, can be applied to dog SCNT embryos. The dog to pig iSCNT embryos were cultured in fresh porcine zygote medium-5 (PZM-5) with 0, 1, or 10 µM suberoylanilide hydroxamic acid (SAHA) for 6 h, then transferred to PZM-5 without SAHA. Although there were no significant differences in cleavage rates, the rates of 5-8-cell stage embryo development were significantly higher in the 10 µM group (19.5 ± 0.8%) compared to the 0 µM groups (13.4 ± 0.8%). Acetylation of H3K9 was also significantly higher in embryos beyond the 4-cell stage in the 10 µM group compared to the 0 or 1 µM groups. Treatment with 10 µM SAHA for 6 h was chosen for application to dog SCNT. Dog cloned embryos with 0 or 10 µM SAHA were transferred to recipients. However, there were no significant differences in pregnancy and delivery rates between the two groups. Therefore, it can be concluded that although porcine oocytes support nuclear reprogramming of dog fibroblasts, treatment with a histone deacetylase inhibitor that supports nuclear reprogramming in dog to pig iSCNT embryos was not sufficient for reprogramming in dog SCNT embryos.

Effect of Sex of Embryo on Developmental Competence, Epigenetic Status, and Gene Expression in Buffalo (Bubalus bubalis) Embryos Produced by Hand-Made Cloning

Buffalo embryos were produced by hand-made cloning using skin fibroblasts from male and female buffaloes (n = 4 each) as donor cells for examining the effect of sex. Although the rate of blastocyst formation (43.8% ± 1.31% vs. 42.2% ± 1.22%) was similar, the total cell number (333 ± 10.4 vs. 270 ± 10.9) was higher (p < 0.05) whereas the apoptotic index (6.39 ± 0.25 vs. 8.52 ± 0.38) was lower (p < 0.05) for male than for female blastocysts. In the blastocysts, the global level of H3K18ac was found to be in the following order: male>female>IVF (in vitro fertilization) blastocysts (p < 0.05). The global level of H3K9me2 was not significantly different between male and female blastocysts and was higher (p < 0.05) compared with that in their IVF counterparts. The relative mRNA abundance of X-chromosome-linked (XIST, HPRT, PGK, and G6PD), apoptosis- (CASPASE3) and pregnancy-related genes (IFN-τ) was significantly higher (p < 0.05) whereas that of DNMT1 was significantly lower (p < 0.05) in female than in male blastocysts; however, in the case of apoptosis- (BCL-XL) and developmental competence-related genes (IGF1R and OCT4), the expression level was similar between the two groups. The gene expression level of OCT4 and IFN-τ but not of IGF1R was significantly lower (p < 0.05) in cloned than in IVF blastocysts. This study demonstrates that the epigenetic status, quality, and expression level of several genes but not the developmental competence are affected by the sex of cloned embryos.

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

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

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

The application of cloning technology on a large scale is limited by very low offspring rate primarily due to aberrant or incomplete epigenetic reprogramming. Trichostatin A (TSA), a histone deacetylase inhibitor, and 5-aza-2'-deoxycytidine (5-aza-dC), an inhibitor of DNA methyltransferases, are widely used for altering the epigenetic status of cloned embryos. We optimized the doses of these epigenetic modifiers for production of buffalo embryos by handmade cloning and examined whether combined treatment with these epigenetic modifiers offered any advantage over treatment with the individual epigenetic modifier. Irrespective of whether donor cells or reconstructed embryos or both were treated with 50 nM TSA +7.5 nM 5-aza-dC, (1) the blastocyst rate was significantly higher (71.6 ± 3.5, 68.3 ± 2.6, and 71.8 ± 2.4, respectively, vs. 43.1 ± 3.4 for controls, p < 0.05); (2) the apoptotic index was lower (5.4 ± 1.1, 9.5 ± 1.0, and 7.4 ± 1.3, respectively, vs. 19.5 ± 2.1 for controls, p < 0.05) and was similar to that of in vitro fertilization blastocysts (6.0 ± 0.8); (3) the global level of H3K18ac was higher (p < 0.01) and that of H3K27me3 lower (p < 0.05) than in controls and was similar among all treatment groups; and (4) the expression level of epigenetic-(HDAC1, DNMT1, and DNMT3a), pluripotency-(OCT4 and NANOG), and development-related (FGF4) genes, but not that of SOX2 and CDX2, was similar among all treatment groups. These results demonstrate that similar levels of beneficial effects can be obtained following treatment of either donor cells or reconstructed embryos or both with the combination of TSA +5-aza-dC. Therefore, there is no advantage in treating both donor cells and reconstructed embryos when the combination of TSA and 5-aza-dC is used.

In vitro development and cytological quality of inter-species (porcine→bovine) cloned embryos are affected by trichostatin A-dependent epigenomic modulation of adult mesenchymal stem cells

Artificial epigenomic modulation of in vitro cultured mesenchymal stem cells (MSCs) by applying a non-selective HDAC inhibitor, termed TSA, can facilitate more epigenetic reprogramming of transcriptional activity of the somatic cell-descended nuclear genome in NT pig embryos. The results of the present investigation showed that TSA-dependent epigenomic modulation of nuclear donor MSCs highly affects both the in vitro developmental capability and the cytological quality of inter-species (porcine→bovine) cloned embryos. The developmental competences to reach the blastocyst stage among hybrid (porcine→bovine) nuclear-transferred embryos that had been reconstructed with bovine ooplasts and epigenetically modulated porcine MSCs were maintained at a relatively high level. These competences were higher than those noted in studies by other authors, but they were still decreased compared to those of intra-species (porcine) cloned embryos that had been reconstituted with porcine ooplasts and either the cell nuclei of epigenetically transformed MSCs or the cell nuclei of epigenetically non-transformed MSCs. In conclusion, MSCs undergoing TSA-dependent epigenetic transformation were used for the first time as a source of nuclear donor cells not only for inter-species somatic cell cloning in pigs but also for inter-species somatic cell cloning in other livestock species. Moreover, as a result of the current research, efficient sequential physicochemical activation of inter-species nuclear-transferred clonal cybrids derived from bovine ooplasm and porcine MSC nuclei was developed.

Characterization of a very rare case of living ewe-buck hybrid using classical and molecular cytogenetics

The natural occurrence of live hybrid offsprings between sheep and goats has been documented in literature, however all the studies have reported the mating of goats with rams, whereas the reciprocal cross was never documented. This study reports on a very rare case of interspecies hybridization occurred between a ewe (2n = 54, XX) and a buck (2n = 60, XY). The hybrid, born in a German flock under natural conditions, is characterised by an intermediate karyotype (2n = 57, XX). The CBA-banding has shown 3 metacentric and 54 acrocentric chromosomes, whereas the GTG- and RBA-banding have revealed that the autosomes involved in the hybrid combination were CHI1, 3; CHI2, 8 and CHI5, 11 corresponding to the metacentric chromosomes OAR1, OAR2 and OAR3. A tri-colour FISH using chromosome paintings and BAC probes has validated this arrangement. A further FISH analysis has been carried out to analyse the telomeres, which showed a normal structure. Nucleolus organiser-bearing chromosomes were identified as pairs OAR1p(CHI3), OAR2q(CHI2), OAR3q(CHI5), OAR4(CHI4) and OAR25(CHI28), and nuclear associations were found. Sex chromosomes were correctly arranged. The odd number of the karyotype might be responsible for a reduced fertility as consequence of the incorrect chromosomal pairing and/or segregation during the meiosis.

Incompatibility between Nuclear and Mitochondrial Genomes Contributes to an Interspecies Reproductive Barrier

Vertebrate cells carry two different genomes, nuclear (nDNA) and mitochondrial (mtDNA), both encoding proteins involved in oxidative phosphorylation. Because of the extensive interactions, adaptive coevolution of the two genomes must occur to ensure normal mitochondrial function. To investigate whether incompatibilities between these two genomes could contribute to interspecies reproductive barriers, we performed reciprocal mtDNA replacement (MR) in zygotes between widely divergent Mus m. domesticus (B6) and conplastic Mus m. musculus (PWD) mice. Transfer of MR1 cybrid embryos (B6nDNA-PWDmtDNA) supported normal development of F1 offspring with reduced male fertility but unaffected reproductive fitness in females. Furthermore, donor PWD mtDNA was faithfully transmitted through the germline into F2 and F3 generations. In contrast, reciprocal MR2 (PWDnDNA-B6mtDNA) produced high embryonic loss and stillborn rates, suggesting an association between mitochondrial function and infertility. These results strongly suggest that functional incompatibility between nuclear and mitochondrial genomes contributes to interspecies reproductive isolation in mammals.

Gnotobiotic Miniature Pig Interbreed Somatic Cell Nuclear Transfer for Xenotransplantation

Transgenic animal producing technology has improved consistently over the last couple of decades. Among the available methods, somatic cell nuclear transfer (SCNT) technology was officially the most popular. However, SCNT has low efficiency and requires a highly skilled individual. Additionally, the allo-SCNT nuclear reprogramming mechanism is poorly understood in the gnotobiotic miniature pig, which is a candidate for xenotransplantation, making sampling in oocytes very difficult compared to commercial hybrid pigs. Therefore, interbreed SCNT (ibSCNT), which is a combination of miniature pig and commercial pig (Landrace based), was analyzed and was found to be similar to SCNT in terms of the rate of blastocyst formation (12.6% ± 2.9% vs. 15.5% ± 2.2%; p > 0.05). However, a significantly lower fusion rate was observed in the ibSCNT compared to normal SCNT with Landrace pig somatic cells (29.6% ± 0.8% vs. 65.0% ± 4.9%). Thus, the optimization of fusion parameters was necessary for efficient SCNT. Our results further revealed that ibSCNT by the whole-cell intracytoplasmic injection (WCICI) method had a significantly higher blastocyst forming efficiency than the electrofusion method (31.1 ± 8.5 vs. 15.5% ± 2.2%). The nuclear remodeling and the pattern of changes in acetylation at H3K9 residue were similar in both SCNT and ibSCNT embryos.

Rewinding the process of mammalian extinction

With only three living individuals left on this planet, the northern white rhinoceros (Ceratotherium simum cottoni) could be considered doomed for extinction. It might still be possible, however, to rescue the (sub)species by combining novel stem cell and assisted reproductive technologies. To discuss the various practical options available to us, we convened a multidisciplinary meeting under the name "Conservation by Cellular Technologies." The outcome of this meeting and the proposed road map that, if successfully implemented, would ultimately lead to a self-sustaining population of an extremely endangered species are outlined here. The ideas discussed here, while centered on the northern white rhinoceros, are equally applicable, after proper adjustments, to other mammals on the brink of extinction. Through implementation of these ideas we hope to establish the foundation for reversal of some of the effects of what has been termed the sixth mass extinction event in the history of Earth, and the first anthropogenic one. Zoo Biol. 35:280-292, 2016. © 2016 The Authors. Zoo Biology published by Wiley Periodicals, Inc.

A New, Dynamic Era for Somatic Cell Nuclear Transfer?

Cloning animals by somatic cell nuclear transfer (SCNT) has remained an uncontrollable process for many years. High rates of embryonic losses, stillbirths, and postnatal mortality have been typical outcomes. These developmental problems arise from abnormal genomic reprogramming: the capacity of the oocyte to reset the differentiated memory of a somatic cell. However, effective reprogramming strategies are now available. These target the whole genome or single domains such as the Xist gene, and their effectiveness has been validated with the ability of experimental animals to develop to term. Thus, SCNT has become a controllable process that can be used to 'rescue' endangered species, and for biomedical research such as therapeutic cloning and the isolation of induced pluripotent stem cells (iPSCs).

Embryo aggregation does not improve the development of interspecies somatic cell nuclear transfer embryos in the horse

The low efficiency of interspecies somatic cell nuclear transfer (iSCNT) makes it necessary to investigate new strategies to improve embryonic developmental competence. Embryo aggregation has been successfully applied to improve cloning efficiency in mammals, but it remains unclear whether it could also be beneficial for iSCNT. In this study, we first compared the effect of embryo aggregation over in vitro development and blastocyst quality of porcine, bovine, and feline zona-free (ZF) parthenogenetic (PA) embryos to test the effects of embryo aggregation on species that were later used as enucleated oocytes donors in our iSCNT study. We then assessed whether embryo aggregation could improve the in vitro development of ZF equine iSCNT embryos after reconstruction with porcine, bovine, and feline ooplasm. Bovine- and porcine-aggregated PA blastocysts had significantly larger diameters compared with nonaggregated embryos. On the other hand, feline- and bovine-aggregated PA embryos had higher blastocyst cell number. Embryo aggregation of equine-equine SCNT was found to be beneficial for embryo development as we have previously reported, but the aggregation of three ZF reconstructed embryos did not improve embryo developmental rates on iSCNT. In vitro embryo development of nonaggregated iSCNT was predominantly arrested around the stage when transcriptional activation of the embryonic genome is reported to start on the embryo of the donor species. Nevertheless, independent of embryo aggregation, equine blastocyst-like structures could be obtained in our study using domestic feline-enucleated oocytes. Taken together, these results reported that embryo aggregation enhance in vitro PA embryo development and embryo quality but effects vary depending on the species. Embryo aggregation also improves, as expected, the in vitro embryo development of equine-equine SCNT embryos; however, we did not observe positive effects on equine iSCNT embryo development. Among oocytes from domestic animals tested in our study, the feline ooplasm might be the most appropriate recipient to partially allow preimplantation embryo development of iSCNT equine embryos.

A Road Map for 21st Century Genetic Restoration: Gene Pool Enrichment of the Black-Footed Ferret

Interspecies somatic cell nuclear transfer (iSCNT) could benefit recovery programs of critically endangered species but must be weighed with the risks of failure. To weigh the risks and benefits, a decision-making process that evaluates progress is needed. Experiments that evaluate the efficiency and efficacy of blastocyst, fetal, and post-parturition development are necessary to determine the success or failure or species-specific iSCNT programs. Here, we use the black-footed ferret (Mustela nigripes) as a case study for evaluating this emerging biomedical technology as a tool for genetic restoration. The black-footed ferret has depleted genetic variation yet genome resource banks contain genetic material of individuals not currently represented in the extant lineage. Thus, genetic restoration of the species is in theory possible and could help reduce the persistent erosion of genetic diversity from drift. Extensive genetic, genomic, and reproductive science tools have previously been developed in black-footed ferrets and would aid in the process of developing an iSCNT protocol for this species. Nonetheless, developing reproductive cloning will require years of experiments and a coordinated effort among recovery partners. The information gained from a well-planned research effort with the goal of genetic restoration via reproductive cloning could establish a 21st century model for evaluating and implementing conservation breeding that would be applicable to other genetically impoverished species.

Cheetah interspecific SCNT followed by embryo aggregation improves in vitro development but not pluripotent gene expression

The aim of this study was to evaluate the capacity of domestic cat (Dc,Felis silvestris) oocytes to reprogram the nucleus of cheetah (Ch,Acinonyx jubatus) cells by interspecies SCNT (iSCNT), by using embryo aggregation. Dc oocytes werein vitromatured and subjected to zona pellucida free (ZP-free) SCNT or iSCNT, depending on whether the nucleus donor cell was of Dc or Ch respectively. ZP-free reconstructed embryos were then cultured in microwells individually (Dc1X and Ch1X groups) or in couples (Dc2X and Ch2X groups). Embryo aggregation improvedin vitrodevelopment obtaining 27.4, 47.7, 16.7 and 28.3% of blastocyst rates in the Dc1X, Dc2X, Ch1X and Ch2X groups, respectively (P<0.05). Moreover, aggregation improved the morphological quality of blastocysts from the Dc2X over the Dc1X group. Gene expression analysis revealed that Ch1X and Ch2X blastocysts had significantly lower relative expression of OCT4, CDX2 and NANOG than the Dc1X, Dc2X and IVF control groups. The OCT4, NANOG, SOX2 and CDX2 genes were overexpressed in Dc1X blastocysts, but the relative expression of these four genes decreased in the Dc2X, reaching similar relative levels to those of Dc IVF blastocysts. In conclusion, Ch blastocysts were produced using Dc oocytes, but with lower relative expression of pluripotent and trophoblastic genes, indicating that nuclear reprogramming could be still incomplete. Despite this, embryo aggregation improved the development of Ch and Dc embryos, and normalized Dc gene expression, which suggests that this strategy could improve full-term developmental efficiency of cat and feline iSCNT embryos.