Effect of cytoplasmic volume on developmental competence of buffalo (Bubalus bubalis) embryos produced through hand-made cloning

Comparison the effects of 5-Aza-2'-deoxycytidine and zebularine on the in vitro development, blastocyst quality, methylation pattern and conception rate on handmade cloned buffalo embryos

In this study we treated the handmade cloned (HMC) buffalo embryos with the DNA methylation inhibitors; 5-aza-2'-deoxycytidine (AzadC) or Zebularine individually after post-fusion and during in vitro culture till eighth day. The blastocysts production rate significantly improved (p < .01) after treating embryos independently with 5 nM AzadC and 5 nM zebularine compared with 2 and 10 nM AzadC or zebularine groups, respectively. The highest cleavage rates were obtained for 5 nM treatment of AzadC and zebularine compared with other treatments and untreated control group. Quality of blastocysts were evaluated using total cell number (TCN) and the ratio of number of inner cell mass (ICM) cells/total cell number (ICM/TCN). Zebularine treatments (2/5/10 nM) significantly improved both TCN and ICM/TCN ratio compared with AzadC treatments (2/5/10 nM); however, control group TCN and ICM/TCN ratio was found lower. The methylation percentage of pDS4.1 and B. bubalis satellite DNA were comparatively more attenuated with 5 nM zebularine than 5 nM AzadC treatment. The increased in vitro development rates of the treated embryos were correlated with the decreased level of DNA methylation and the improved blastocyst quality. Following transfer of 5 nM zebularine treated embryos to 6 recipients, 4 were found to be pregnant, though the pregnancies were not carried to full term.

Dynamic and aberrant patterns of H3K4me3, H3K9me3, and H3K27me3 during early zygotic genome activation in cloned mouse embryos

Somatic cell nuclear transfer (NT) is associated with aberrant changes in epigenetic reprogramming that impede the development of embryos, particularly during zygotic genome activation. Here, we characterized epigenetic patterns of H3K4me3, H3K9me3, and H3K27me3 in mouse NT embryos up to the second cell cycle (i.e. four-celled stage) during zygotic genome activation. In vivo fertilized and parthenogenetically activated (PA) embryos served as controls. In fertilized embryos, maternal and paternal pronuclei exhibited asymmetric H3K4me3, H3K9me3, and H3K27me3 modifications, with the paternal pronucleus showing delayed epigenetic modifications. Higher levels of H3K4me3 and H3K9me3 were observed in NT and PA embryos than in fertilized embryos. However, NT embryos exhibited a lower level of H3K27me3 than PA and fertilized embryos from pronuclear stage 3 to the four-celled stage. Our finding that NT embryos exhibited aberrant H3K4me3, H3K9me3, and H3K27me3 modifications in comparison with fertilized embryos during early zygotic genome activation help to unravel the epigenetic mechanisms of methylation changes in early NT reprogramming and provide an insight into the role of histone H3 in the regulation of cell plasticity during natural reproduction and somatic cell NT.

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.

Current status of assisted reproductive technologies in buffaloes

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

Genome editing of avian species: implications for animal use and welfare

Avian species are used as model systems in research and have contributed to ground-breaking concepts in developmental biology, immunology, genetics, virology, cancer and cell biology. The chicken in particular is an important research model and an agricultural animal as a major contributor to animal protein resources for the global population. The development of genome editing methods, including CRISPR/Cas9, to mediate germline engineering of the avian genome will have important applications in biomedical, agricultural and biotechnological activities. Notably, these precise genome editing tools have the potential to enhance avian health and productivity by identifying and validating beneficial genetic variants in bird populations. Here, we present a concise description of the existing methods and current applications of the genome editing tools in bird species, focused on chickens, with attention on animal use and welfare issues for each of the techniques presented.

Effects of ovary storage temperature and embryo vitrification on somatic cell nuclear transfer outcomes in goats

Improving the genetic potential of farm animals is one of the primary aims in the field of assisted reproduction. In this regard, somatic cell nuclear transfer (SCNT) can be used to produce a large number of embryos from genetically elite animals. The aims of the present study were to assess the effects of: (1) ovary storage conditions on preimplantation development of recovered oocytes and the freezability of the derived blastocysts; and (2) vitrification of goat SCNT-derived blastocysts on postimplantation development. Goat oocytes were recovered from ovaries and stored under warm (25°C-27°C) or cold (11°C-12°C) conditions before being used to produce SCNT embryos. There were no differences in oocytes recovered from ovaries kept under cold versus warm storage conditions in terms of cleavage (mean (±s.d.) 95.68±1.67% vs 95.91±2.93% respectively) and blastocyst formation (10.69±1.17% vs 10.94±0.9% respectively) rates. The re-expansion rate of vitrified blastocysts was significantly lower for cold- than warm-stored ovaries (66.3±8.7% vs 90±11% respectively). To assess the effects of vitrification on postimplantation development, blastocysts from cold-stored ovaries only were transferred from fresh and vitrified-warmed groups. The pregnancy rate was comparable between the fresh and vitrified-warmed groups (41.65% and 45.45% respectively). In addition, established pregnancy in Day 28-38 and full-term pregnancy rates were similar between the two groups. In conclusion, this study shows similar invitro preimplantation developmental potential of warm- and cold-stored ovaries. This study introduces the vitrification technique as an appropriate approach to preserve embryos produced by SCNT for transfer to recipient goats at a suitable time.

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.

Production of cloned cats using additional complimentary cytoplasm

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

Effects of fusion-activation interval and embryo aggregation on in vitro and in vivo development of bovine cloned embryos

Nuclear reprogramming in somatic cell cloning is one of the key factors for proper development, with variations in the protocol appearing to improve cloning efficiency. This study aimed to determine the effects of two fusion-activation intervals and the aggregation of bovine cloned embryos on subsequent in vitro and in vivo development. Zygotes produced by handmade cloning were exposed to two fusion-activation intervals (2 h or 4 h), and then cultured in microwells either individually (1 × 100%) or after aggregation of two structures (2 × 100%). Zona-intact oocytes and zona-free oocytes and hemi-oocytes were used as parthenote controls under the same fusion-activation intervals. Day-7 cloned blastocysts were transferred to synchronous recipients. Cleavage (Day 2), blastocyst (Day 7) and pregnancy (Day 30) rates were compared by the χ² test (P < .05). Extending fusion-activation interval from 2 to 4 h reduced cleavage (91.0 vs. 74.4%) but not blastocyst (34.8 vs. 42.0%) rates. On a microwell basis, cloned embryo aggregation (2 × 100%) increased cleavage (91.5% vs. 74.4%) and blastocyst (46.0% vs. 31.3%) rates compared to controls (1 × 100%), but did not improve the overall embryo production efficiency on Day 7 (23.0% vs. 31.3%), on a per reconstructed embryo basis, respectively. Treatments had no effects on in vitro developmental kinetics, embryo quality, and in vivo development. In summary, the fusion-activation interval and/or the aggregation of cloned bovine embryos did not affect cloning efficiency based on the in vitro development to the blastocyst stage and on pregnancy outcome.

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

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

Cytoplasmic volume of recipient oocytes affects the nucleus reprogramming and the developmental competence of HMC buffalo (Bubalus bubalis) embryos

The present study was undertaken to examine the effects of cytoplasmic volume on nucleus reprogramming and developmental competence of buffalo handmade cloning (HMC) embryos. We found that both HMC embryos derived from ~150% cytoplasm or ~225% cytoplasm resulted in a higher blastocyst rate and total cell number of blastocyst in comparison with those from ~75% cytoplasm (25.4 ± 2.0, 27.9 ± 1.6% vs. 17.9 ± 3.1%; 150 ± 10, 169 ± 12 vs. 85 ± 6, P<0.05). Meanwhile, the proportions of nuclear envelope breakdown (NEBD) and premature chromosome condensation (PCC) were also increased in the embryos derived from ~150 or ~225% enucleated cytoplasm compared to those from ~75% cytoplasm. Moreover, HMC embryos derived from ~225% cytoplasm showed a decrease of global DNA methylation from the 2-cell to the 4-cell stage in comparison with those of ~75% cytoplasm (P<0.05). Furthermore, the expression of embryonic genome activation (EGA) relative genes (eIF1A and U2AF) in HMC embryos derived from ~225% cytoplasm at the 8-cell stages was also found to be enhanced compared with that of the ~75% cytoplasm. Two of seven recipients were confirmed to be pregnant following transfer of blastocysts derived from ~225% cytoplasm, and one healthy cloned calf was delivered at the end of the gestation period, whereas no recipients were pregnant after the transfer of blastocysts derived from ~75% cytoplasm. These results indicate that the cytoplasmic volume of recipient oocytes affects donor nucleus reprogramming, and then further accounted for the developmental ability of the reconstructed embryos.

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.

Buffalo embryos produced by handmade cloning from oocytes selected using brilliant cresyl blue staining have better developmental competence and quality and are closer to embryos produced by in vitro fertilization in terms of their epigenetic status and gene expression pattern

We compared handmade cloned (HMC) buffalo blastocysts produced from oocytes stained with Brilliant Cresyl Blue (BCB) and classified into those with blue (BCB+) or colorless cytoplasm (BCB-). The blastocyst rate was higher (p<0.001) for BCB+ than for BCB- oocytes (43.41 ± 2.54 vs. 22.74 ± 1.76%). BCB+ blastocysts had inner cell mass (ICM) cell number, ICM-to-trophectoderm ratio, global level of H3K18ac, apoptotic index, and expression level of BCL-XL, but not that of CASPASE-3, similar to that of blastocysts produced through in vitro fertilization (IVF), which was higher (p<0.05) than that of BCB- blastocysts. The global level of H3K9me2, which was similar in BCB+ and BCB- blastocysts, was higher (p<0.01) than that in IVF blastocysts. The expression level of OCT4 and SOX2 was higher (p<0.05) and that of GATA2 was lower (p<0.05) in BCB+ than that in BCB- blastocysts, whereas that of DNMT1, DNMT3a, NANOG, and CDX2 was not significantly different between the two groups. The expression level of DNMT1, OCT4, NANOG, and SOX2 was lower (p<0.05) and that of CDX2 was higher (p<0.05) in BCB+ than in IVF blastocysts. In conclusion, because BCB+ blastocysts have better developmental competence and are closer to IVF blastocysts in terms of quality, epigenetic status, and gene expression than BCB- blastocysts, BCB staining can be used effectively for selection of developmentally competent oocytes for HMC.

Birth of cloned calves from vitrified-warmed zona-free buffalo (Bubalus bubalis) embryos produced by hand-made cloning

The availability of techniques for the vitrification of cloned blastocysts can improve their effective use. The present study compared the developmental competence of buffalo cloned embryos derived from adult (BAF), newborn (BNF) and fetal fibroblast (BFF) before and after vitrification. Despite similar cleavage rates among the three groups, the blastocyst rate was lower for BAF- than BNF- and BFF-derived embryos (30.2±2.2% vs 41.7±1.7% and 39.1±2.1%, respectively; P<0.01). The total cell number of BNF-derived blastocysts was significantly higher (P<0.01) than that of BFF-derived blastocysts, which, in turn, was higher (P<0.01) than that of BAF-derived blastocysts. Following transfer of vitrified-warmed blastocysts to recipients, no pregnancy was obtained with fresh (n=8) or vitrified-warmed (n=18) BAF-derived blastocysts, whereas transfer of fresh BNF- (n=53) and BFF-derived (n=32) blastocysts resulted in four and three pregnancies, respectively, which aborted within 90 days of gestation. The transfer of vitrified-warmed BNF-derived blastocysts (n=39) resulted in the live birth of a calf weighing 41kg, which is now 23 months old and has no apparent abnormality, whereas the transfer of vitrified-warmed BFF-derived blastocysts (n=18) resulted in one live birth of a calf that died within 6h. These results demonstrate that cloned buffalo embryos cryopreserved by vitrification can be used to obtain live offspring.