• Journal of Embryo Transfer
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• v.33 no.4
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• pp.229-235
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• 2018

Polo-like kinase 1 (Plk1) has been known to be a critical element in cell division including centrosome maturation, cytokinesis and spindle formation in somatic, cancer, and mammalian embryonic cells. In particular, Plk1 is highly expressed in cancer cells. Plk1 inhibitors, such as BI2536, have been widely used to prevent cell division as an anticancer drug. In this study, the fertilized murine oocytes were treated with BI2536 for 30 min after recovery from the oviduct to investigate the effect of down-regulation of Plk1 in the in vivo-fertilized murine embryos. Then, the localization and expression of Plk1 was observed by immunofluorescence staining. The sperm which had entered into the oocyte cytoplasm did not form male pronuclei in BI2536-treated oocytes. The BI2536-treated oocytes showed significantly lower expression of Plk1 than non-treated control group. In addition, alpha-tubulin and Plk1 gathered around sperm head in non-treated oocytes, while BI2536-treated oocytes did not show this phenomenon. The present study demonstrates that the Plk1 inhibitor, BI2536, hinders fertilization by inhibiting the formation of murine male pronucleus.

• Proceedings of the KSAR Conference
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• 2001.10a
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• pp.56-56
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• 2001

This study was carried out to investigate on the improvement of fertilizing and developing ability of in vitro matured oocytes from individuals of bulls, sperm type, pretreatment of sperm or oocytes obtained by intracytoplasmic sperm injection(ICSI). 1. The male pronuclear formation and developmental rates of oocytes obtained by ICSI treated individual of bulls were 73.9%-87.0% and 33.3%-60.9%, respectively. 2. The male pronuclear formation and developmental rates of oocytes obtained by ICSI treated fresh and frozen sperm, tail-cutting and tail-scoring sperm were 82.0%, 78.0%, 42.2%, 51.1% and 56.0%, 42.0%, 17.8%, 22.2% respectively. and these values of fresh sperm injection were higher than that of frozen sperm, tail-cutting and tail-scoring. 3. The male pronuclear formation and developmental rates of oocytes obtained by sperm pretreated heparin, BFF(bovine follicula fluid), His, Ca Ionophore(Ⅰ) and Ⅰ ＋ caffeine methods were 66.7%-82.2% and 33.3%-60.6%, respectively. and these values of treatment of Ⅰ＋ caffeine were higher than that of other methods. 4. The male pronuclear formation and developmental rates of oocytes obtained by ICSI treated with or without zona pellucida were 80.0%, 72.0% and 46.0%, 36.0%, respectively.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.1
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• pp.107-112
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• 2005

A high environmental temperature affects the economic performance of pigs. Heat shock protein 70 (HSP70) has been reported to participate importantly in thermotolerance. This study aims to produce transgenic pigs overexpressing porcine HSP70.2, the highly inducible one of HSP70 members, and to prove the cellular thermotolerance in the primary fibroblasts from the transgenics. A recombinant plasmid in which the sequence that encodes the porcine HSP70.2 gene is fused to green fluorescence protein (GFP) was constructed under the control of cytomegalovirus (CMV) enhancer and promoter. Two transgenic pigs were produced by microinjecting pCMV-HSP70-GFP DNA into the pronucleus of fertilized eggs. Immunoblot assay revealed the varied overexpression level (6.4% and 1.4%) of HSP70-GFP in transgenic pigs. After heating at $45^{\circ}C$ for 3 h, the survival rate (78.1%) of the primary fibroblast cells from the highly expressing transgenic pig exceeded that from the non-transgenic pig (62.9%). This result showed that primary fibroblasts overexpressing HSP70-GFP confer cell thermotolerance. We suggest that transgenic pigs overexpressing HSP70 might improve their thermotolerance in summer and therefore reduce the economic loss in animal production.

• Asian-Australasian Journal of Animal Sciences
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• v.21 no.5
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• pp.745-753
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• 2008

Gene-manipulated mice were discovered for the first time about a quarter century ago. Since then, numerous sophisticated technologies have been developed and applied to answer key questions about the fundamental roles of the genes of interest. Functional genomics can be characterized into gain-of-function and loss-of-function, which are called transgenic and knock-out studies, respectively. To make transgenic mice, the most widely used technique is the microinjection of transgene-containing vectors into the embryonic pronucleus. However, there are critical drawbacks: namely position effects, integration of unknown copies of a foreign gene, and instability of the foreign DNA within the host genome. To overcome these problems, the ROSA26 locus was used for the knock-in site of a transgene. Usage of this locus is discussed for the gain of function study as well as for several brilliant approaches such as conditional/inducible transgenic system, reproducible/inducible knockdown system, specific cell ablation by Cre-mediated expression of DTA, Cre-ERTM mice as a useful tool for temporal gene regulation, MORE mice as a germ line delete and site specific recombinase system. Techniques to make null mutant mice include complicated steps: vector design and construction, colony selection of embryonic stem (ES) cells, production of chimera mice, confirmation of germ line transmission, and so forth. It is tedious and labor intensive work and difficult to approach. Thus, it is not readily accessible by most researchers. In order to overcome such limitations, technical breakthroughs such as reporter knock-in and gene knock-out system, production of homozygous mutant ES cells from a single targeting vector, and production of mutant mice from tetraploid embryos are developed. With these upcoming progresses, it is important to consider how we could develop these systems further and expand to other animal models such as pigs and monkeys that have more physiological similarities to humans.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.2
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• pp.178-188
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• 2013

The glycosaminoglycans (GAGs) present in the female reproductive tract promote sperm capacitation. When bovine sperm were exposed to 10 ${\mu}g/ml$ of one of four GAGs (Chondroitin sulfate, CS; Dermatan sulfate, DS; Hyaluronic acid, HA; Heparin, HP) for 5 h, the total motility (TM), straight-line velocity (VSL), and curvilinear velocity (VCL) were higher in the HP- or HA-treated sperm, relative to control and CS- or DS-treated sperm. HP and HA treatments increased the levels of capacitated and acrosome-reacted sperm over time, compared to other treatment groups (p<0.05). In addition, sperm exposed to HP or HA for 1 h before IVF exhibited significantly improved fertilizing ability, as assessed by 2 pronucleus (PN) formation and cleavage rates at d 2. Exposure to these GAGs also enhanced in vitro embryo development rates and embryo quality, and increased the ICM and total blastocyst cell numbers at d 8 after IVF (p<0.05). A real-time PCR analysis showed that the expression levels of pluripotency (Oct 4), cell growth (Glut 5), and anti-apoptosis (Bax inhibitor) genes were significantly higher in embryos derived from HA- or HP-treated sperm than in control or other treatment groups, while pro-apoptotic gene expression (caspase-3) was significantly lower in all GAG treatment groups (p<0.05). These results demonstrated that exposure of bovine sperm to HP or HA positively correlates with in vitro fertilizing ability, in vitro embryo developmental potential, and embryonic gene expression.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.1
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• pp.22-27
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• 1999

Bovine oocytes with compact and complete cumulus cells were cultured in 6 groups for up to 24h in TCM199 buffered with 25 mmol/1 HEPES and supplemented with 10% FCS, 1 mg/ml $17{\beta}$-estradiol, 20 IU/ml hCG. Half of the oocytes at each group cultured in the presence of $25{\mu}g/ml$ cycloheximide at different times during maturation (0, 6, 12, 18, 20, 22 h) were fixed at 24 h of maturation to examine the nuclear progression. The rests of them were inseminated with frozen-thawed spermatozoa in medium BO with 10 mg/ml BSA and 10 mg/ml heparin and fixed after additional 18-20 h culture to evaluate the sperm head transformation. When a protein synthesis inhibitor was added at the onset of the maturation, the oocytes were prevented to proceed GVBD. A few of the oocytes (16%) were able to be penetrated and sperm head decondensation was inhibited either. Addition of cycloheximide after 6-12 h of culture resulted in an increasing percentage of GVBCD (more than 80%), but the oocytes became arrested in M-I (69.2%). More than half of the oocytes was penetrated with a decondensing sperm head. Formation of male pronucleus was first obtained at 12 h of culture in the presence of cycloheximide. When cycloheximide was added from 18 h of culture onwards, nuclear progression to M-II was increasingly restored (80.4-85.5%). The proportion of male and female pronuclear formation increased from 17.9% to 46.2%. It is concluded that protein synthesis is necessary not only for GVBD and development from M-I to M-II, but also for sperm head decendensation and male pronuclear formation in bovine oocytes.

• Korean Journal of Animal Reproduction
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• v.20 no.4
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• pp.413-421
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• 1997

In vitro culture has provided new information on the mechanisms involved in fertilization how sperm and oocyte fuse together. At the same time, results obtained in vitro have led to new questions. Techniques for In vitro maturation of porcine oocytes have progressed such that the problem of the low rate of pronucleus formation with in vitro matured oocytes after in vitro fertilization has been nearly improved. On the other hand, porcine spermatozoa have been shown to be capacitated if the fertilization medium contains caffeine and Ca$^2+$, but the incidence of polyspermy in IVM-IVF oocytes is still high. To prevent polyspermy, co-culture with oviductal cells, sperm preincubation with porcine follicular fluid or control of sperm concentration, have been examined with significant effects but still remarkably high rates of polyspermy. The under standing of these influences is a prerequisite to enhancing in vitro production of porcine em bryos.

• Proceedings of the KSAR Conference
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• 2000.10a
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• pp.7-8
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• 2000

Transgenic animals are very useful for scientific, pharmaceutical, and agricultural purposes. In livestock, transgenic technology has been used forthe genetic alteration of farm animals, the production of human proteins inlarge quantities in the milk of transgenic farm animals, and the generation of animals with organs suitable for xenotransplantation. To date, the transfer of foreign genes into farm animals has been performed mainly by microinjection of DNA into the pronuclei of fertilized eggs. However, the overall success rate of transgenic animals in livestock so far has been disappointingly low, eg., the efficiency is 0∼5% in swine, and less than 1% in sheep and cattle, compared with the rate in mice where 5% microinjected develop into transgenic animals. Recently, McGreath et al. (2000) have succeeded in producing the gene targeted sheep by the use of nuclear transfer from cultured somatic cells transfected with a foreign gene in vitro. However, we may need plenty of time until currently employ this method for gene transfer to farm animals. We have been studying to exploit the method for improving production efficiencies of transgenic animals with emphasis of its application to farm animals. The present paper describes three approaches that we have made in our laboratory to improve production efficiencies of transgenic animals, based on the DNA microinjection method. 1. Co-injection of restriction enzyme with foreign DNA into the pronucleus for elevating production efficiencies of transgenic animals. 2. Efficient selection of transgenic mouse embryos using EGFP as a marker gene. 3. Phenotypes of tansgenic mice expressing WAP/hGH-CAG/EGFP fusion gene produced by selecting transgenic embryos. 4. Efficient site-specific integration of the transgene targeting an endogenous lox like site in early mouse embryos.

• Reproductive and Developmental Biology
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• v.35 no.1
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• pp.105-113
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• 2011

The present study investigated the nuclear remodeling, development potential with telomerase activity and transcription level of X-linked genes (ANT3, HPRT, MeCP2, RPS4X, XIAP, XIST and ZFX) in the bovine somatic cell nuclear transfer (SCNT) embryos using two different fusion and activation methods. Female adult fibroblasts were injected into perivitelline space of in vitro matured oocytes. The oocyte-nucleus complexes were fused and followed by immediately either activated (Group 1), or activated at 1 h post-fusion (hpf) (Group 2), respectively. The incidence of normal premature chromosome condensation (PCC) at 1 hpf was slightly increased in the Group 2, compared to those of Group 1, but there was no significant (p<0.05) difference. The incidence of normal pronucleus (PN) and chromosome spread at 5 and 18 hpf were significantly (p<0.05) higher in the Group 2 than those of Group 1. The cleavage rate to 2-cell stage, developmental rate to blastocyst stage, and the mean number of total and ICM cell numbers were significantly (p<0.05) higher in the Group 2, compared to those of Group 1. Level of telomerase activity was significantly (p<0.05) higher in the SCNT blastocysts of Group 2, compared to those of Group 1. Transcript levels of HPRT, MeCP2 and XIST were not significantly (p<0.05) different between blastocysts of Group 1 and 2. However, transcript level of ANT3, RPS4X, XIAP and ZFX were significantly (p<0.05) up-regulated in the SCNT blastocysts of Group 2, compared to those of Group 1. Taken together, it is concluded that oocyte activation at 1 hpf induces the enhanced developmental potential by efficient nuclear remodeling and subsequent facilitation of the nuclear reprogramming of bovine SCNT embryos.

• Korean Journal of Animal Reproduction
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• v.27 no.4
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• pp.309-315
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• 2003

DNA methylation at CpG sites, which is a epigenetic modification, is associated with gene expression without change of DNA sequences. During early mouse embryogenesis, dynamic changes of DNA methylation occur. In this study, DNA methylation patterns of porcine embryos produced in vivo and in vitro were examined at various developmental stages by the immunocytochemical staining method. Interestingly, active demethylation was not observed on the paternal pronucleus of porcine zygotes. However, differences were detected in the passive demethylation process between in vivo and in vitro embryos. There was no change in the DNA methylation state until the blastocyst stage of in vivo embryos, whereas partial demethylation was observed in several blastomeres from a 4 cell stage to a morula stage of in vitro embryos. The whole genome of inner cell mass (ICM) and trophectoderm (TE) cells in porcine blastocysts were evenly methylated without de novo methylation. Our findings demonstrate that genome-wide demethylation does not occur in pig embryos during preimplantation development unlike murine and bovine embryos. It indicates that the machinery regulating epigenetic reprogramming may be different between species.