Previous studies have shown that proline mutations in the heptad repeat region stabilize the coronavirus spike (S) protein in a pre-fusion state. To understand the impact of proline substitutions on the fusogenicity of the S protein, we engineered the swine acute diarrhea syndrome coronavirus (SADS-CoV) S protein with two proline substitutions (S-PP) and examined its fusogenicity using dual-split-protein based cell-cell fusion assay. Unlike the wild-type S (S-WT), S-PP rarely formed syncytia. Additionally, protein expression of S-PP was impaired compared to S-WT, as previously reported. Our results indicate that pre-fusion stabilized S protein is unable to induce membrane fusion and provide a better understanding of SADS-CoV S and vaccine antigen design.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein mediates virus entry by binding to the host cell receptor, human angiotensin converting enzyme 2 (hACE2), and catalyzing virus–host membrane fusion. The S protein also mediates cell–cell fusion, potentially allowing the virus to spread virion-independently. Here, we compared the fusogenicity of SARS-CoV-2 variant S proteins using a cell–cell fusion assay. In cells overexpressing hACE2, cell–cell fusion ability of all tested SARS-CoV-2 variants was similar to that of the Wuhan-Hu-1 strain. However, in cells with endogenous hACE2, SARS-CoV-2 variants, especially the Delta variant, stimulated significantly greater cell–cell fusion than the original strain. Our results showed that the Delta variant S protein is highly fusogenic and can spread rapidly by utilizing small amounts of hACE2.

Although there are several methods for establishment of stem cell line, most of them has critical limit such as, ethical problem and infectious concern. Accordingly, we investigated the cell fusion technique as a new tool to establish a stem cell line. We cultured mouse embryonic stem cell (ESC) and somatic cells. Then, these two type cells were fused by electro cell fusion that consist of three steps (AC→DC→AC). The fused cells were individually transferred into a 96-well plate and cultured in ESC culture medium for 6 ~ 7 days. Newly formed colonies were evaluated several analysis methods like morphology, alkaline phosphatase (AP) activities, expression of pluripotency marker genes and proteins, and karyotyping. The fusion efficiency from the ESC and somatic cell into colony formation was about 0.3 ~ 0.5 %. The electro cell fused (EF) new stem cell colonies (EF-SC1 ~ 4) were indicated normally round-shape morphology similarly to ESC colonies and each colonies were expressed green fluorescent protein that having somatic cells. Also, all EF-SC groups were highly expressed AP activity and pluripotency marker proteins, POU5f1, NANOG, SOX-2 and SSEA-1. In the transcription levels, all EF-SC groups were significantly higher level of expression in Pou5f1 and Nanog compared to donor cells (ESC and somatic cell) (p<0.05). In particular, the level of Pou5f1 expression was about 2-folds higher in EF-SC2 and EF-SC3 groups than in control and EF-SC1 groups (p<0.05). Also, the level of Nanog expression was very significantly higher in EF-SC2 group (3.5-folds) compared to control ESC group, and the expression levels among treatment groups were variable (ESC<EF-SC1<EF-SC4<EF-SC3<EF-SC2, p<0.05). In karyotype analysis, the results of EF-SC2 and EF-SC3 were presented the same that of ESC, while that of EF-SC1 and EF-SC4 shown aneuploid mutation in chromosome 8. Taken together, these results demonstrate that electro cell fusion technique can be used as a new method to establish of stem cell lines.

본 연구에서는 체세포를 이용한 돼지 복제수정란의 생산효율을 높이는 최적의 방법을 구명코자 핵이식 수정란에 각기 다른 조건들의 전기적 자극에 의한 융합과 활성화를 유도하여 융합율, 분할율, 후기배로의 발달율 및 배반포기배의 할구수를 비교ㆍ조사하여 다음과 같은 결과를 얻었다. 핵이식 복제 수정란과 전기자극에 의한 단위발생란과의 체외배양후 분할율을 비교한 결과 두 처리간에 유의적인 차이를 나타내지 않았으나, 배양7일째 배반포기배로의 발달율에 있어서는 복제수정

복제수정란 생산에 있어서 수핵란 내 체세포 주입 후 전기적인 융합은 필수과정인데, 이 과정을 거치는 동안 많은 수의 체세포 주입 난자가 융합에 실패하거나 lysis가 일어나게 된다. 본 실험에서는 한우 체세포를 이용하여 핵이식을 실시한 후 수핵세포질과 응합을 시도할 때 전기융합 방법에 따른 융합율과 배발달율을 검토하고자 실시하였다. 공여세포는 한우 귀 세포조직을 채취하여 0.05% trypsin과 EDTA가 첨가된 D-PBS로 세포를 분리한 후 DMEM

칡소의 귀세포를 이용한 핵이식 시에 전기 융합조건이 핵이식란의 발생에 미치는 영향을 알아보고, 칡소의 귀세포와 한우의 태아섬유아세포를 이용한 핵이식란을 이식하여 수태율을 비교하였다. 전기자극 조건에 따른 핵이식 후 융합율은 51∼68%의 범위로 차이는 없었으나, lysis 율은 1.9kv/cm의 10us, 20us에서 각각 0.0과 38.7%, 2.0kv/cm의 10us, 20us에서 각각 2.9와 37.5%, 2.1kv/cm의 10us, 20us에서 각각 21.2와 51.8%을 보였다. 난할율은 1.9kv/cm의 10us, 20us에서 각각 75.8과 69.8%, 2.0kv/cm의 10us, 20us에서 각각 76.9와 68.8%, 2.1kv/cm의 10us, 20us에서 각각 70.5와 68.5로 큰 차이가 없었다. 그러나 배반포 발생율은 1.9kv/cm의 10us, 20us 각각 19.5와 48.6%, 2.0kv/cm의 10us, 20us에서 각각 20.0과 40.9%, 2.1kv/cm의 10us, 20us에서 각각 44.2와 27.0%로 각 조건에서 시간에 따른 차이를 보였다. 핵이식에서 공여세포와 세포질간의 융합율과 lysis율은 전압과 통전시간에 영향을 받으며 전압을 높이는 것이 통전시간을 길게 하는 경우보다 수핵난자의 세포질에 상해를 줄이고 배반포 발생에 유리 하였다. 한우의 태아섬유아세포의 핵이식후 생산된 배반포를 5마리의 수란우에 이식한 결과 두 마리가 임신되었고(40.0%), 칡소의 귀 세포를 핵이식한 후 생산된 배반포를 19마리에 이식한 결과 3마리가 임신되었다(15.8%).

The present study was performed to evaluate the best electric fusion condition in nuclear transfer, Korean Native Cattle fibroblasts were used as nucleic donors. Oocytes from slaughterhouse were matured in vitro for 22 h and enucleated. Each individual cells were transferred into enucleated ocytes and reconstructed embryo were placed into the fusion chamber. In experiment 1, pulse were performed by altering pulse duration at 1. 75kv/cm, 1 time. When pulse duration is 30, fusion and development rates is higher than other conditions. In experiment 2, the effect of different pulse number were studied at the pulse duration 30 and the same pulse intensity. When pulse number was one, fusion rates were higher than other conditions. The fused embryos were moved to culture medium and assessed their development to blastocyst. These results showed that best fusion condition was 30 and one time. And the fibroblasts derived from Han Woo can be reprogrammed by nuclear transplantation and develop subsequently in vitro.

The objectives of the present study were improvements in the efficiency of developmental rates to morula and blastocyst stages to produce a large number of genetically identical nuclear transplant embryos. The oocytes collected from slaughterhouse ovaries were matured for 24 h and then enucleated and cultured to allow cytoplasmic maturation and gain activation competence. And then the donor embryos were treated for 12 h with 10 g /ml nocodazole and 7.5 g /ml cytochalasin B to synchronize the cell cycle stage at 26 h after the onset of culture. The blastomeres were transferred into the perivitelline space of the enucleated nocytes and blastomeres and oocytes were fused by electrofusion. The cloned embryos were then cultured in various conditions to allow further development. The age of the recipient(30 vs 40 h) had no significant effect on the fusion rates(82.4 vs 82.1%) and the developmental rates to morula /blastocyst(9.8 vs 11.0%). Effect of Nocodazole treatment on the donor cell cyle synchronization to improve the developmental rates of bovine nuclear transplant embryos was significantly higher than control group(21.4 vs 10.1%, p<0.05). Significant differences were in the percentage of fusion rates(72.9,77.1vs 61.9%) in three types of fusion medium(PBS(+), mannitol and sucrose, p<0.01). The developmental rates of bovine nuclear transplant embryos appeared to be highest in mSOF medium under 5% 0 condition, but no significant differences were found when compared with TCM199-BOEC and mSOF under two different oxygen ratio(5 and 20%).

This study was to investigate an effective biological control of forage diseases and provide a basic data and a model in improving variety of antagonistic bacteria, with growth promoting effect on forage, through cell fusion. The results obtained were sum

식물원형질체를 이용하여 체세포잡종을 육성하기 기초자료를 얻고자 식물의 엽육부위, Callus에서 효과적인 원형질체의 분리, 적합한 배양조건 및 세포융합에 관한 조건을 조사한 결과를 요약하면 다음과 같다. 1. 배양 융합조건에 적합한 식물원형질체의 분리 방법은 여러 종류의 효소농도에 따라 다르지만 담배 및 완두엽육 원형질체분리에는 Macerozyme 0.5%, Cellulase 2.0%, KDS 0.5%, Mannitol 0.7M의 효소용액에 처리시 활성 있는 원형질체를 얻을 수 있었다. 2. 배양중인 담배 및 대두의 Callus로부터 원형질체분리는 배양기간에 따라 세포활성도가 떨어지거나 쉽게 파괴되는 현상을 보여 양호한 원형질체를 얻을 수가 없었다. 3. 원형질체의 배양은 배양배지에 Plating할 경우 세포농도에 따라 차이가 있었으며 1.0 104 /ml이상이어야 분열이 가능하였고 배양조건은 150Lux 12시간 광암처리후가 세포분열 및 증식이 가장 왕성하였다. 4. 세포융합은 PEG농도가 중요하며 PEG 1500 0.33M에서 CaCl2농도가 높을수록 융합율이 증가되는 경향이었다.