Epstein--Barr virus-induced cell fusion

Serological and molecular biological studies have shown an association between Epstein--Barr virus (EBV) and nasopharyngeal carcinoma. Although it has been shown that the epithelioid tumour cells carry EBV genomes, they are apparently devoid of receptors for EBV (H.W., unpublished observations). Other have suggested that fusion of EBV carrying cells with epithelial cells may be the mode of entry of the virus into cells unable to absorb the virus and that this may be mediated by one of the known syncytium-forming viruses which inhabit the respiratory tract (for example, members of the paramyxovirus group). de Thé and colleagues suggested that intercellular bridges could be seen in NPC tumour material. We have developed a technique which permits the preparation of stable monolayers of viable human lymphoblastoid cell lines. Using this technique we have now demonstrated that EBV can induce fusion between EBV-superinfected lymphoblastoid cells and cells devoid of EBV receptors.     

细胞融合技术及其进展

自1958年Okada首次表明紫外灭活的仙台病毒可以诱导体外培养细胞融合形成多核体以来。细胞融合技术得到了迅速发展和应用。以聚乙二醇(PEG)为代表的化学融合方法在生物、遗传、医药学等研究领域取得了可喜的成绩。自1978年报道电脉冲诱导细胞融合成功以来．Zimmermann及其同事将细胞电介质电泳引入诱导细胞间接触,创立了物理的实用的Zimmermann电融合法。现在,电融合法已由非特异性的细胞电融合发展为特异性电融合法。激光诱导细胞融合技术成为目前的研究热点．但此项技术尚处于发展初期,有待于进一步完善。本综述了PEG化学融合法．电融合领域的新进展和激光诱导细胞融合技术。     

Nanog promotes transfer of pluripotency after cell fusion

Through cell fusion, embryonic stem (ES) cells can erase the developmental programming of differentiated cell nuclei and impose pluripotency. Molecules that mediate this conversion should be identifiable in ES cells. One candidate is the variant homeodomain protein Nanog, which has the capacity to entrain undifferentiated ES cell propagation. Here we report that in fusions between ES cells and neural stem (NS) cells, increased levels of Nanog stimulate pluripotent gene activation from the somatic cell genome and enable an up to 200-fold increase in the recovery of hybrid colonies, all of which show ES cell characteristics. Nanog also improves hybrid yield when thymocytes or fibroblasts are fused to ES cells; however, fewer colonies are obtained than from ES x NS cell fusions, consistent with a hierarchical susceptibility to reprogramming among somatic cell types. Notably, for NS x ES cell fusions elevated Nanog enables primary hybrids to develop into ES cell colonies with identical frequency to homotypic ES x ES fusion products. This means that in hybrids, increased Nanog is sufficient for the NS cell epigenome to be reset completely to a state of pluripotency. We conclude that Nanog can orchestrate ES cell machinery to instate pluripotency with an efficiency of up to 100% depending on the differentiation status of the somatic cell.     

Transplanted bone marrow regenerates liver by cell fusion

Results from several experimental systems suggest that cells from one tissue type can form other tissue types after transplantation. This could be due to the presence of multipotential or several types of adult stem cells in donor tissues, or alternatively, to fusion of donor and recipient cells. In a model of tyrosinaemia type I, mice with mutations in the fumarylacetoacetate hydrolase gene (Fah-/-) regain normal liver function after transplantation of Fah+/+ bone marrow cells, and form regenerating liver nodules with normal histology that express Fah. Here we show that these hepatic nodules contain more mutant than wild-type Fah alleles, and that their hepatocytes express both donor and host genes, consistent with polyploid genome formation by fusion of host and donor cells. Using bone marrow cells marked with integrated foamy virus vectors that express green fluorescent protein, we identify common proviral junctions in hepatic nodules and haematopoietic cells. We also show that the haematopoietic donor genome adopts a more hepatocyte-specific expression profile after cell fusion, as the wild-type Fah gene was activated and the pan-haematopoietic CD45 marker was no longer expressed.     

Monoclonal antibody production by receptor-mediated electrically induced cell fusion

Fusion of myeloma cells and B lymphocytes to form hybridomas which produce monoclonal antibodies has been a major advance, but the poor efficiency and randomness of viral or polyethylene glycol fusion techniques generally gives poor yields of specific, high affinity antibodies. High voltage electrical fields with dielectrophoresis to ensure cell alignment can fuse a limited number of cells under direct microscopic examination, but it is not possible to identify B-cells destined to secrete relevant antibodies. However, B-cells express, on their surface, antigen receptor immunoglobulins of the same antigenic specificity as the secreted antibodies. Binding of antigen to surface immunoglobulins stimulates proliferation and differentiation of B-cells into plasma cells. Here we report the use of the selective, high affinity interaction of antigen with surface immunoglobulins on B-cells to facilitate a close adherence to myeloma cells. The antigen, covalently conjugated to avidin, binds to the surface immunoglobulins on B-cells. This B-cell-antigen-avidin complex binds to biotin covalently attached to the surface of myeloma cells. An intense electric field across a bulk cell suspension then produces selective fusion of cells in contact, that is, of myeloma cells with B-cells which make the appropriate antibody. We have used this technique with several antigens, and all resultant hybridomas secrete appropriate antibodies with very high affinity.     

属性内-融合与数据融合挖掘

属性融合是潜藏在 P-集合内的一个重要的应用特性,P-集合的动态特性来自 P-集合的属性融合。利用内 P-集合的结构与动态特性,给出属性内-融合概念、结构和定理,最后给出在属性内-融合条件下的数据融合挖掘和数据融合挖掘准则与数据融合挖掘-筛选的应用。     

His-猪生长激素融合基因在Bm-N细胞和蚕体内的表达与纯化

用构建的带有His—Tag pgh融合基因的重组杆状病毒Bm—BacPAK6—pgh研究了Bm—BacPAK6—pgh在家蚕细胞(Bm—N)和蚕体内的表达，并对蚕体表达产物进行了纯化．SDS—PAGE电泳分析显示，重组病毒Bin—BacPAK6—pgh在Bin—N细胞、蚕体中得到了融合表达，Western blot分析表明，Bm—N细胞、蚕体中表达的融合蛋白与大肠杆菌表达的猪生长激素具有相同的抗原性．Bm-BacPAK6-pgh在Bin—N细胞内的表达始于24h，而蚕体中的表达始于72h，二者的表达峰分别在96h和120h．经40％饱和度硫酸铵盐析和Ni—NTA Agarose亲和柱二步纯化可获得SDS—PA(正电泳纯的具有抗原性的重组猪生长激素融合蛋白。     

Bone marrow cells adopt the phenotype of other cells by spontaneous cell fusion

Recent studies have demonstrated that transplanted bone marrow cells can turn into unexpected lineages including myocytes, hepatocytes, neurons and many others. A potential problem, however, is that reports discussing such 'transdifferentiation' in vivo tend to conclude donor origin of transdifferentiated cells on the basis of the existence of donor-specific genes such as Y-chromosome markers. Here we demonstrate that mouse bone marrow cells can fuse spontaneously with embryonic stem cells in culture in vitro that contains interleukin-3. Moreover, spontaneously fused bone marrow cells can subsequently adopt the phenotype of the recipient cells, which, without detailed genetic analysis, might be interpreted as 'dedifferentiation' or transdifferentiation.     

Expression ofChlamydomonas actin-gfp fusion gene in tobacco suspension cell and polymerization of the actin-gfp proteinin vitro

The fusion gene of actin (cDNA ofChlamydomonas reinhardtii) and green fluorescence protein (gfp) had been constructed into two expression vectors which could be expressed inE. coli and tobacco suspension cells BY2. The correct expression was observed inE. coli and BY2 with a fluorescence microscopy. The fusion protein, which took part in the membrane skeleton, was mainly located peripherally along the membrane, specially the fusion protein was distributed around nucleus and cell plate, while the fusion protein also forms F-actin in the cell. The fusion protein was purified from Bl21plus by ammonium sulfate fractionation, ion exchange chromatography and hydrophobic interaction chromatography. The purified production could polymerize into F-actin when the actin polymerizing buffer was added. It was demonstrated that the characteristics and function of actin inChlamydomonas was similar with those of animals and higher plants.     

人M-CSF与SCF融合蛋白的构建及其在昆虫细胞中的表达

应用重组DNA技术构建M-CSF与SCF的融合基因并将其克隆于昆虫杆状病毒转移载体pVL1392中,通过与野生型苜蓿夜蛾核型多角体病毒(AcNPV)DNA共转染草地夜蛾细胞Sf9,融合基因插入AcNPV基因组.重组病毒感染单层Sf9细胞后,表达产物分泌到胞外培养液中,用MTT比色法和TF-1细胞株可检测到表达产物与IL-3的协同效应.上述研究为开发具有应用价值的新型细胞融合因子奠定了基础.     

Induction of light chain expression in a pre-B cell line by fusion to myeloma cells

Pre-B cells, the first cells in the B-lymphocyte differentiation pathway which express immunoglobulin, have recently been shown to express cytoplasmic mu heavy chain (H) but not light chain (L). If, as is believed, pre-B cells are the precursors of immature B lymphocytes, which express surface IgM, the differentiation of pre-B cells to immature B lymphocytes must be accompanied by the expression of light chains. In this case, it should be possible for the progeny of a single pre-B cell to express a variety of light chains in association with the same heavy chain. We have tested this hypothesis by hybridizing a pre-B cell line 18-81 expressing only cytoplasmic mu chains with variant myeloma cells which do not express light chains. Hybridization of B-lymphoma cells with myeloma cells usually produces a hybrid with the phenotype of the more differentiated parent. In this case, the fusion resulted in the induction of light chain expression from the 18-81 genes and we have been able to demonstrate that independent hybrids express different light chains, in accordance with the hypothesis that a pre-B cell committed to expression of a single mu heavy chain can generate progeny expressing different slight chains.