Cell fusion

Cell fusion is an important cellular process in which several uninuclear cells (cells with a single nucleus) combine to form a multinuclear cell, known as a syncytium. Cell fusion occurs during differentiation of muscle, bone and trophoblast cells, during embryogenesis, and during morphogenesis. Cell fusion is a necessary event in the maturation of cells so that they maintain their specific functions throughout growth.

In 1847 Theodore Schwann expanded upon the theory that all living organisms are composed of cells when he added to it that discrete cells are the basis of life. Schwann observed that in certain cells the walls and cavities of the cells coalesce together. It was this observation that provided the first hint that cells fuse. It was not until 1960 that cell biologists deliberately fused cells for the first time. To fuse the cells, biologists combined isolated mouse cells, with the same kind of tissue, and induced fusion of their outer membrane using the Sendai virus (a respiratory virus in mice). Each of the fused hybrid cells contained a single nucleus with chromosomes from both fusion partners. Synkaryon became the name of this type of cell combined with a nucleus. In the late 1960s biologists successfully fused cells of different types and from different species. The hybrid products of these fusions, heterokaryon, were hybrids that maintained two or more separate nuclei. This work was headed by Henry Harris at the University of Oxford and Nils Ringertz from Sweden's Karolinska Institute. These two men are responsible for reviving the interest of cell fusion. The hybrid cells interested biologists in the area of how different kinds of cytoplasm affect different kinds of nuclei. The work conducted by Henry and Nils showed that proteins from one gene fusion affect gene expression in the other partner's nucleus, and vice versa. These hybrid cells that were created were considered forced exceptions to normal cellular integrity and it was not until 2002 that the possibility of cell fusion between cells of different types may have a real function in mammals.

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