Cloning: The path to extended youth? |
When Dolly was unveiled three years ago as the first cloned mammal it was as if the new millennium had already dawned. From the pages of pulp fiction and B movies came the clones with an all out media blitz which had pundits opining and Luddites pontificating. On this occasion it seems that the media feeding frenzy was proportionate to the significance of the discovery.
One issue that was of particular interest was whether the age of Dolly's cells would reflect their previous incarnation or did Dolly start with a tabula rasa like any newborn. It was soon determined that Dolly's cells were older than sheep that had been born naturally. It had been hoped that the nuclear transfer cloning technique would be able to provide a limitless supply of cells for regeneration and repair of diseased tissues. The limited lifespan of Dolly's cells were a setback for this goal.
The April 28th, 2000 issue of Science features a report indicating that Dolly's premature frailty is not necessarily the rule when dealing with clones. On the contrary, it appears that clones can actually be younger than naturally born animals. The bearer of this joyous news is an aptly named young calf, Persephone.
The clones in this study were made by a technique that is somewhat distinct from how Dolly was produced. In the diagram of the cell cycle given above, the cells that were used to generate Dolly and Persephone were halted at different stages of the cell cycle. Dolly was produced from cells that had temporarily withdrawn from the cell cycle into a stage referred to as G0 or quiescent phase. Persephone, on the other hand, was produced from a cell that had divided until it could undergo no further DNA replication and encountered a roadblock at the border of G1 and S phase. Persephone's mother cell was considered senescent. This may be the reason that Persephone is younger than she should be and Dolly is older than she should be.
The implications of the experiments with Persephone are enormous. This confirms that it is possible to produce a plentitude of cells through nuclear transfer and somatic cell cloning. These cells can be used to repair tissues that have been damaged by aging or disease. This research has yielded a model system which enables the examination of the role that telomere length plays in aging. It also gives rise to the more controversial possiblities of creating longer-lived human clones. Whatever future developments proceed from this discovery, it is a watershed development in aging research and is particularly pertinent to the telomere theory of aging.
Created May 9th, 2000. Copyright 2000 by Duane Hewitt
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