White blood cells — which defend the body from germs — have been used for cloning before, but they have usually been collected from less-than-convenient sources, like bone marrow, the lymph nodes and the liver. In this case, the researchers wanted to find out if they could use cells from a more convenient source — 'peripheral blood', like that taken from a vein in an arm, leg, or in the case of the mouse, the tail.
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The process is the same, no matter where you get the white blood cell from. It's called 'somatic-cell nuclear transfer', and it involves transplanting a white blood cell nucleus — the part that has all the genetic information — into an unfertilized ovum (or egg cell) that has had its nucleus removed. The resulting cell, now with a full set of chromosomes from the white blood cell, will begin to divide, just as if the original ovum was fertilized by a sperm, and the animal that grows from the egg will be genetically identical to the donor.
In the past, criticisms of cloning included that the resulting animals never lived long and they were infertile, and in the case of somatic-cell nuclear transfer, that at least one of the donors had to be euthanized. However, the mouse the researchers cloned from this peripheral blood lived a normal lifespan of 23 months, was fertile throughout its adult life, and the donor only had to 'suffer' through a needle prick to draw some blood.
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With this peripheral blood being a far easier source of white blood cells, and with it causing no more harm to the donor animal than the prick of a needle, this new method offers researchers a very efficient method of cloning. This is very useful for studies that use laboratory mice, especially those involving genetic studies, since having animals that all have the same genetics makes the studies much simpler and the results more trustworthy.
We're likely a ways off from adapting these techniques to cloning other animals, but with these kinds of advances, we might soon be putting terms like 'endangered' and 'critically-endangered' and even 'extinct in the wild' on their own extinction list.
(Photo courtesy: Riken BioResource Center)
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