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Scientific Method / Science & Exploration

Is this sausage supposed to be green?

Scientists in Taiwan have created a new transgenic pig in this year's must- …

Genetically modified animals are now a huge part of medical research.  Since the 1980s, it has been possible to insert non-native genes (transgenic) or delete genes (knockout) from mice.  Mice are used for a few reasons; they're small and don't eat much, so you can house them fairly inexpensively and they breed quickly so you can have a fairly steady stream of animals.  Image courtesy of the BBC

The benefits for using transgenic or knockout mice are enormous.  For example, deleting the gene that encodes for either the low-density lipoprotein receptor (Ldlr) or for apolipoprotein E (Apoe) results in mice that will develop atherosclerosis, providing a very useful animal model for the disease.  It can be used to elucidate the role of a particular protein in a disease.  This can be useful amongst other cases when you have an inhibitor to an enzyme that is fairly dirty, making it difficult to tease out exactly what pathway is responsible for the effect you are looking for.  By comparing the results to the same model in mice lacking the target gene,  it is possible to confirm that the effect you see is due to inhibition of that pathway.

As mice breed almost as well as rabbits, it is also fairly simple to create double or triple knockouts and transgenics.  One such transgenic mouse that is often crossed onto other lines is the eGFP mouse.  This little critter has been modified to express a modified jellyfish protein, enhanced Green Fluorescent Protein (eGFP).  eGFP is constitutively expressed in all the cells of these mice, although not the fur.  When you shine an ultraviolet light on them, they glow a bright green.  Whilst this might not sound much use, it comes in very handy in studies that involve transplantation of tissues between animals.  If the donor cells come from an eGFP mouse, it is child's play to identify them.  All you need is a fluorescent microscope.  And yes, when you look at the insides of an eGFP mouse, they do have a green tinge.

Critics of using mice in research will often point out that as research animals go, mice aren't really that close to humans, and that higher mammals such as pigs or primates are better*.  To that end, a laboratory in Taiwan has announced the creation of GFP pigs that express the protein in all their cells.  Although green bacon won't be making it's way onto the shelves, the researchers aim to use these green pigs in much the same way as the mice I described above.

Another, less destructive use for eGFP mice, and their cousins that express a red fluorescent protein, could also be for Christmas tree decoration.  Why have ropes of blinking lights when you could ring your tree with a clear habitrail and a UV light source - I know the glowing critters would keep your other household pets entertained for hours!

*Although this is true, the expense of using animals such as pigs, coupled with their much greater intelligence compared to mice thankfully makes their use increasingly unpopular.

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