Thursday, April 16, 2009

Chimeras, Immunology and other Bad Science on Fringe

Creative taxidermists have been known to assemble monstrous creatures using parts from a variety of animals. It's like the assembly of Frankenstein's monster using the heads, bodies, wings and tails of different species. Such critters are dead, of course, but wouldn't they be horrible if they were alive and crawling about in the sewers?

That's was the basic premise behind this week's episode of Fringe. A monster with the head of a bat, body of a gila monster, and egg-laying system of a wasp escapes from a laboratory and terrorizes the Boston metro area. But this being Fringe, the creature wasn't created by cutting and sewing, since that isn't Science! No, it was genetically engineered, of course.

Now the episode itself was pretty predictable. The monster roams about attacking people and occasionally laying eggs inside its victims. Agent Dunham and super-scientist Walter Bishop must catch it and figure out how to kill its offspring before they burst from poor Agent Francis's gut. Amazingly, they are able to do that, even though Bishop displays a complete lack of understanding of vertebrate genetics, immunology and behavior. The biology was very bad, oh so very bad.

The first problem is that genetic engineering is not like taxidermy. There is no "head gene" that could be introduced into a lizard genome and end up adding hairy big-eared head of a bat to a scaly lizard body. The development of the body plan of animals - both vertebrates and invertebrates - is controlled by the Hox genes, which regulate gene expression during embryonic development. Changes in the regulation and expression patterns of Hox genes are thought to have been a major factor in the evolution of different body plans. And it's not a simple matter of bat Hox proteins functioning differently from lizard Hox proteins - they function similarly even in animals as evolutionarily distant as fruit flies and chickens . Adding a bat's head to a lizard's body would require some very complex engineering of the DNA sequences that regulate gene expression. Add to that the problem that the physiology of a warm-blooded mammal like a bat is very different from a cold-blooded lizard, and it's extrodinarily unlikely that one could engineer a hybrid of the two critters that looks like a fusion of the two. Add on parts of an invertebrate wasp, and it's pretty much complete fantasy.

But despite the implausibility, that didn't really bother me that much. I figure it's dramatic license that allows a visual representation of a hybrid creature.

What bugged me was Dr. Bishop pontificating on the monster's immune system. He confidently claims that bat genes were included in the mix because the bat's special immune system would prevent "massive rejection" of tissue, such as one sees when organ transplants are made. The trouble is that the immune system doesn't work that way. It's one of those little factlets that sounds plausibly sciency if you aren't familiar with the topic, but actually takes a couple of true bits of information and puts them together in a way that is is simply wrong.

It is true that when organs are tranplanted - expecially xenotransplants from different species - they are often seen as foreign tissue and rejected by the immune system. If you created a chimeric creature by sewing together bits and pieces of different animals, tissue rejection would indeed be a problem. But the monster developed from a transgenic embryo. As the immune system develops, it "learns" not to respond to the body's own cells and other molecules. Self-tolerance is one of the characteristics of a normally-functioning immune system, no matter how many different sources of the organism's genes. The monster's bat genes were apparently largely for show - and to provide it with "maternal instincts", of course.

Of course the show is silly on many levels, not the least of which is that crazy Dr. Bishop is supposed to be an expert in chemistry, medicine, genetics and esoteric physics. I guess he doesn't really know everything.

If you are in the US, you can watch the latest episode of Fringe at Hulu.com or in the embedded video below.


Image (top): The mythical Chimera, with the body of a lioness, snake for a tail and an extra goat's head on its back.
Image (bottom): The monster on Fringe.
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2 comments:

Arvind Mishra said...

Very interesting and thought provoking !

eleazar said...

Another example of extreme zoological cluelessness in this episode was frequently referring to the act of implanting the parasitic offspring as "mating" and the hosts as being "pregnant".