Tuesday, 28 October 2008

Down syndrome research pop quiz: fruit flies 94, Sarah Palin zilch

This story has already been covered to death (or at least I hope so) on teh interwebs, but I must have my say. You see, when Palin dissed fruit flies...

...she didn't just diss fruit flies and the general and specific importance of model organism research (for which she is rightly and expertly skewered by Christopher Hitchens, Kevin Berger and others). She also dissed me.

As mentioned previously here and here, I did my PhD research on the fruit fly* Drosophila melanogaster. Specifically, I worked my butt off for six years to understand some of the myriad and complex functions of a fruit fly gene called Ras (the human counterpart of which plays a role in the onset and/or development of almost every kind of cancer) on the ovarian and embryonic development of the fruit fly, and how this has been modulated during fruit fly evolution.

That's right, friends, I am officially (and, it must be said, very proudly) on Sarah Palin's shit list: not only did I do research on fruit flies (booooo!) but I also did research on evolution (hissssss!).

But enough about me.

Almost unbelievably, Palin's sneer came directly on the heels of her own call to help families with special needs kids like her nephew with autism and her son with Down syndrome. See, in Palin's (surprisingly young) universe, it cannot possibly be fathomed that something as obscure as a fruit fly could help special needs kids. But a quick search on PubMed for 'Drosophila and "Down syndrome"' yields 94 peer-reviewed research articles including this one [my emphases]:

Dscam guides embryonic axons by Netrin-dependent and -independent functions.

Andrews GL, Tanglao S, Farmer WT, Morin S, Brotman S, Berberoglu MA, Price H, Fernandez GC, Mastick GS, Charron F, Kidd T.

Development. 2008 Oct 23. [Epub ahead of print]

Developing axons are attracted to the CNS midline by Netrin proteins and other as yet unidentified signals. Netrin signals are transduced in part by Frazzled (Fra)/DCC receptors. Genetic analysis in Drosophila indicates that additional unidentified receptors are needed to mediate the attractive response to Netrin. Analysis of Bolwig's nerve reveals that Netrin mutants have a similar phenotype to Down Syndrome Cell Adhesion Molecule (Dscam) mutants. Netrin and Dscam mutants display dose sensitive interactions, suggesting that Dscam could act as a Netrin receptor. We show using cell overlay assays that Netrin binds to fly and vertebrate Dscam, and that Dscam binds Netrin with the same affinity as DCC. At the CNS midline, we find that Dscam and its paralog Dscam3 act redundantly to promote midline crossing. Simultaneous genetic knockout of the two Dscam genes and the Netrin receptor fra produces a midline crossing defect that is stronger than the removal of Netrin proteins, suggesting that Dscam proteins also function in a pathway parallel to Netrins. Additionally, overexpression of Dscam in axons that do not normally cross the midline is able to induce ectopic midline crossing, consistent with an attractive receptor function. Our results support the model that Dscam proteins function as attractive receptors for Netrin and also act in parallel to Frazzled/DCC. Furthermore, the results suggest that Dscam proteins have the ability to respond to multiple ligands and act as receptors for an unidentified midline attractive cue. These functions in axon guidance have implications for the pathogenesis of Down Syndrome.

In other words, research on fruit flies is helping us to understand Down Syndrome better. The same can be said for almost all human biology, both pathogenic and 'normal' (whatever that means).

And here's where Palin's mocking is even more resonant: the reason fruit fly biology illuminates human biology is because our genomes are so similar and the reason our genomes are so similar is because we inherited them from the last common ancestor of humans and fruit flies [cue Sarah Palin's head popping off and steam shooting out].

*Though not technically correct, 'fruit fly' is the colloquial name for the monumentally important model organism Drosophila melanogaster. True fruit flies belong to the insect family Tephritidae and it was in fact a research project on these Tephritid flies that Palin was so gleefully skewering as wasteful earmark spending. Some have argued that this fact exonerates Palin-- i.e. that she was not mocking D. melanogaster research because she knows how important that is (right, as if Palin knows the difference between true fruit flies and model organism 'fruit flies') but rather she was mocking Tephritid fruit fly research. Problem is that the project she mocked is more applied to human benefit (in this case agricultural productivity) than most D. melanogaster research, not less, so there's that argument out the window.

1 comment:

Rubén Nieto said...

Your post is really brilliant. I like it so much!