Drosophilaphilia

The little tiny fruit fly Drosophila melanogaster has been an unlikely help in our understanding of biology. It’s segmented developmental stages have taught us tons about how the body gets built. It has a robust but simplified circadian rhythm available for study. Its basic cell systems have offered up easy targets for biologists hoping to understand the most primitive of pathways. Even though there isn’t that much genetic similarity between us and them (although I can’t find numbers that say how different we are. Can you?), some genes actually are conserved, and can even become drug targets with appropriately directed efforts.

But sometimes, we may get a little carried away. We give them too much credit.

For example, you may be tempted to study cocaine addiction in flies (been done) or alcoholism (been done) or inbreeding (been done) or seizures (been done) or ADHD (been done) or heart disease (been done) or the reasons why men never ask for directions (never been done, but have you ever notices how flies seem to wander?). These kinds of temptations are common, may not yield a lot of useful information.

So how do you push the limits of fruit fly research without going bananas?

Still, the neural system of the fruit fly is complex for being so tiny. If you think about all the things that it has to do, respond to and control, you can see that can live up to their short life. Their nerves operate in exactly the same way a human nerve operates; the neuronal differences between us and them are quantitative and contextual. That being the case, some scientists are pushing the limits of utility to find out what neurons can teach us of our own nervous system.

For example, take the guy who wants to study the effect of brain trauma in Drosophila. Now, brain trauma is an important subject. It is usually studied in rodents using some kind of protocol in which a rat or mouse is thumped the head with some standard weight. Then the brain is examined to see what has happened. You can’t do that in fruit flies. Can you imagine having to give a fruit fly a concussion without completely squishing it? You’d be raising that body count all day.

Marc Freeman of the University of Massachusetts studies the role of glial cells in nerve trauma. Glia constitute the neural entourage. They help and support neurons and allow them to get what they need to do their job. They also help clean up pieces of dead neurons through phagocytosis (think of an amoeba eating a brownie. Same concept.) Freeman wants to study that process in Drosophila, where neurons are sparse and easy to get to. But how do you do that if you can’t crush the head in? Next best thing. They cut off its nose, or rather, one of the olfactory organs that sticks out of the antennae or the mouth. How they do that, I don’t know. They probably need a microscope, six small arm straps and a really small bone saw.

By the way, the reference to how to do that to a fly comes out of the lab of Nobel-winner Richard Axel, in case you’re interested.

Cutting off of the organs causes olfactory axons that project to the brain to die off. All that dead matter, (called the neuron corpse, seriously,) has to be cleaned up. Researchers can go into the brains of post-denosed flies, section the brains (another awful job) and stain them for different markers to see what gets activated when. Manipulation of the model, genetic or otherwise, can allow researchers to figure out the step-by-step process that allows a glial cell to eat a neural corpse.

This works.

So, we can embrace the fly. We just have to have the right attitude. When you’re out there doing a project of your own, stop and think: can I do this to Drosophila? You might be surprised. And if you don’t have a scientific use for it, maybe you can at least use the name. Don’t you think that would be a pretty name for a baby girl? Something like Drosophila Marie Johnson? You could call her Drosy for short!

For references:
See McDonald et al. “The Drosophila cell corpse engulfment receptor Draper mediates glial clearance of severed axons. Neuron. 2006;50:869–881. 2006.

Or just, you know, PubMed or Google “drosophila” and your disease of choice.