This article was automatically translated from Japanese using AI. The Japanese version is the authoritative version.
What is a model organism?
When you think of animals used in research, mice and guinea pigs probably come to mind.
The usual picture is that a drug’s efficacy or structure is tested in these animals first, and only then does the work move on to clinical trials.
That picture isn’t wrong, but there are many other organisms used in research.
Medaka, zebrafish, nematodes, E. coli, yeast, Drosophila melanogaster, Xenopus laevis, Arabidopsis thaliana, silkworms, and so on…
These organisms are called model organisms, and a huge variety of research is carried out with them.
A model organism is one that the research community studies exhaustively, so that by coming to know that single organism inside and out, we can understand features and principles shared with other organisms.
What is Drosophila melanogaster?
Some of the organisms on that list may come as a surprise, but Drosophila melanogaster is probably the most unexpected of all.
Wait, a fly? The kind that shows up in your kitchen?
Exactly!
The scientific name of the fruit fly is Drosophila melanogaster.
It has been central to research recognized by several Nobel Prizes and is used widely across biology.
Fly researchers gather at meetings such as the Japanese Drosophila Research Conference (JDRC), and there are also fly conferences in the Americas, Europe, and Asia. On top of that, meetings focused specifically on the fly nervous system, such as NeuroFly and Neurobiology of Drosophila, show just how global this research community is.
The advantages of working with flies include:
・They have a central nervous system
・A rich toolkit of genetic techniques
・The existence of balancer chromosomes
・A short generation time
・They are easy to rear
・They show stereotyped behavioral patterns
and many more. Because researchers around the world have converged on Drosophila melanogaster, enormous databases have been built, and in the brain nearly the entire network of connections between neurons is now known.
At this point you might wonder whether there is anything left to study. It’s true that we know the wiring, but in many cases we still don’t know what functions that wiring serves.
Beyond that, in areas such as immunity and developmental patterning, there remain a great many open questions, including which molecules are involved.
You might ask what all this effort is for. The answer is that it is precisely by going this far that we can uncover principles universal to living things!
That is what a model organism is for.
And these mechanisms can be applied to drug development, safe genetic engineering, and more.
A brief history of Drosophila research
The story goes that it all began in 1901, when a well-known figure (Charles W. Woodworth) suggested the fly to another researcher (William Ernest Castle) as material for genetics.
The reason: it is easy to rear in large numbers.
Thomas Hunt Morgan later became famous for his genetic studies using Drosophila. His discovery of mutants and his demonstration that genes reside on chromosomes had an enormous impact on genetics.
Another landmark was the discovery of homeotic genes, which have a profound influence on development.
Fly work also played a major role in the discovery of clock genes.
Being rearable in large numbers, being an insect, and allowing mutants to be generated easily are advantages no other organism offered, which is exactly why the fly was such an outstanding material for genetics research.
Today, applications of the GAL4/UAS system, balancer chromosomes, and a wide array of other tools have all been developed and refined.
A few extra notes
Labs that study Drosophila rear the flies in cylindrical containers called vials, about 3 cm in diameter and 10 cm tall.
Most labs also have a dedicated rearing room where large numbers of these vials are kept.
You might imagine flies to be dirty, but their food is a jelly-like medium containing yeast, not raw meat, so bacteria don’t proliferate.
Flies are fairly hardy and relatively easy to keep.
That is surely part of why they have been studied for so long.
Dissections are done by hand with forceps under a stereomicroscope.
You are dissecting a fly roughly 2.5 mm long with forceps.
Behavioral experiments are possible too, and researchers have devised all sorts of ingenious apparatus for them.
Another wonderful thing about flies is that stock centers exist in several places around the world. They maintain large numbers of fly lines carrying specific genetic manipulations made in labs everywhere, and you can order whatever line you need from them.
That means you don’t have to build the line yourself and can start experiments right away.
(Doing the genetic manipulation yourself would take at least three months.)
Truly standing on the shoulders of giants.
Biologists often say that once you start working on Drosophila, you can’t go back to any other organism, which says a great deal about how well suited the fly is to research.