Deep inside the cells of a fruit fly lie the same genes that drive human eye development. This allows scientists to research how a fruit fly’s eye develops in order to gain insight into how the same process occurs in humans.
Many genes that are important for human life were first discovered in the Drosophila melanogaster fruit fly. Genetic organisms — animals used to learn how cells and whole biological systems work — have been a huge boon for the scientific community, according to Dr. Deborah Garrity, associate professor in the department of biology.
Genetic organisms have allowed scientists to apply research done in a petri dish to a living system. Garrity said there is a lot that can be learned about human physiology from studying more simple organisms.
“Sometimes you’ll see these unexpected parallels even if the actual process is not absolutely identical among the organisms,” Garrity said.
Garrity explained that a select few model genetic organisms are chosen by the scientific community for practical reasons. The fact that there are only a few organisms used for this purpose means that a lot of data is available about the organism — from how to raise them to their genetic sequences.
Garrity does research on heart development and uses zebrafish as a model. She said that scientists will choose an organism because they are interested in a question and a certain organism will offer unique advantages to find an answer. Garrity uses the zebrafish because they develop as a transparent embryo, so she can watch how the heart forms under a microscope.
“That turns out to be a very convenient feature for the question that we want to study,” Garrity said.
Many of the human gene functions that we know of come from studies done on Drosophila fruit flies. Because of genetic conservation, flies and mammals such as humans share very similar genes with very similar functions.
“The main gene we study now is 90 percent identical between a fly and a mouse, and the function of the protein is the same when you look from a jellyfish all the way through the human form,” said Dr. Susan Tsunoda, associate professor in the department of biomedical sciences.
Tsunoda says that fruit flies are good model organisms for research because they have many of the same genes that humans do, but in a simpler system. This allows researchers to more easily see the effects of that particular gene on the system.
Human genes can also be expressed in fruit flies. Tsunoda’s lab is currently expressing the human form of amyloid beta, a protein thought to cause Alzheimer’s disease, in fruit flies. She describes that when this gene is overexpressed, flies have neurodegeneration, age-dependant learning impairment, early death and other analogs to Alzheimer’s disease.
“The system is distilled down a little bit, but it maintains complexity,” Tsunoda said. “The reason we use it is because it’s been such a good model for what happens in higher organisms.”
Dr. Leslie Stone-Roy, assistant professor in the department of biomedical sciences, uses mice in order to study taste. Right now she is trying to determine if taste cells are different in obese mice versus normal mice, something she hopes will be applicable to humans.
The taste bud is a small organ, with a lot of complexity. Stone-Roy points out that taste cells can’t be studied in a petri dish because they will de-differentiate into other cells without constant input from the system around it.
“You need the organ intact in a live animal otherwise you can’t study how they transduce taste stimuli, because the cell changes,” Stone-Roy said.
Stone-Roy said that by reducing or increasing the amount of protein being expressed using genetically modified mice, you can monitor their responses to certain tastes based on what taste receptor type you are changing. This allows Stone-Roy to determine which genes are important to tasting different molecules.
Stone-Roy says that if a scientist wants to study the effects and chemical interactions of a single protein, usually looking at it in a petri dish is enough. But if you want to understand how a cell interacts with it’s normal environment, you have to look at the whole picture.
“If you have a question about a system, you usually need a model organism,” Stone-Roy said.
Scientists study model organisms with the hope that they will gain knowledge to help them improve human health, animal health or the stability of the planet, according to Garrity. As such, scientists appreciate their responsibility over genetic organisms.
“What we’re trying to do here is very serious. We’re trying to come up with very credible experiments that use the best model organism to ask the most important scientific questions,” Garrity said.