How can fruit flies help us understand autism?

Contrary to what is often portrayed on television, scientists cannot investigate human disease the same way Dr. Frankenstein studied the creation of life. Instead of human experimentation, researchers have figured out how to use model organisms.

What is a model organism?

A model organism is a species that is studied intricately by scientists to further understand biological processes common to most life forms. A discovery made in the model organism can provide insight into the inner workings of humans. This means that in addition to improving our understanding of biological processes in general, research with model organisms also helps us develop treatments for human disorders and diseases.

One versatile model organism is the common fruit fly: Drosophila melanogaster.

Fruit flies are easy to maintain in a laboratory setting and their short life cycle allows multiple generations to be studied within a short period of time. In addition to these advantages, the paramount aspect of this tiny organism lies in the simplicity of its body composition; four pairs of chromosomes provide easy access for genetic modification. For these reasons, Drosophila melanogaster is one of the most common model organism used for genetics and developmental biology research.

Within the context of researching human diseases, it is estimated that humans share 75% of disease-related genes with fruit flies.

What does this mean?

This means that certain genes implicated in human diseases have similar DNA sequences and biological functions—at the molecular level—in both humans and Drosophila.

For example, our research lab, led by Dr. Kimberly Mulligan, is studying the developmental interaction between environmental chemicals and a gene called fragile X mental retardation1 (fmr1), which causes fragile X syndrome (FXS) and is associated with autism spectrum disorder (ASD) in humans.

Fmr1 is a gene that is essential for normal brain development in both humans and fruit flies. Mutations in FMR1 are the most common single gene cause of ASD in humans; approximately 40% of individuals with FMR1 mutations are diagnosed with ASD.

Since the Fmr1 gene in fruit flies carries out the same molecular functions as humans, we can conduct experiments using Drosophila to learn about how this gene functions to help brain cells develop—which will help us understand how this gene works in human brain cells. (Which, obviously, is a better approach than performing disturbing human experimentation like Dr. Frankenstein.)

As an example, we can dissect developing fruit fly brains and use a laser-scanning confocal microscope to visualize brain cells under high magnification. This allows us to see how Fmr1 mutations can change the shape of brain cells or impair their ability to form important connections with other brain cells. This type of research provides clues as to why mutations in this gene disrupt human brain development, which can help inform development of potential treatments for ASD and FXS.

Although there are big differences between fruit flies and humans, the use of Drosophila as a model organism has provided important insights into how genes function at the molecular level for decades. We hope our work with fruit flies will do the same for ASD and FXS.