It’s in their genes: What makes fruit flies the ultimate model organism

It’s in their genes: What makes fruit flies the ultimate model organism

Written by: Jocelyn Drasdauskis, Diane Jeon

Contributed to by: Chris Fetterly, Anzer Khan

 

What is a model organism?

Mendel's pea plants, Darwin’s finches, and Thomas Morgan Hunt’s fruit fly—what do they all have in common? They were all model organisms for increasing scientific knowledge and new discoveries. Scientists have used a combination of reductionism and model organism biology to understand bigger and more complex processes for over 100 years. A model organism is defined as a non-human organism which is used in the laboratory to understand fundamental biological processes. They range from brewer’s yeast to frogs, mice to small worms, and zebrafish to fruit flies. Working from lower to higher “complexity” of organisms allows a greater understanding to be achieved like building blocks in a tower. Over time the learning from one system is directly applicable to more complex ones and builds our overall knowledge. For example, scientists can build upon information learned from the DNA of bacteria and apply it to the more complex gene structures and inheritance patterns in zebrafish to figure out what genes need to be activated at different stages of development.

model organism building blocks

The choice of model organism to use varies greatly depending on the processes scientists hope to understand. With organ systems that have been mapped for hundreds of years, model organisms provide valuable insights into human genetics, development, diseases, and new drug discoveries. As research dollars are often limited, scientists use model organisms that can not only answer the research question at hand, but are also convenient and cost-effective to maintain in a laboratory setting.

Our favourite model organism, Drosophila melanogaster (D. mel), or the common fruit fly, is one of the most well-understood of all model organisms and continues to stand at the forefront of biological research. Let’s dive in to why D. mel has stood the test of time in research labs around the globe.

What is Drosophila melanogaster?

The fruit fly that spirals around our kitchen is no ordinary specimen and is more important than you may think. In fact, more of those little flies have been to space than humans have. Drosophila melanogaster is a species of fly that can be distinguished from others by its red eyes, tan thorax, and black abdomen. No larger than a few millimetres, these flies have been studied by scientists for over a century to bring about our understanding of human genetics, development, and health. Due to its rich scientific legacy, contributing to 6 Nobel prizes, D. mel is often described as the model organism for biological and genetic research.

Why are fruit flies an ideal model organism for research?

What model do you need if you are trying to piece together the building blocks of life and human disease? You would need a model that:

  • has a simple genetic makeup which can be easily manipulated,
  • analogous genes and physiological structures to humans,
  • reproduces quickly so you can do many experiments over time, and
  • one that is inexpensive to rear in a lab setting.

By checking all of these boxes, Drosophila melanogaster has retained its position as a superior model organism throughout history.

The D. mel genome is relatively simple and has only four chromosome pairs compared to the 23 of humans. Flies also have ‘polytene’ chromosomes, meaning they are physically large with thousands of DNA strands that can be easily viewed under a normal microscope. These large chromosome structures allowed the first geneticists to visibly see when DNA rearrangements occurred and enabled genetic research to progress before technology had advanced enough to see the DNA in other organisms. Flies are also easy to genetically manipulate; they have observable physical traits (phenotypes) that allow scientists to quickly discern between different fly populations during experiments.

drosophila melanogaster future fields

Fruit flies have many analogous genes and physiological structures to humans, such as a gut, brain, eyes, and even hair structures. This ranks D. mel higher than unicellular model organisms like bacteria or certain fungi, offering more in-depth insight into human organs. These similarities translate to shared genetics as well, with humans having a 60% identical genetic makeup to D. mel. In fact, almost 75% of disease-causing genes in humans have a recognizable analogue in flies, making flies an effective model to study many different disease processes. Through these similarities, scientists are able to link what occurs to D. mel in different experimental conditions directly to what happens in humans. One example is when male flies are rejected by potential mates they have been shown to consume more alcohol. How relatable!

Fruit flies are perfect for tight academic budgets as they can be bred easily and scaled affordably. Having a short reproduction cycle, flies can produce adults from an egg in 11-14 days which makes the study of several generations and inheritance patterns possible in just a few months. On top of their genetic advantages and fast reproduction cycle, the nutritional requirements (simple carbs and proteins), reduced water consumption, and lower temperature at which they thrive (22-25 °C), make fruit flies a sustainable and cost-effective study organism.

Flying across industries: Experimental Designs and Drosophila

From COVID-19 vaccine research, to understanding neurodegeneration and cancer biology, to cellular agriculture, the flexible model fruit fly has not only helped us to understand many human processes but provide the basis for future bioproducts. When the pandemic hit and researchers needed models to understand the immune response to COVID-19 infection, they once again turned to Drosophila melanogaster. Due to in-depth understanding of the fly genome, scientists were able to look at the most pathogenic genes related to COVID infection and propose potential therapeutics. Similarly, D. mel is an excellent model organism for studying ageing and neurodegeneration. Models for Parkinson's and Alzheimer's diseases have been created in flies to mimic the brain in patients where experimentation would be unethical. Using fruit flies, scientists gained an understanding of how the diseases progress over time and created novel therapeutics.

Fruit flies have also been used to understand the etiology of complicated diseases such as cancer. One of the greatest contributions of the fly to the study of cancer biology was the elucidation of the Ras signalling pathway more than 20 years ago. By understanding how Ras signalling can affect the proliferation and differentiation of cancer cells, scientists were able to generate several theories on how the disease originates and evades the immune system. This knowledge is still being used to come up with new therapeutics and understand why some cancers return after initial remission.

Flying forward: Bioproducts with a positive impact on the planet

Now that we are in the era of where biotech means cleantech, Future Fields poses the question: what if we harnessed the advantages of Drosophila melanogaster as a model organism not only for biology, but for fighting climate change?

Academic, industrial, and pharmaceutical research labs are at the forefront of bio-innovation, but their building blocks face some wasteful challenges. According to a 2019 analysis, nearly 300 million litres of cell culture waste is generated annually across industries. If there is a way to improve the environmental impact of downstream processing, bio-industries could raise the bar for sustainability in sciences.

One way to tackle this is to minimise the environmental impact at the cell level. To grow their cellular innovations, scientists rely on traditional growth factors often produced by simple organisms like bacteria and yeast cells. These are housed in bioreactors, which come with a large environmental and economic price tag. Like the reductionist beginning of model organisms, these simple systems have been pushed to their limits by decades of research and are still unable to meet the world’s growing need and reliance on biological industries.

drosophila melanogaster future fields entoengine

Like the scientists looking to understand complex biology before us, Future Fields turns to the common fruit fly in search of a new solution expanding on what we have learned from traditional growth factor production models. Our EntoEngine™ takes advantage of a century’s worth of genetic knowledge, a short reproduction cycle, and the sustainable rearing methods of Drosophila melanogaster to create what we see as the future of recombinant protein production.

Future Fields is proudly fly by design. Harnessing the genetic prowess of the fruit fly, Future Fields provides scientists with the quality biomolecules they need to economically and sustainably do great science.



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