Monstrous Mutations in Our Creepy, Crawly Friend: The Fruit Fly

Artificially colored images of fruit flies taken with a scanning electron microscope. (Left) Fruit fly with eyeless mutation and lacking compound eyes. (Right) Normal fruit fly with compound eyes colored in red. (Credit: Jürgen Berger and Ralf Dahm, Max Planck Institute for Developmental Biology, Tübingen, Germany.)  

Artificially colored images of fruit flies taken with a scanning electron microscope. (Left) Fruit fly with eyeless mutation and lacking compound eyes. (Right) Normal fruit fly with compound eyes colored in red. (Credit: Jürgen Berger and Ralf Dahm, Max Planck Institute for Developmental Biology, Tübingen, Germany.)
 

The unforgettable final scene of The Fly features a poor little fly stuck in a spider's web, screaming “Help me! Help me!” before being crushed to death. Although scientists in the real world don’t have disintegrator-integrator devices that could accidentally swap body parts between humans and flies, there are many remarkable genetic mutations that scientists can study to better understand how our bodies develop and why we have certain diseases. Many of these were first discovered in the fruit fly. Here are a few of these monstrous mutations for your viewing pleasure - hope they don’t give you nightmares!


eyeless is a gene important for making flies’ large compound eyes. If this gene isn’t expressed at the right time and in the right place, flies are born without eyes. If eyeless is expressed in the wrong body region during development, such as the legs or antennae, those parts of the body end up with eyes on them.

 

Artificially colored images of fruit flies taken with a scanning electron microscope. (Left) Expression of the gene Antennapedia in antennae as they develop causes them to transform into legs. (Right) Normal fruit fly with properly formed antennae. (Credit: Jürgen Berger, Max Planck Institute for Developmental Biology, Tübingen, Germany.Visuals Unlimited.)

Artificially colored images of fruit flies taken with a scanning electron microscope. (Left) Expression of the gene Antennapedia in antennae as they develop causes them to transform into legs. (Right) Normal fruit fly with properly formed antennae. (Credit: Jürgen Berger, Max Planck Institute for Developmental Biology, Tübingen, Germany.Visuals Unlimited.)

The gene Antennapedia is responsible for instructing cells to form legs in the fruit fly. During development, cells have a choice to become antennae or legs. Antennapedia is crucial in making this decision. If Antennapedia is expressed in cells fated to become antennae, they transform into legs. Conversely, if leg cells don’t express Antennapedia, they develop into antennae instead.

(Top) Fruit fly embryo, white bands define the borders of body segments. (Middle) Embryo of fruit fly with mutated form of hedgehog. The embryo is missing segments and has spike-like structures along its outer surface. (Bottom) European hedgehog. (Modified from Han et al., 2004, CC by 4.0 and European hedgehog (Erinaceus_europaeus), CC BY-SA 2.5)

(Top) Fruit fly embryo, white bands define the borders of body segments. (Middle) Embryo of fruit fly with mutated form of hedgehog. The embryo is missing segments and has spike-like structures along its outer surface. (Bottom) European hedgehog. (Modified from Han et al., 2004, CC by 4.0 and European hedgehog (Erinaceus_europaeus), CC BY-SA 2.5)

The fruit fly gene hedgehog and one of its counterparts in vertebrates (sonic hedgehog, named after the infamous SEGA character) helps to construct our body plan as we develop. Without it, pieces of the body are literally missing. In flies, the egg actually resembles a hedgehog, spikes and all. While humans lacking sonic hedgehog don’t develop spikes, they can have some serious developmental defects like Cyclopia
 

Jennifer Lovick (@drjkyl)
Senior Editor, Science in Entertainment, Signal to Noise Magazine
PhD, Molecular, Cell, and Developmental Biology