Why fruit fly brains might one day help humans ward off Alzheimer’s and Parkinson’s disease

Nicky Pellegrino

Health writer·New Zealand Listener·

3 Feb, 2026 05:15 PM4 mins to read

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The common fruit fly’s brain is surprisingly similar to human ones. Photo / Getty Images. Illustration / Listener

As unlikely as it may seem, fruit flies are becoming a powerful tool for helping us understand the complexities of the human brain. The common fruit fly has a surprisingly similar brain – although it is only the size of a poppy seed – and the processes involved in the
way it functions are similar too.

A major scientific breakthrough came in 2024 when an international team managed to fully map the neural connections of the fruit fly brain. They produced a wiring diagram, known as a connectome, finding over 50 million connections between almost 140,000 neurons and paving the way to produce similar maps for larger species, eventually including humans.

At Massey University’s Palmerston North campus, researchers are using fruit flies to investigate a process in the brain that may contribute to neurological disorders such as Alzheimer’s disease and Parkinson’s.

“Fruit flies are actually a very good model for studying humans,” says molecular biologist Helen Fitzsimons. “We can train them to learn something and test their memory. If we’re interested in a particular set of genes or proteins we can turn those genes on and off or move the proteins and test how that affects their memory.”

The Massey scientists test a fruit fly’s memory using a method known as courtship suppression assay, which harnesses the tiny insect’s natural instincts. A male fly is paired with a female that is non-receptive because it has recently mated and so rejects the male’s courtship. If the male fruit fly has learnt from and remembered this experience, the next time it encounters a non-receptive female it won’t put as much effort into trying to mate with it.

Research involving this technique has identified how disruptions in a protein known as HDAC4 (histone deacetylase 4) can lead to the formation of harmful clusters – or condensates – that interfere with healthy brain cell growth.

“HDAC4 is one of a group of proteins that is important for turning genes on and off,” says Fitzsimons, who has worked in this field for more than a decade. “Long-term memory involves turning certain genes on to help grow new synapses and make connections between the neurons stronger. We decided to focus on this family of proteins, turning them down or turning them off, and seeing what happened. HDAC4 was among the first we trialled and we found that when you turn it off the flies have impaired memory.”

Although HDAC4 is essential for brain health, excess amounts in the nucleus – the control centre of the cell – have been strongly linked to neuro-developmental disorders. Some studies of the post-mortem brains of people with Alzheimer’s have found that the more severe the disease, the more HDAC4 is on the scene. It has also been implicated in Parkinson’s disease.

“We don’t know specifically what it’s doing or know for sure that it’s contributing to the symptoms, but the evidence we’ve generated suggests it is because the more there is the worse the symptoms are,” says Fitzsimons.

One theory is that by sequestering other proteins into the clusters HDAC4 may stop them from doing their normal job.

“The other interesting thing,” says researcher Hannah Hawley, “is that while in a lot of diseases clusters are static, these are really dynamic. They move around inside the cell and there are ways we can dissolve them.”

Working with advanced microscopic techniques researchers can see the structures of a fruit fly brain and how the proteins are moving. They are even able to dissect the brains using very fine forceps.

“It’s a bit like peeling a mandarin with barbecue tongs,” says Fitzsimons. “It takes quite a bit of practice to get good at it.”

If these toxic proteins do prove to be a factor in neurological disease, then in the future drugs might be developed or repurposed to restore the correct balance of HDAC4 inside the cell, or prevent it from binding and forming clusters.

The next step, though, is to move on from fruit flies.“We hope to collaborate with other researchers,” says Fitzsimons, “and see if we can see the same thing happening in a rat, then test out whether we can disrupt these clusters and if that prevents memory loss or Alzheimer’s disease symptoms.”

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