Raising the baa

by Nicky Pellegrino / 22 October, 2015
Thanks to New Zealand sheep, researchers are closer to finding treatment for a distressing genetic disorder.
Sheep With Glasses
Photo/Getty Images

If a cure is found for the devastating neuro­logical disorder Huntington’s disease, the sheep at Rotorua’s Agrodome will have played a part. It was watching the farm show and speaking with the animal trainers there that inspired Professor Jenny Morton to develop research she is optimistic will help lead to a breakthrough for Huntington’s, and potentially benefit the investigation of other diseases.

Kaikohe-born Morton is a neuroscientist based at the UK’s Cambridge University. She became interested in Huntington’s after a lunch where she sat next to a woman who was nursing her husband through the disease and facing the prospect that her children had inherited it.

Huntington’s disease is a relatively rare condition caused by a single gene mutation. It causes pro­gressive degeneration in nerve cells in the brain and results in problems ranging from movement and muscular issues, to sleep disorders, depression and cognitive decline. These worsen over time, eventually resulting in death.

Morton is working on finding an early intervention to reverse or even prevent this decline before symptoms appear. That’s where the sheep come in. Using them, she has created methods of monitoring the disease and testing potential therapies, inadvertently becoming an animal-behavioural expert along the way. “People said you’ll never teach a sheep to do anything, and I thought they were probably right,” she says. “I assumed sheep were stupid, but they are absolutely not.”

When Morton started her research, there was little information to be had, so she took a three-month sabbatical and spent time talking to farmers and scientists. It wasn’t until her visit to the Agrodome, however, that she began to feel hopeful that sheep could be trained to do cognitive tests relevant to human diseases.

“Sheep are fascinating,” she says. “They’ve got big brains – I’d challenge someone who wasn’t an expert to tell the difference between a monkey brain and a sheep brain. And they are immensely trainable. You can take any old sheep out of a field and in two weeks teach it to do a task it might take a monkey nine months to learn. All of our sheep will walk on a lead but don’t really need one because, once they know you, they’ll come when they’re called.”

Sheep have other advantages. They have a reasonably long life expectancy – Morton has some that are 18 – which makes them more useful for investigating slow-­developing or late-onset diseases than, say, mice, which live only a couple of years.  “And sheep are easily managed,” she says. “They live in a paddock with other sheep, so there are no abnormal environment constraints.”

She did have concerns that flock mentality would create issues, but has found that once the sheep become familiar with their handlers, they are happy to work alone for a couple of hours at a time.

The test she has devised involves sheep walking through a maze and making a choice by touching a computer screen with their noses. When they choose the screen with the correct symbol, they get a food reward. The symbols are then switched and the sheep have to learn that the rules have changed. Morton says this is something Huntington’s patients have real problems doing.

She has also monitored flocks of sheep using wristwatch-type devices to trace the breakdown of circadian rhythms that Huntington’s sufferers commonly experience. The Huntington’s flock failed to settle after sundown, remaining wakeful for two or three hours longer.

“They were only 18 months old, but had this clear circadian disturbance as if they weren’t generating the right cues for their bodies to settle down.”

Morton’s sheep are genetically engineered to develop Huntington’s, but there are many other conditions that naturally occur in them, including Batten disease. Lincoln University researchers have been working with a Batten flock for more than 30 years.

“There are probably 17 rare genetic disorders that naturally occur in sheep,” says Morton. “There may be more, but we just don’t look for them because if a sheep has a problem, we send it to the works.”

Morton believes sheep have the potential to further our knowledge of many other conditions, including Alzheimer’s (they naturally make the tangles in the brain cells that, along with amyloid plaques, are a known hallmark of the disease).

For Huntington’s, it is a long-term project. So, is Morton expecting to see her work lead to a cure?

“I hope so,” she says. “If you’d asked me five years ago, I’d have said I’m not sure, but now I’m actually quite optimistic about it.”

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