MONKEYS genetically engineered to get the deadly neurological disease Huntington鈥檚 could provide a unique way to test potential treatments because of their cognitive and genetic similarities to humans.
鈥淢onkey models may have a privilege over other animal models,鈥� says Anthony Chan, a biologist at Yerkes National Primate Center in Atlanta, Georgia, whose team engineered five rhesus macaque monkeys to churn out the mutant protein that causes Huntington鈥檚.
Researchers routinely splice human genes in and out of mice to give them diabetes, cancer, and heart disease. But mice are of limited use when investigating brain diseases such as Huntington鈥檚: people who have it can鈥檛 control their movement, speech or swallowing, and their cognitive abilities deteriorate. Mice engineered to express the Huntington鈥檚 protein don鈥檛 jerk their muscles like humans do and it can be tough to gauge their cognitive decline.
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To see if primates might offer more insight into the disease, Chan鈥檚 team used a virus to insert the Huntington鈥檚 gene into the DNA of 130 macaque eggs, along with a gene that makes a fluorescent green jellyfish protein. The researchers then fertilised the eggs and implanted them into eight mothers.
All the monkeys born expressed the green protein, indicating that gene transfer had been successful (see picture), and some already appear to have had the monkey equivalent of Huntington鈥檚. The brains of one set of twins, who died a day after birth, were littered with clumps of the mutant protein found in humans with Huntington鈥檚, while a lone animal, who died a month after birth, jerked involuntarily (Nature, ).
Meanwhile, Chan鈥檚 team is watching two surviving twins for symptoms, which can strike swiftly and unpredictably in humans. They will also analyse the monkeys鈥� blood for early predictors of the disease.
鈥淚 think this is amazing,鈥� says Chris Ross, a neuroscientist at Johns Hopkins University in Baltimore. He studies mouse forms of Huntington鈥檚 but says monkeys could help test several potential drug treatments. Huntington鈥檚 affects 1 in 10,000 people of European descent.
Transgenic monkeys with other human diseases, such as early onset Alzheimer鈥檚 or fragile X syndrome, are likely to follow, says Gerald Schatten, a biologist at the University of Pittsburgh in Pennsylvania.
鈥淭ransgenic monkeys with other human diseases, such as early onset Alzheimer鈥檚 or fragile X syndrome, are sure to follow鈥�
Yet even researchers accustomed to animal research say working with transgenic monkeys should always be a last resort. 鈥淭here should be higher levels of scrutiny in working with our closest animal cousins,鈥� Schatten says.
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