Chinese scientists have made clones of a gene-edited macaque to aid research of circadian rhythm disorders that are linked to sleep problems, depression and Alzheimer's disease.

Key points: Five macaques were cloned from an adult gene-edited donor prone to sleep disorders

Five macaques were cloned from an adult gene-edited donor prone to sleep disorders Chinese scientists say their work is ethical and will help treat humans in the future

Chinese scientists say their work is ethical and will help treat humans in the future China, the only country to clone primates, also cloned two macaques last year

It was the first time multiple clones had been made from a gene-edited monkey for biomedical research, the agency said.

The clones were born at the Institute of Neuroscience at the China Academy of Sciences in Shanghai.

A gene-edited monkey most prone to the disorder was selected as a donor, and its fibroblasts were used to make five cloned monkeys, state outlet Xinhua said, citing Chinese journal National Science Review.

State outlet China Daily said the clones would pave the way for more research into such problems in humans, which have become a major mental health concern.

The gene is BMAL1, which helps regulate the circadian rhythm but scientists made it inoperative using a gene-editing tool, known as CRISPR.

The cloned monkeys already show signs of "negative behaviour", including sleep disorders, as well as elevated levels of anxiety, hormonal disorders, depression and "schizophrenia-like behaviours", the paper added.

"Disorder of circadian rhythm could lead to many human diseases, including sleep disorders, diabetic mellitus, cancer, and neurodegenerative diseases, our BMAL1-knockout monkeys thus could be used to study the disease pathogenesis as well as therapeutic treatments," said Hung-Chun Chang, senior author and investigator at the Institute of Neuroscience.

'The genie's out of the bottle'

The young macaques are already showing signs of circadian rhythm disorders. ( China Daily via Reuters )

Xinhua said the program, supervised by the institute's ethics panel, was in line with international ethical standards for animal research, though many will disagree.

"Genetically manipulating and then cloning animals is a monstrous practice that causes animals to suffer," Dr Julia Baines, science policy adviser at PETA UK, told news.com.au.

This controversial breakthrough comes on the heels of another, when late last year a Chinese professor used CRISPR to edit the genes of twin babies.

He was excoriated by the international community, and a government investigation found he broke rules, evaded oversight and forged ethical review papers in his search for fame and fortune.

China is still the only country that has cloned a primate.

Last year, Chinese scientists cloned two macaques using the same technique that produced Dolly the Sheep, and that ultimately produced this litter.

"The genie's out of the bottle now," Jose Cibelli, a cloning expert at Michigan State University in the US, said at the time.

This is the most recent in a series of audacious gene-editing and cloning experiments by Chinese scientists. ( China Daily via Reuters )

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