Scientists implant human chromosome in mice
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Scientists have transplanted a nearly entire human chromosome in mice in a medical and technical breakthrough that could reveal new insights into Down’s syndrome and other disorders.
The genetically engineered mice carry a copy of the human chromosome 21. It is the smallest of the 23 pairs of human chromosomes with about 225 genes.
Children suffering from Down’s syndrome, which is one of the most common genetic disorders, inherit three copies of the chromosome instead of two.
The achievement caps 13 years of research by scientists at the National Institute for Medical Health in London and the Institute of Neurology.
“We are very optimistic that we will be able to get insights into what goes wrong with people with Down’s,” said Dr. Victor Tybulewicz, who headed the research team.
Down’s syndrome, which affects about one in every 800 live births, impairs mental and physical development. People with the condition may also have heart defects, hearing problems and have a higher risk of leukaemia and early-onset Alzheimer’s disease.
“These disorders that people with Down’s are more prone to get are ones that also affect all humans. It is entirely possible that if we gain insights into what is going wrong in the Down’s syndrome people we will also gain insights into what goes wrong during those disorders amongst the rest of us,” he added.
MATCHING GENES TO DISORDERS
Dr. Elizabeth Fisher, of the Institute of Neurology, said the technology will help scientists tease out the genes that cause the different aspects of Down’s syndrome and susceptibility to other diseases. “We believe this new technology will help us work out why this is, and what to do about it,” she said.
In research reported in the journal Science, the researchers described how they removed the chromosome from human cells. Chromosomes are found in the nucleus of a cell and contain the genes.
The human chromosome was mixed with mouse embryonic stem cells and a chemical was added that caused them to fuse. The stem cells that absorbed chromosome 21 were then injected into mouse embryo, which was re-implanted into the mother. The resulting mouse had a copy of the human chromosome.
Although the mice look normal, they show various features associated with Down’s syndrome.
The Down’s Syndrome Association in Britain welcomed the research, saying it could have a positive impact on the lives of people with the condition.
“Any research that could lead to a greater understanding of why people with Down’s syndrome are more susceptible to certain medical conditions is obviously extremely important, although it must be recognised that this research does not herald a ‘cure’ or a ‘treatment’ for Down’s syndrome,” the association said in a statement.
But Human Genetics Alert, an independent watchdog that focuses on the ethics of human genetics, described the breakthrough as frightening because animals with human genes are being created.
“It is worrying that there has been no public debate about whether this kind of technique ought to be allowed. I think we need a lot more public debate about that,” Dr. David King told Reuters.
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