Mouse with human genes helps Down's research

A mouse has been given Down's syndrome by scientists who have created a rodent that in genetic terms is one per cent human.

Researchers managed the feat by implanting almost an entire human chromosome for the first time.

The London-based team has been overwhelmed with requests from fellow scientists to obtain the modified mouse, which will make it easier to understand the effects of Down's syndrome, which is linked with types of leukaemia, heart disease and Alzheimer-like symptoms relatively early in life.

The research, published today in the journal 'Science', could eventually help to prevent these conditions in people with Down's and in the rest of the population. In the longer term, it could aid efforts to understand and ameliorate other effects of Down's.

But this, the first true mouse model for human Down's syndrome, could prove controversial: it is a small but dramatic example of a burgeoning trend to genetically alter animals. The trend is opposed by animal rights campaigners because it is driving a rise in the numbers of rodents used in experiments.

The team stresses that this mouse is far from being 'humanised' and says the aim is not to "treat" Down's syndrome but to understand the disorders that arise from the syndrome, which affect everyone.

The research, led by Dr Victor Tybulewicz, of the National Institute for Medical Research in Mill Hill, and Prof Elizabeth Fisher [Institute of Neurology] was funded by the Medical Research Council and the Wellcome Trust.

Prof Fisher said: "People with Down's syndrome have particular susceptibilities for some diseases such as leukaemias and auto immune disorders. We believe this technology will help us work out why this is, and what to do about it."

Down's syndrome is caused by the presence of three copies of chromosome 21 instead of the normal two. As yet, it is unclear what causes this extra chromosome to be present, although the risk rises with maternal age. ...

The researchers decided to mimic the disease in mice because man and mouse each has 25,000 genes and shares around 99 per cent of them. However, the genes are not arranged in the same way.

Roger Highfield, 'The Daily Telegraph'