Down

Genetic advance in Down’s syndrom.

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US scientists say they have moved a step closer to being able to treat disorders caused by an extra chromosome.

They have “switched off” the chromosome that causes the symptoms of Down’s syndrome in human cells in the lab.

The research, published in Nature, could one day lead to new medical treatments for the condition.

Future work may be of real benefit to people with Down’s syndrome, said the UK Down’s Syndrome Association.

Humans are born with 23 pairs of chromosomes, including two sex chromosomes, making a total of 46 in each cell.

People with Down’s syndrome have three – rather than two – copies of chromosome 21.

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This is an exciting breakthrough, but this process is still at a very early [cellular] stage and we are nowhere near seeing this procedure being used in the treatment of Down’s syndrome in people”

Dr Lucy RaymondUniversity of Cambridge

This causes symptoms such as learning disabilities and early-onset Alzheimer’s disease, as well as a greater risk of blood disorders and heart defects.

Gene therapy, which uses genes to treat illnesses, has been attempted for problems caused by a single defective gene. But until now, the idea of being able to silence the effects of a whole chromosome had appeared beyond the realms of possibility, even in the lab.

Now scientists at the University of Massachusetts Medical School have shown that, in theory, this might be possible but would take decades of research.

A team led by Dr Jeanne Lawrence inserted a gene called XIST into the stem cells of a person with Down’s syndrome grown in the lab.

‘Exciting research’

The gene plays a role in normal cell development by switching off one of the two X chromosomes present in female embryos, ensuring daughters avoid a double dose of X chromosome genes.

The experiments showed that the gene was able to silence the extra copy of chromosome 21, helping correct unusual patterns of growth in the cells.

Dr Lawrence told BBC News: “The research means that we have a new way – right away – to study the cellular basis for Down’s syndrome, that could help identify drugs for Down’s syndrome.

“At the same time we have made it conceivable – not necessarily possible or effective, that still needs to be proven – but conceivable that you could use just a single gene to correct the over-expression of the whole chromosome. So it makes genetic therapy for Down’s syndrome more conceivable where it really wasn’t before.”

Commenting on the study, Carol Boys, chief executive of the Down’s Syndrome Association, said it was exciting new research from a very well-respected team.

“The findings could have serious implications for future work that may be of real benefit to people with Down’s syndrome,” she said.

“We are a very long way from understanding how these findings might translate into clinical applications but it could be that they will be of great assistance in the search for conventional treatments for some of the health conditions that affect people with Down’s syndrome.”

Dr Lucy Raymond, from the department of medical genetics at the University of Cambridge, said the group had demonstrated an important proof of concept.

“This is an exciting breakthrough, but this process is still at a very early [cellular] stage and we are nowhere near seeing this procedure being used in the treatment of Down’s syndrome in people.”

Source: BBC

Brain cells give insight into Down’s syndrome.

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Brain cells have been grown from skin cells of adults with Down’s syndrome in research that could shed new light on the condition.

US scientists found a reduction in connections among the brain cells and possible faults in genes that protect the body from ageing.

The research in the Proceedings of the National Academy of Sciences gives an insight into early brain development.

Down’s syndrome results from an extra copy of one chromosome.

This generally causes some level of learning disability and a range of distinctive physical features.

A team led by Anita Bhattacharyya, a neuroscientist at the Waisman Center at the University of Wisconsin-Madison, grew brain cells from skin cells of two individuals with Down’s syndrome.

This involved reprogramming skin cells to transform them into a type of stem cell that could be turned into any cell in the body.

Brain cells were then grown in the lab, providing a way to look at early brain development in Down’s syndrome.

One significant finding was a reduction in connections among the neurons, said Dr Bhattacharyya.

“They communicate less, are quieter. This is new, but it fits with what little we know about the Down syndrome brain.”

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It seems to be another step forward, giving us insight into the effects of having three copies of chromosome 21”

Carol BoysChief executive, Down’s Syndrome Association

Brain cells communicate through connections known as synapses. The brain cells in Down’s syndrome individuals had only about 60% of the usual number of synapses and synaptic activity.

“This is enough to make a difference,” added Dr Bhattacharyya. “Even if they recovered these synapses later on, you have missed this critical window of time during early development.”

The researchers looked at genes that were affected in the stem cells and neurons from two individuals with Down’s syndrome.

They found that genes on the extra chromosome, chromosome 21, were increased greatly, particularly genes that responded to damage from free radicals, which may play a role in ageing.

This could explain why people with Down’s syndrome appear to age quickly, although this remains to be tested, said the University of Wisconsin-Madison team.

Commenting on the study, Carol Boys, chief executive of the UK Down’s Syndrome Association, said it was interesting work from an established, well-known team.

“It seems to be another step forward, giving us insight into the effects of having three copies of chromosome 21,” she said.

“We are learning more all the time about the mechanisms that cause certain aspects of the condition Down’s syndrome and this may ultimately result in the development of therapies for treatment.”

Source: BBC