Topic summary: Suppressing the extra chromosome in Down’s syndrome

nuffield_topic-summary-694x317Suppressing the extra chromosome in Down’s syndrome

Published November 2016

Research on the silencing of the extra copy of chromosome 21 has led to speculations that a chromosomal therapy for Down’s syndrome could be developed in the future.

Are there recent scientific, legal or social developments?

In July 2013, a team of scientists from the University of Massachusetts Medical School published research detailing a method of silencing the third copy of chromosome 21. Using genome editing techniques the team were able to insert a XIST transgene into chromosome 21 which induced chromosome-wide transcriptional silencing of one copy of chromosome 21 in an in-vitro model. This was announced as a first major step towards ‘chromosome therapy’ for Down’s syndrome. The therapy may not block all gene expression in the extra chromosome however. Scientists have also identified signalling pathways as possible therapeutic targets in mice models of Down syndrome and shown improvements in cognitive function.

Are there complex ethical issues?

Poor health is not inevitable in people with Down’s syndrome and most children will now go to a mainstream school. Studies have shown that people with Down’s syndrome are happy with their lives and like who they are. Life expectancy for those with Down’s syndrome has also increased substantially and is now around 60 years in the developed world. However, individuals with Down’s syndrome are at increased risk of developing a number of health conditions (such as congenital heart disease, duodenal atresia and early-onset Alzheimer’s disease) and will all have some degree of learning disability.

Some argue that a chromosomal therapy could benefit individuals with Down’s syndrome, and that if such treatments are available, then people have a right to access them. Particularly in areas of the world where people with Down’s syndrome are more likely to experience discrimination, or where socio-economic resources are less, it may be very important to enable individuals to lead more independent lives. Yet there has also been criticism of the focus on ‘curing’ Down’s syndrome, rather than aiming to facilitate and support individuals with the condition in their daily lives. Some view disability as an important aspect of an individual’s identity, and are concerned that the idea of a cure further perpetuates the notion that a life with Down’s syndrome is less valuable, leading to increased stigma and discrimination towards those living with the condition. Many people hold the view that Down’s syndrome is associated with particular facets of personality (such as being more open, caring and humorous) and that people with Down’s syndrome have much to contribute to society. Some go as far as to dispute whether Down’s syndrome is in fact a disease at all. This also raises wider questions about how society benefits from diversity and the opportunities for compassion and solidarity to which it may give rise.

Is there a potential policy impact?

There will need to be further regulation of genome editing techniques as they become increasingly available in the future, as well as widespread public consultation as to whether therapies to ‘cure’ Down’s syndrome or other chromosomal disorders are in the interests of society. Policy makers may also need to review whether limited funding resources should be directed towards such research or not.

Is it a subject of public concern?

About 775 babies are born with Down’s syndrome each year in the UK, and all pregnant women are routinely offered prenatal screening for Down’s syndrome. Currently up to 90% of women who are diagnosed with a baby with Down’s syndrome during pregnancy will choose to terminate. A recent BBC2 documentary entitled ‘A World without Down’s Syndrome?’ questioned the impact of non-invasive prenatal testing (NIPT) on the number of terminations and the effects of making NIPT available on the NHS. The documentary sought to challenge the view that Down’s syndrome is a catastrophe for families and that instead individuals with Down’s syndrome are simply ‘types’ of people with many admirable qualities. Indeed some people believe that we would be worse off in a world without Down’s syndrome and there are organisations that campaign on this issue. The documentary received widespread media attention and sparked public debate on the topic.

Is consideration timely?

The research into a chromosomal therapy for Down’s syndrome is still at a very early stage, and may not be available for many years, if at all. However, considering that such research is currently underway, it may be timely to discuss the future implications of this and other ‘cure-directed’ therapies for Down’s syndrome.

Can the Council offer a distinctive contribution?

Whilst many of the questions this research raises may be addressed within the current council projects on NIPT and genome editing, there may be scope for a spin-off project to look more closely at the notions of ‘disease’ or ‘disorder’ which have been attributed to Down’s syndrome and to bring together expert and public opinion on this. The Council might consider a larger project looking at the impact of new genetic technologies on conditions involving learning disability or behavioural disturbance (such as autism, ADHD). This would follow-on from previous work on mental disorders and genetics and genetics and human behaviour. Or it may be interesting to consider more broadly the topic of personality and how new biomedical advances might restrict the range of personality variations in the future.

Possible future work topics

This is one of the topics that have been suggested as possible project areas for further investigation by the Council. These topic summaries do not aim for comprehensiveness; rather, they are intended to sign-post some of the key considerations and to provide a starting point for discussion. Each summary includes links to relevant publications on the topic.

Possible future work topics are selected and/or revised regularly, following discussions among members of the Future Work Sub-Group and the Council. This set of topic summaries was published in November 2016.

Previous work

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