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World's largest twin database will help us to understand the genetics of rare diseases

6 April 2009
Appeared in BioNews 502

Plans for a new database of 300,000 pairs of twins have been unveiled by researchers at Kings College London. The £20 million TwinBank project will be ten times larger than the biggest twin samples assembled previously and will allow scientists to investigate the genetic and environmental origins of disease and behaviour through comparisons of identical and non-identical twins on an unprecedented scale.

Identical twins are genetic clones of each other and occur when an embryo divides in two, whereas non-identical or fraternal twins share no more DNA than ordinary siblings as they occur when two separate eggs are ovulated and fertilised. Because both types of twins share the same womb and experience the same family background, comparisons made between them can yield important insights into heritability and the age old argument of nature versus nurture. If identical twins share a trait more commonly than fraternal sets, it is highly probable to have a genetic component.

Identical twins are more similar to one another than fraternal pairs in all manner of human traits such as IQ (intelligence quotient), political conservatism, religiosity, homosexuality and personality indicators such as extroversion and neuroticism. They are also more likely to be concordant for medical conditions such as heart disease, autism, diabetes, migraine and many cancers. However, research into the genetics of rare diseases such as schizophrenia, leukaemia and motor neuron disease, would require a registry of hundreds of thousands of twins in order to be confident of finding enough pairs who are affected. The size of TwinBank would enable twin studies to investigate these rare medical conditions, which affect one in 100 people or fewer.

A further opportunity will be to investigate epigenetics, a process by which the activity of genes is regulated by chemical markings. Identical twins have the same raw DNA code, but their epigenetic programming is different. TwinBank will help scientists to investigate this for clues to disease. Other applications could include examining the effects of social issues such as parenting, education and the effects of poverty.

There are an estimated 640,000 sets of twins in Britain and the study aims to contact 500,000 of these with the hope of recruiting 300,000 of them to the database. DNA and other health data on the twins would also be collected through the NHS and held confidentially, with participants free to withdraw from the scheme at any time.

The initiative was designed by Robert Plomin, Professor of Behavioural Genetics, and Tim Spector, Professor of Genetic Epidemiology, and the NHS has approved the idea and organised a pilot study. 'TwinBank would give us unprecedented opportunities to study the genetic and environmental factors that influence human health and behaviour,' Professor Plomin said, adding: 'It would be a dream resource.'

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