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Switched-at birth twins offer clues to how genes get expressed

Institute News
Tuesday, December 20, 2016 - 4:45pm
A chance encounter between two sets of identical twins switched at birth has given scientists a rare opportunity to study how both pre- and postnatal environments and lifestyle can change how our genes are expressed in adulthood.

In the study, published in Epigenomics, scientists in Australia and the United States studied genetic expression in two sets of switched-at-birth identical male twins from Colombia, known as the ‘mixed-up brothers of Bogota’.

One unrelated pair grew up in the city, while the other unrelated pair lived in the country. Both unrelated pairs assumed they were fraternal (non-identical) twins, until a co-worker confused one of the twins for the other, and the hospital mix-up that occurred 25 years earlier was revealed.

That’s when the scientists arrived on the scene.

‘Studies of twins provide an opportunity to look closely at specific aspects of appearance, behaviour and health, and investigate whether genes or environment (or a combination) play a part in determining them,’ Associate Professor Jeff Craig explains.

‘And by studying identical twins, scientists are able to rule out a genetic influence.’

In this study, scientists were able to compare the time when the twins were together in the womb to that when they lived in separate environments.

In the collaboration, the researchers examined almost all of the twins’ genes and assessed their DNA methylation, a process that identifies which genes are expressed and which genes are not.

Most, but not all, of the twins’ genes showed similar DNA methylation. However, one of the twins showed a very different epigenetic profile from his genetically identical brother, possibly explained by his exposure to different prenatal events and/or different influences in his place of rearing.

‘We believe this was due to differences in environmental factors in the city and the country, such as exposure to UV and pesticides,’ A/Prof Craig explains.

Scientists also found, however, that one of the twin’s genetic profile was starkly different to his identical twin brother, suggesting they may have been influenced by different environments in the womb.

‘This is much like nature,’ A/Prof Craig explains. ‘The study shows we can be influenced by the environments we encounter before birth, and as we age,’ he adds.

‘As we can control some of these environments ourselves, many researchers think we can optimise our future health by treating our genes to the best combination of diet, exercise, nature and spiritual fulfilment.’

The collaboration published in Epigenomics included Australian researchers Jeffrey M. Craig and Yuk Jing Loke from the Murdoch Children's Research Institute in Melbourne, and Professor Nancy L Segal from California State University, and Yesika Montoya from Columbia University.

Findings will appear in a forthcoming book, Accidental Brothers, (Nancy L Segal and Yesika Montoya) to be published by St. Martin’s Press in 2017.

Media Contacts: Katherine Loftus 0416 013 689 katherine.loftus@mcri.edu.au

Available for interview: A/Prof Jeff Craig, Murdoch Children's Research Institute