Twins have long held a fascination in our popular imagination.
And while stories about telepathy are intriguing, says Director of Twins Research Australia John Hopper, twins hold the key to a more important mystery: nature versus nurture.
“Twins allow us to control perfectly for one of the main variables in our health – genetics. Then we can drill down on the role that environmental factors are playing,” says Professor Hopper, who has been leading the University of Melbourne based research facility since 1990.
“For example, studying twin pairs where one smoked and the other didn’t revealed tobacco use is a major cause of osteoporosis.”
Launched in 1982, the facility has more than 35,000 pairs of twins on its database and is the largest volunteer twin registry in the world.
And while the field has evolved considerably since, the facility remains an increasingly important tool for understanding how genetics and the environment interact to impact our health.
“We have seen a massive leap forward in DNA technology since the early 80s, notably the human genome project and the new field of epigenetics,” says Professor Hopper.
“Twin studies are very important for the translation of this new genomic knowledge into public health.”
To mark their 35th anniversary, we asked Professor Hopper and his team to nominate five of the most significant discoveries to come from its more than 230 twin studies.
1. Identifying the genetic and epigenetic risk of breast cancer
“Through studying twin pairs we identified the first gene that influences both mammographic density (the amount of white areas on a mammogram) and risk of breast cancer, called LSP1,” says Professor Hopper.
His team found monozygotic (identical) twins were highly similar for mammographic density, which predicts future risk of breast cancer. Dizygotic (non-identical) twins were half as similar, suggesting a major genetic role underlying this risk factor.
“Incredibly, we also found a new epigenetic risk factor for breast cancer that is determined in the uterus – a finding we could only have discovered by studying twin pairs,” says Professor Hopper. The next step, he says, is to find out why the environment in the womb influences the risk of breast cancer.
Ultimately, this work could change breast screening and breast cancer prevention across the world. Professor Hopper and his colleagues are working with Breast Screen Victoria to develop plans for tailored screening, where the timing of screening is based on personal risk, rather than age alone.
2. Epilepsy can be inherited
Twenty years ago the medical profession thought epilepsy was an acquired disease, caused by head injuries or a difficult birth.