7’6″ basketball player helps us understand the genetics of extreme height
Many of us have wondered about the genetic basis of height and compared how tall we are with our parents and siblings. However, understanding how our DNA affects height could also reveal a lot about other characteristics influenced by our genes, such as our risk of disease.
A featured study entitled “Common DNA Variants Accurately Rank an Individual of Extreme Height,” published in Hindawi’s open-access International Journal of Genomics, analysed the genetics of Shawn Bradley, a 7’6” former professional basketball player. The research team found that Shawn has a rare combination of common genetic characteristics that are associated with height. Using this information, the team correctly predicted that Shawn was the tallest person in a sample of 1,020 individuals, suggesting that the technique could be used to identify other complex traits, such as diseases.
Height as a model for genetic insight
Height is a complex biological characteristic affected by a variety of genes and external factors, such as nutrition. Researchers have been examining the genetic factors involved in height as it can be measured easily and non-invasively and is therefore useful in providing insights into how our genes affect us.
“Having a study subject with extreme height and no other medical conditions was vital to being able to explore these questions,” explains Professor John Kauwe of Brigham Young University in Utah. “Shawn Bradley, at 7’6″, was a perfect subject for our work.”
How do polygenic scores measure up?
Polygenic scores are a measure of multiple genetic features, such as small mutations, that are known to contribute to a specific characteristic, such as height. Typically, polygenic scores aren’t accurate in predicting complex characteristics in one individual as the interplay between genes and other factors is very complex and researchers don’t yet fully understand all the processes involved. However, Kauwe and his colleagues had a hunch that for someone with extreme height, the polygenic score might be more informative.
Consequently, they analysed genetic features associated with height for Shawn and a sample of 1,020 volunteers, then calculated the resulting polygenic scores for height. They found that Shawn had an extremely rare combination of many common genetic characteristics associated with height. This meant that the polygenic score generated for Shawn correctly ranked him as the tallest person in the sample of participants.
Interestingly, although the polygenic score correctly identified Shawn as the tallest member of the group, it only predicted him to be 10.32mm taller than average, so clearly other external factors are at play besides genetics.
Understanding the link between genetic features and biological characteristics could be a game changer in healthcare. For instance, if doctors could predict that a patient has a high risk of developing a specific disease, they could create a treatment plan that reduces this risk before symptoms emerge.
The method developed in this study shows that polygenic scores can predict complex biological characteristics, at least in some cases. “As our knowledge expands, polygenic scores, despite their drawbacks, will become more and more informative about the risk for disease,” suggests Kauwe. “We will be able to use these scores to predict that risk in the future.”
Corinne E. Sexton, Mark T. W. Ebbert, et al., “Common DNA Variants Accurately Rank an Individual of Extreme Height”, International Journal of Genomics, vol. 2018, Article ID 5121540, 7 pages, 2018. https://doi.org/10.1155/2018/5121540.