PARIS: The first gene that helps explain common differences in height has been elucidated.
Just a single base change in one gene’s DNA code determines whether people will be taller or shorter by up to one centimetre, said researchers, adding that hundreds of other genes are also likely to play a role in height.
Genes have long been known as the driver of height; everyone knows that a child whose parents are both tall is also likely to grow up tall, too. Unlike obesity, where genes and environmental factors – nutrition and exercise for example – play a joint role, around 90 per cent of the determinants for height are thought to be genetic.
Probing the link
Even though the link is clearly there, finding ‘height’ genes that are common across the population has been strangely elusive. Until now, the only evidence has been spotted among a small group of people with a rare condition that affects their stature.
Now, in a paper published by the journal Nature Genetics, British and U.S. reveal their results from a DNA analysis of nearly 5,000 people of European descent. Mainly individuals living in Britain, Sweden and Finland.
The exhaustive trawl threw up a gene called HMGA2.
The change of just a single base letter in HMGA2′s genetic code – a ‘C’ (for cytosine) instead of a ‘T’ (for thymine) – adds nearly a centimetre in height to people who inherited this variant from both parents. Those who got the ‘C’ variant from only one of their parents were about half a centimetre taller than their ‘T’ counterparts.
After comparing this discovery to further studies of nearly 30,000 other people, the team believe around a quarter of people of European descent carry the double C variant.
Around a quarter have the double T version, thus leaving them about a centimetre shorter than their double C counterparts. Many other genes remain to be uncovered, for HMGA2 explains only 0.3 per cent of the variability in human stature.
Regulating cell growth
“Height is a typical ‘polygenic’ trait, in other words many genes contribute towards making us taller or shorter,” said lead researcher Tim Frayling of the Peninsula Medical School in Exeter, in the southwest of England. “Clearly, our results do not explain why one person will be six feet five inches and another only four feet 10 inches. This is just the first of many that will be found, possibly as many as several hundred.”
Another step is to explain why HMGA2 has this effect. Researchers believe it plays a role in growth through regulating cell growth.
Interest in height genes is spurred by more than idle curiosity, for there could also be a windfall in knowledge about disease. Taller people are statistically more likely to be at risk from some kinds of cancer (prostate, bladder and lung, for instance), which implies that genes that regulate cell multiplication may also play some part in letting cancer cells proliferate. Statistics also throw up an association between shortness and heart disease.
“This is the first convincing result that explains how DNA can affect normal variation in human height,” commented Joel Hirschhorn of the Broad Institute in Massachusetts, U.S., also a professor of genetics at Harvard Medical School. “Because height is a complex trait, involving a variety of genetic and non-genetic factors, it can teach us valuable lessons about the genetic framework of other complex traits, such as diabetes, cancer and other common human diseases.”