SNPwatch: Large Studies Find SNPs with Small Effects on Height

SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.

tallshadow2.jpgThree articles published online this week in the journal Nature Genetics report a bumper crop of SNPs associated with human height.

Unlike other physical characteristics such as obesity that are caused by a mix of genetic and environmental factors, 90% of normal variation in human height is due to DNA alone. But unraveling the details of the genetics has been difficult.

Last year, two large studies (here and here) looked for SNPs associated with height. Only two convincing candidates were found, and each of them accounted for only about a half-centimeter difference in height.

The three new studies (here, here, and here) were able to find more SNPs associated with height by using extremely large sample sizes — two of the studies had more than 30,000 participants and the third study looked at more than 15,000 people. Large sample sizes increase the chance that SNPs with small effects will be found.

Like the previously found height SNPs, the new SNPs each individually account for only a fraction of a centimeter in height difference.

The authors of all three papers note that statistical analyses of their data indicate that many more small effect SNPs are waiting to be found. Even bigger sample sizes may be necessary to detect these SNPs.

Many of the SNPs associated with height are in genes with well-documented functions in processes such as cell division, cell-to-cell signaling, and gene regulation. Other SNPs, however, are in genes about which little is known.

“There may be more than a hundred genes which affect our height, many of which will work in surprising or unpredicted ways,” said Mike Weedon, lead author of one of the papers.

“The challenge now for us is to understand how they influence growth in the body. This could open up new avenues for treating a range of diseases,” said Weedon.

Want to know how you stack up?

23andMe users can see their data for 46 distinct height-related SNPs in the Genome Explorer (now called Browse Raw Data) (in some cases we substitute a SNP from the three new studies with an equivalent one that is included on our chip).

We’ve used the data in each paper to calculate the approximate effect in centimeters for each SNP. The effect shown is the increase in height (in cm) that each copy of the “tall” version of the SNP would give a person compared to someone who had two “short” versions. At this point, these findings apply only to people of European ancestry.

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Photo by Dave2003/istockphoto