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The Scientific American recently showed that genetics predominantly determines human height. And only a small portion affected nutrition and other environmental factors. According to the report, “60% to 80% of the difference in height between individuals is determined by genetic factors, whereas 20% to 40% can be attributed to environmental effects, mainly nutrition. This answer is based on estimates of the ‘heritability’ of human height: the proportion of the total variation in height due to genetic factors.”

Heritability allows researchers to examine the impact of genetics on a person’s height. Recently, a team of Harvard scientists was able to isolate the genes that contribute to a person’s height. They used precision medicine that looks at individual variability in genes.

This bold discovery can do more than make individuals taller in the future. It could be the key to understanding more complicated genetic problems and finding a cure for them.

Headed by Terence Capellini, Associate Professor of Human Evolutionary Biology, the team has been working on “switches” that could influence height. They also experimented on how these switches alter the function of a key height gene.

“Large genome-wide association studies on upwards of 250,000 people found about 700 genetic regions associated with height,” Capellini said in a Science Daily report. “But within each region there could be many single DNA variants linked together, so there are potentially tens of thousands of variants spanning those regions. The question is how do you whittle that number down to those specific variants that influence height?”

Filtering Genetic Variants

Individual height differences
Individual height differences

There are over 60,000 genetic variants that can affect that cartilage growth plate of bones. Capellini’s team needed to filter which ones directly affected the cartilage growth plates. These are areas in the long bones of the legs and arms that produce new bones. Interestingly, they lengthen as children grow. This means that when the switch is off, the genes can help bone growth and length. This will result to taller individuals.

The scientists tracked down “switches” responsible for causing neighboring genes to turn on and off.

The process was long and tedious, requiring several quality control tests. Michael Guo, one of the study’s co-authors, brought down the 60,000 possible genetic variants to 900.

“We also looked at switches from other cell types to see if these genetic variants appeared, and they didn’t. That really suggests to us that the signals we’re seeing are very strong, it’s not just a property of the genome or a property of identifying these switches,” the study read.

Isolating the Switches

Chondroitin Sulfate Synthase 1 or CHSY1 is the gene responsible for cartilage hardening into bone. Scientists determined that it influences the length of the thigh bone or femur in humans and mice.

When the researchers removed the switch and its variant from human cartilage cells, they saw an increased expression of the gene. These findings can create a big impact to further understanding of the role of genes in human height. The team plans to develop more methods to test other gene variants and determine their effects on height.

In-depth studies will allow scientists to better understand other conditions affected by both genetics and environment. These include heart ailments, diabetes, and even cancer. Importantly, understanding what switches trigger certain genes could lead to treatments or a cure.

Capellini said:

For any disease or trait, being able to say here is a switch that turns a gene on or off, and here is the mutation in that switch that can effect it dramatically…that’s pretty powerful.

That will allow us figure out what are the biological pathways that are worth targeting. The future of personalized medicine will rely on knowing what specific pieces of DNA are doing in the body, and this is one way to do that.”

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