When you look at yourself in the mirror, do you ever wonder why you look the way you do? Do you also wonder what biological processes were at work when it came time to shape and sculpt your face, which is as individual and unique as a fingerprint?
The answer is in a little snippet of your DNA called a gene enhancer, according to scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab)
These little pieces of DNA help switch on, or boost the expression of specific genes that control the development of the face and head while in utero. What’s interesting about these little influential bits of DNA is that a gene enhancer doesn’t have to be found anywhere close to the genes it works on and, in some cases, doesn’t even have to be located on the same chromosome.
Of course, there are a number of hereditary factors, such as when a child resembles a parent, that help determine appearance. The researchers, who outlined their findings in the journal “Science,” said the gene enhancer fine-tunes the genetics to give your face its final unique look. Even with identical twins, there are subtle differences in appearance.
“Our results suggest it is likely there are thousands of enhancers in the human genome that are somehow involved in craniofacial development,” said Axel Visel, a geneticist with Berkeley Lab’s Genomics Division, who led the research. “We don’t know yet what all of these enhancers do, but we do know that they are out there and they are important for craniofacial development.”
Scientists have previously been able to identify some of the genetic flaws that can cause birth defects, such as a cleft lip or palate, but haven’t been able to fully understand what genetic factors are responsible for normal, subtle differences in appearance.
In the past, Visel and his colleagues were able to map gene enhancers in the heart, brain and other vital organs. The researchers said their studies showed that gene enhancers can control their targets from across distances of hundreds of thousands of base pairs, which are each two chemical bases that scientists consider to be the fundamental components of the DNA double helix.
To find out if these gene enhancers have the same type of long-distance effect on the development of the head and face, the researchers studied transgenic mice or those that had been genetically modified.
They were able to identify more than 4,000 possible gene enhancer sequences they think play a role in fine-tuning the genes responsible for developing and defining the head and face.
A later analysis of their data showed that removing a few of these individual craniofacial enhancers can cause changes to the shape of the head and/or face.
“Our results also offer an opportunity for human geneticists to look for mutations specifically in enhancers that may play a role in birth defects, which in turn may help to develop better diagnostic and therapeutic approaches,” said Visel.
While the researchers continue their own research, they are also working with geneticists to carry out specialized searches to look for mutations within the enhancer sequences of humans with craniofacial birth defects.