Seth M. Weinberg and John R. Shaffer - The Conversation
You might think it is pretty obvious that your facial appearance is determined by your genes.
Just look in the family photo album and observe the same nose, eyes or chin in your grandparents, cousins or uncles.
Perhaps you have seen or know someone with a genetic syndrome, which is often the result of a harmful alteration in one or more genes, and yet noticed their distinctive facial features.
You might be surprised to learn that, until very recently, geneticists practically did not understand which parts of our DNA were linked to the most basic aspects of facial appearance.
This gap in our knowledge was particularly irritating as
facial appearance plays a key role in basic human interactions
.
The availability of large data sets that combine genetic information with facial images have revealed great discoveries.
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What do we know about the genetics of facial appearance?
Can we reliably predict a person's face from their DNA?
What are the implications for health and disease?
We are an anthropologist and human geneticist whose research focuses on uncovering the biological factors that underlie the similarities and differences in facial appearance between humans.
How many genes are associated with facial appearance?
We do not yet have an answer to this question, but work recently published in Nature Genetics by our collaborative research team has identified more than 130 chromosomal regions associated with specific aspects of facial shape.
Identifying these regions is a critical first step in understanding how genetics impacts our faces and how that knowledge could affect human health in the future.
We achieve this by scanning the DNA of more than 8,000 individuals to look for statistical relationships between approximately seven million genetic markers
, known locations in the genetic code where humans vary, and dozens of shape measurements derived from 3D facial images.
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When we find a statistical association between a facial feature and one or more genetic markers, this points us to a very precise region of DNA on a chromosome.
The genes located around that region become our main candidates for facial features such as the shape of the nose or lips, especially if we have other relevant information about their function, for example, they may be active when the face is forming in the embryo.
While more than 130 chromosome regions may seem like a large number, we are probably just scratching the surface.
We expect thousands of those regions, and therefore thousands of genes, to contribute to facial appearance.
Many of the genes in these chromosomal regions will have such small effects that we may never have enough statistical power to detect them.
What do we know about these genes?
When we collectively looked at the genes involved in these more than 130 regions of DNA, some interesting patterns emerged.
Your nose, whether you like it or not, is the part of your face most influenced by your genes.
Perhaps not surprisingly, areas like the cheeks, which are heavily influenced by lifestyle factors like diet, showed the fewest genetic associations.
Supermodel Cindy Crawford and her daughter, Kaia Gerber, during an event in Beverly Hills, California on November 6, 2019. Kaia undoubtedly inherited her nose from her mother.Axelle / Bauer-Griffin / FilmMagic
The way these genes influence facial shape was not entirely uniform.
We found that some genes had very localized effects and impacted very specific parts of the face, while others had broad effects that involved multiple parts.
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We also discovered that a large proportion of these genes are involved in basic developmental processes that build our bodies (bone formation, for example) and, in many cases, they are the same genes that have been implicated in rare syndromes and facial abnormalities. like a cleft palate.
We found it interesting that there is a high degree of overlap between genes involved in limb and facial development
, which may provide an important clue as to why many genetic syndromes are characterized by malformations of both the hand and the face.
In another curious twist, we find some evidence that genes involved in facial shape may also be involved in cancer, an intriguing finding given the emerging evidence that individuals treated for pediatric cancer display some distinctive facial features.
Can someone take my DNA and build an accurate image of my face?
It is unlikely that today, or in the foreseeable future, someone will be able to take a sample of your DNA and use it to build a picture of your face.
Predicting the facial appearance of an individual, like any complex genetic trait, is a very difficult task.
To put that statement in context, the more than 130 genetic regions we identified explain less than 10% of the variation in facial shape.
However, even if we understood all the genes involved in facial appearance, prediction would still be a monstrous challenge.
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This is because complex features like facial shape are not determined simply by summarizing the effects of a group of individual genes.
Facial features are influenced by many biological and non-biological factors: age, diet, climate, hormones, trauma, illness, sun exposure, biomechanical forces, and surgery.
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All of these factors interact with our genome in such complex ways that we haven't even begun to understand.
To add to this picture of complexity, genes interact with each other;
This is known as "epistasis" and its effects can be unpredictable.
Not surprisingly, then, researchers who tried to predict individual facial features from DNA have not been successful.
This is not to say that such a prediction will never be possible, but if someone tells you that they can do this today, you must be very skeptical.
How might research connecting genes and faces benefit humans?
One of the most exciting advances in medicine in the 21st century is the use of patients' genetic information to create personalized treatment plans, with the ultimate goal of improving health outcomes.
A deeper understanding of how genes influence the time and rate of facial growth could be an invaluable tool
for planning treatments in fields such as orthodontics or reconstructive surgery
.
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For example, if we can one day use genetics to help predict when a child's jaw will reach its maximum growth potential, orthodontists can use this information to help determine the optimal time to intervene.
Likewise, knowledge of how genes work individually and together to determine the size and shape of facial features may provide new molecular targets for drug therapies aimed at correcting facial growth deficiencies.
Finally, a greater understanding of the genes that make up human faces can offer us
new insights into the root causes of congenital facial malformations
, which can have a profound impact on the quality of life of those affected and their families.