By Seth M. Weinberg, University of Pittsburgh and John R. Shaffer, University of Pittsburgh
- A new study shows that more than 130 regions in human DNA play a role in the design of facial features.
- The nose is the facial feature that is most influenced by your genes.
- Understanding the relationship between certain genes and facial features can be helpful in treating facial malformations or in orthodontics.
You might think it’s pretty obvious that your genes determine your facial expression. Just look in the family photo album and observe the same nose, eyes or chin in your grandparents, cousins, uncles and aunts. You may have seen or known someone with a genetic syndrome – which often results from a harmful change in one or more genes – and noticed their often distinctive facial features.
You will be surprised to learn that until recently geneticists had virtually no understanding of what parts of our DNA were linked to the most basic aspects of facial expression. This knowledge gap was particularly annoying because the appearance of the face is so important in basic human interactions. The availability of large amounts of data that combines genetic information with measurable facial images has rapidly accelerated the pace of discovery.
What do we know about facial expression genetics? Can we reliably predict a person’s face based on their DNA? What are the effects on health and disease? We are an anthropologist and human geneticist whose research is focused on uncovering the biological factors that underlie the similarities and differences in facial expression in humans.
How many genes are linked to the appearance of the face?
We don’t have a complete answer to this question yet, but work recently published in Nature Genetics by our collaborative research team identified more than 130 chromosomal regions associated with certain aspects of face shape. Identifying these regions is a crucial first step in understanding how genetics affect our faces, and how that knowledge could affect human health in the future.
We did this by scanning the DNA of more than 8,000 people to look for statistical relationships between roughly seven million genetic markers – known locations in the genetic code where humans vary – and dozens of shape measurements derived from 3D facial images were looking for.
When we find a statistical association between a facial feature and one or more genetic markers, it indicates a very precise region of DNA on a chromosome. The genes in this region then become our main candidates for facial features such as nose or lip shape, especially when we have other relevant information about their function – for example, they can be active when the face is forming in the embryo.
While more than 130 chromosomal regions may seem like a large number, we are probably just scratching the surface. We expect thousands of such regions – and therefore thousands of genes – to contribute to the appearance of the face. Many of the genes in these chromosomal regions will have so little impact that we may never have enough statistical power to detect them.
What do we know about these genes?
If we look together at the genes involved in these 130+ regions of DNA, some interesting patterns emerge.
Your nose, like it or not, is the part of your face that is most influenced by your genes. Perhaps unsurprisingly, areas like the cheeks, which are heavily influenced by lifestyle factors like diet, had the fewest genetic associations.
The way these genes affect face shape was not at all uniform. We found that some genes had highly localized effects affecting very specific parts of the face, while others had wide-ranging effects affecting multiple parts.
We also found that a large number of these genes are involved in the basic developmental processes that build our bodies – such as bone formation – and in many cases are the same genes that have been involved in rare syndromes and facial abnormalities such as cleft palates.
We found it interesting that there was a high degree of overlap between the genes involved in face and limb development, which may provide an important clue as to why many genetic syndromes are characterized by both hand and facial malformations. In another curious twist, we found some evidence that the genes involved in face shape may also be involved in cancer – a fascinating finding given the emerging evidence that people treated for childhood cancer have some distinctive facial features.
Can someone take my DNA and create an accurate picture of my face?
It is unlikely that anyone will take a sample of your DNA and create an image of your face today or for the foreseeable future. Predicting an individual’s facial expression, like any complex genetic trait, is a very difficult task.
To put that statement into context, the 130+ genetic regions we’ve identified account for less than 10% of the variation in face shape. Even if we understood all of the genes involved in the appearance of the face, predicting it would still be daunting. This is because complex traits like face shape are not determined by simply aggregating the effects of a number of individual genes. Facial features are influenced by many biological and non-biological factors: age, diet, climate, hormones, trauma, illness, exposure to the sun, biomechanical forces, and surgery.
All of these factors interact with our genome in complex ways that we don’t even understand. To complete this picture of complexity, genes interact with each other. This is known as “epistasis” and its effects can be complex and unpredictable.
It is therefore not surprising that researchers who tried to predict individual facial features from DNA were unsuccessful. This does not mean that such a prediction will never be possible, but if someone tells you they can do it today, you should be extremely skeptical.
How could research linking genes and faces benefit humans?
One of the most exciting developments in medicine in the 21st century is the use of patient genetic information to create personalized treatment plans with the aim of improving health outcomes.
[Deep knowledge, daily. Sign up for The Conversation’s newsletter.]
A deeper understanding of how genes affect the timing and rate of facial growth could be an invaluable tool for planning treatments in areas such as orthodontics or reconstructive surgery. For example, if one day we can use genetics to predict when a child’s jaw will reach its maximum growth potential, orthodontists may be able to use this information to determine the optimal time to intervene for maximum effect.
Likewise, knowing how genes work individually and collectively to determine the size and shape of facial features can provide new molecular targets for drug therapies to correct facial growth deficiencies.
Ultimately, better understanding of the genes that make up human faces can provide us with new insights into the causes of congenital facial malformations that can seriously affect the quality of life of those affected and their families.
Seth M. Weinberg, Associate Professor in the Oral Biology, Human Genetics and Anthropology Departments. Co-directors of the Center for Craniofacial and Dental Genetics at the University of Pittsburgh and John R. Shaffer, Assistant Professor of Human Genetics at the University of Pittsburgh
This article is republished by The Conversation under a Creative Commons license. Read the original article.