Researchers have identified five of the genes that shape a person's face, work that could help scientists better understand facial abnormalities like cleft palate and someday might even help forensic investigators determine what a criminal suspect looks like from crime-scene DNA.
Researchers previously knew that genetics played a large role in determining face shape, since identical twins share DNA. However, little was known about exactly which genes are involved. Three genes were thought to have roles in the arrangement of facial features, and the new research confirmed their involvement. It also identified two other genes.
"We are marking the beginning of understanding the genetic basis of the human face," said lead researcher Manfred Kayser, head of the forensic molecular biology department at Erasmus MC-University Medical Center Rotterdam, Netherlands.
The study is part of the work of the International Visible Trait Genetics (VisiGen) Consortium, a group of six researchers who want to understand the genetics behind visible human characteristics. [Genetics By the Numbers: 10 Tantalizing Tales]
Using magnetic resonance imaging, Kayser and colleagues scanned the heads of 5,388 volunteers of European descent to create three-dimensional maps of each face. The group analyzed the genomes of participants with over 2.5 million DNA markers each to determine which genes could help explain any of the 48 facial characteristics under consideration, such as the distance between the eyes and the nose.
Pictures of 3,867 other subjects were used to verify any identified genetic associations linked to face shape.
The gene hunt confirmed three genes thought to be involved in face shape — called PRDM16, PAX3 and TP63 — plus two genes, dubbed C5orf50, and COL17A1, previously not known to play a role in facial structure.
"The most surprising thing is that we did find genes," Kayser told LiveScience. "To ever actually reach the level to start to understand the human face, I would not have imagined it eight years ago," when he started this line of work.
Experts cautioned that the exciting prospect of painting a portrait using DNA as a guide is still a long way off.
"Like height, we expect that face shape is influenced by many hundreds/thousands of genes with small effects," Lavinia Paternoster, a genetic epidemiologist at the University of Bristol, wrote in an email. "So although we are starting to understand what influences how the human face develops, we are nowhere near a position whereby we can predict a human face from someone's genetic code."
Paternoster, who is not involved in the current study, was part of the research team that found PAX3 was involved in nasion, the position of the top of the nose, as part of the Avon Longitudinal Study of Parents and Children (ALSPAC). Kayser's research confirmed the role of PAX3 in nose position.
PAX3, a gene that regulates muscle-cell formation, controls the distance between the top of the nose and the right and left eyes. People with mutations in PAX3 develop Waardenburg syndrome, a rare genetic disorder characterized by wide-set eyes.
"We use different face-scanning technology in ALSPAC, so the fact that this gene was discovered using both techniques is encouraging for future collaborations," Paternoster wrote. The confirmation was also notable because one group examined children, while the other analyzed samples from adults.
Mutations in PRDM16, a key gene in the body’s switch between available and stored fats, cause cleft palate in mice; mutations in TP63 cause "acro-dermato-ungual-lacrimal-tooth," a rare disease that affects multiple parts of the body and is characterized by missing teeth, thin skin, and extensive freckling. [The 9 Weirdest Medical Conditions]
COL17A1 encodes for a collagen gene that, when mutated, causes blistering. Almost nothing is known about the fifth gene, C5orf50.
The curiosity-fueled research has a potential application for forensic investigations in the distant future, the researchers said. Facial descriptions from DNA could prove more reliable than witness accounts at crime scenes, which are limited by human memory and perception.
Currently, however, using DNA samples to recognize a suspect is currently a "far-fetched, 'CSI'-like scenario," Kayser said.
It's a little less far-fetched in the case of eye and hair color. Kayser and colleagues in August released HIrisPlex, a system that allows researchers to predict eye and hair color from DNA samples, although only from people of European descent. The forensic test is nearly 70 percent accurate in identifying blonds and up to 87.5 percent accurate for dark-haired individuals.
In the future, Kayser expects to look at more facial features, especially since the face scans stopped at the nose and excluded the lower face. He also expects to look at more landmarks on the face. The current study examined nine points on the face, although many more exist.
The VisiGen team also is planning to collaborate with the Bristol researchers, since having a larger sample size will allow the investigators to find genes that have smaller effects.
"We are rather at the beginning, where it is not quite clear if this forensic tool can be used with accuracy; this is still in question whether it's possible," Kayser said.
The study is detailed today (Sept. 13) in the journal PLoS Genetics.